Friction stir processing (FSP) at 1120 rpm was performed to refine surface characteristics of a magnesium alloy which included tri-calcium phosphate. Hardness tests showed that measurements of average hardness and the hardness of the surface layer have been significantly altered by the dispersed nanoparticles. Due to the deposition of greater Ca/P mineral phase, the FSP ZM21 saw less weight loss than the unprocessed alloy during immersion test investigations conducted in simulated body fluids (SBFs) in 24 hours. As demonstrated by the results of the tensile testing, the FSP ZM21 alloy had a greater ultimate tensile strength than the parent alloy. Additionally, the tensile specimens were tested after being subjected to the corrosive medium SBF for 24 hours. Results indicate an enhanced effect of grain refinement, reduced intermetallic phase, and development of supersaturated grains on retaining the improved mechanical characteristics following degradation.
Research Article
Study of mechanical characteristics and microstructure on ZM21 alloy with Tricalcium Phosphate using Friction stir processing
https://doi.org/10.21203/rs.3.rs-3611769/v1
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Friction stir processing
Mg ZM21
Biodegradability
Due to non-toxicity, beneficial biodegradability and biocompatibility, magnesium alloys and their derivatives have piqued the interest of numerous researchers in recent years (1). Magnesium and its alloys have Young's moduli that are notably close to those of natural bone when compared to the standard metallic materials, suggesting that stress shielding could be minimized. Unlike conventional metallic implants, Magnesium alloy implants may be entirely degraded following bone tissue healing, so removal surgery is not needed (1, 2). However, earlier studies have shown that magnesium has a rapid corrosion rate, especially in early stages of disintegration (3). Hydrogen foams and surface alkalization can impact tissue growth, according to (4). In order to prevent rapid corrosion during the initial phase of magnesium alloy degradation, the surface must be modified. Various commonly used procedures, such as surface coating(5, 6) ion implantation (6, 7), and laser surface melting (8, 9), can be employed to modify the surface. These procedures are challenging to implement because metallurgical imperfections are avoided by minimizing the intense chemical interactions between reinforcements and matrices. Microstructure modifications at the surface or the creation of MMCs from aluminium, copper, magnesium, and titanium are possible with friction stir processing (FSP)(10) Plasma spraying, powder metallurgy and laser-assisted processes are the most prevalent methods for making MMCs. Material transformations occurred due to high temperatures, and unfavourable interactions occurred between the base metal and additives throughout these processes. FSP is an advantageous solid-state processing method since it avoids the possible limitations of traditional liquid-phase processing. While a rotating tool is inserted into a plate and then moves along a predetermined path, it creates significant plastic deformation and localized heating. This makes it easy to refine grains through dynamic recrystallization.(11). Dentists have a wide variety of bone substitutes at their disposal. These ceramics are consisting of calcium phosphate ceramics that resemble mineral phase of bone, such as tri-calcium phosphate (TCP Ca3[PO4]2) or hydroxyapatite (HACa5[OH(PO4)3]) (12). TCP possesses excellent biocompatibility, favourable degradation properties, and osteoconductive, making it a suitable bone replacement (13, 14). Specifically, the calcium-to-phosphorus ratio of TCP is 1.5 (15). In vivo, partially amorphous β-TCP is more osteoconductive than HA and biodegradable than crystalline β-TCP. It can crystallize in either a rhombohedral form at high temperatures (α-TCP) or a monoclinic form at low temperatures (β-TCP) (14, 16). Further, the adhesion between the coatings and substrates will be significantly influenced when electrolyte permeates the coatings through a significant crevice and corrodes magnesium substrates.(17) Due to their compatibility with a variety of additives, the fabrication of MMCs is described as an alternate, advantageous method in numerous published pieces of literature. Bioactive elements such as calcium and phosphorus are commonly employed as reinforcing agents in magnesium alloys to reduce corrosion and improve biocompatibility. Most studies addressing the production of MMCs by FSP employed rotational speeds from 1000 to 2000 rpm, which might have contributed to an irregular dispersal of powder particles over the surface and altered the MMCs' properties. Magnesium was deployed as the base metal in this study since it contains non-toxic Zn and Mn components. The ZM21-ß-TCP composite was manufactured using FSP at 1120 rpm. Research into the influence of FSP rotational speed and ß-TCP content on ZM21 magnesium matrix corrosion behaviour was the subject of this research.
2.1. Materials and processing
The ZM21 wrought magnesium alloy plate with dimensions of 80 mm, 70 mm 10 mm was manufactured, whose Composition is Mg bal., 2.0 Zn, 1.0 Mn (wt.%). FSP tool was manufactured from H-13 tool steel with a thickness of 10 mm, length of the pin was 3.5 mm. Because of these considerations, the magnesium alloys used in the samples collected retain their non-toxicity, biodegradability, and biocompatibility features, which were initially intended to be preserved.
The processing parameters were optimized to achieve defect-free samples by maintaining rotational speed at 1120 rpm with a traverse speed of 10 mm/min. To perform FSP vertical milling machine was used. A slot was created with a 1.5 mm width with 2.5 mm depth on surface of a sheet. In order to prevent the ß-TCP powder from spreading out during the FSP, a pin less tool was used to cover the groove top opening after the powder was placed in the groove (Fig. 1(a) and 1(b)). The 16 mm shoulder diameter of the hardened H-13 tool steel was used to make the pin-less tool. Weighing the sheet before and after ß-TCP was placed in the groove enabled us to determine the weight fraction of ß-TCP that had been applied. The stir zone's cross-sectional area was determined using macrographic images. While retaining the volume of the processed zone, the mass of embedded ß-TCP and the density of the ZM21-ß-TCP and FSP ZM21 composites were produced.
2.2 Characterization of Microstructures
Cross-sections were taken perpendicular to processing direction to examine sample’s microstructure. As per the conventional metallographic process, they were polished with a 0.5 µm diamond paste after being ground with 2000 grade Silicon Carbide sheets. Microstructure analysis was required using an oxalic acid reagent, which was applied to the samples after they had been etched with nitric acid/oxalic acid solution (1 g/1.5 ml) and water for 4–6 seconds, respectively. Scanning electron microscopy (SUPRA − 55 ZEISS) and an Optical microscope (OLYMPUS PMG-3, Japan) equipped with an X-ray energy dispersive spectroscopy were utilized to identify Composition and structure of corrosion-damaged surfaces. XRD analysis equipment (X- Pert PRO MPD, PAN-alytical) was used to describe the specimens.
2.3 Mechanical Characterization
2.3.1 Hardness testing
The HMV-1 Vickers microhardness measurement (Leitz, Germany) and its methodologies were utilized to ascertain the hardness of magnesium alloys and synthesized nanocomposites. A load of 0.98 N for 15 s was applied. Sample’s transverse surfaces had their hardness distribution and average values tested at intervals of 0.5 mm.
2.3.2 Tensile Test
Tensile tests were performed at room temperature (Zwick Roell, Germany) with a strain rate of 0.01 s− 1 using specimens prepared under ASTM E8 (18). Degradation of ZM21 and FSP ZM21 was studied by subjecting specimens to a uniaxial tensile test before and after being submerged in SBF for 24 hours, rinsing them with distilled water, and allowing them to dry. The gauge length of the specimens prepared was submerged in SBF, while the remaining regions were protected with plastic tape to prevent corrosion damage to the sections that would have been required to be held in grippers throughout the tensile test. Results of a tensile test on an FSP ZM21 submerged sample are displayed in Fig. 4, accompanied by the dimensions of the specimens and a representative image.
2.4 Corrosion Behaviour
2.4.1 Immersion test degradation
Samples were submerged in SBF 5x (500 ml each) for 24 hours to measure weight loss. Pieces were immersed in a solution of chromic acid at 37°C, to eliminate corroded substrates, subsequently rinsed in deionized water and dried in the open air. After 24 hours in a solution, the pH was measured to see shifts in ionic concentration due to degradation. Finally, corrosion rate (CR, mm/year) was determined using following equation below based on weight loss. (19)
CR = 8.76 x 104 w / a t ρ
In above equation, ‘a’ represents the initial sample surface area in square centimetres, ‘w’ represents the weight loss in grams, ρ represents the sample density in grams per cubic centimetres, and ‘t’ is the period in hours that the sample was immersed. The density of all samples, including those used in cross-sectional studies, is set at 1.74 g/cm3. The corrosion topography was analysed using an Amary 1000A EDX spectrometer and a JEOL JSM 6335F FESEM.
2.4.2 Electrochemical Analysis
The corrosion behaviour of tested specimens was investigated using simulated bodily fluid (SBF). Table 1 depicts the reagents needed to make SBF (20). Tests were carried out at 37°C in SBF buffered at PH = 7.4 for electrochemical testing. A three-electrode setup was chosen for the electrochemical cell, including a platinum network counter electrode, an Ag/AgCl reference electrode, and a working electrode for the samples. SiC sandpaper was used to sand all specimen surfaces down to 1500 grade. One square centimetre was used to assess specimens in the SBF. Concerning time-dependent open circuit potential measurements, the sample's OCP in the SBF was recorded promptly.
Table 1 Amount of reagent for preparing 1000 ml of SBF solution (20).
3.1. Optimization of processing parameters
Figure 5 shows the variation in ß-TCP powder dispersion in base metal as a function of processing parameters. To make metal matrix composites, the majority of studies have used FSP with slower rotating and processing speeds (19). However, it's possible that microscopic cracks and banded structures of additives formed in the base metal as a result of insufficient heat input and poor material movement. The rotating speed of the tool was 1120 rpm, and the traversal speed was maintained at 10 mm/min with a single pass to find out how the two variables affected the ß-TCP distribution.
3.2. Microstructure
Magnesium alloy and its composite microstructure are depicted in Fig. 6. Figure 6(a) shows the typical grain size distribution of ZM21, which ranged from 150 to 300 µm. Grains of varying sizes also lowered the matrix's corrosion resistance and mechanical characteristics. There is no evidence that FSP ZM21 crystallite size dropped by more than a hundred times to just eight µm (Fig. 6(b)). Because of the high strain rate associated with the process of dynamic recrystallization (21, 22) as well as the blockage of dislocation movement with high density [29], FSP was found to improve grain refinement (23) significantly. Grain development in ZM21-ß-TCP composites was significantly reduced because of the pinning factor of the distributed ß-TCP aggregates. By using a scanning electron microscope (SEM), we were able to see how the ß-TCP particles were distributed throughout the magnesium substrate (Fig. 6(d)). A revolving pin and a moving tool shoulder were used to create onion rings due to the mixing power used in the FSP process. In the meantime, ß-TCP particles were disseminated in a plastic material flow. Onion rings are generated as a result of friction heating caused by tool's rotation and forward movement, which extrudes metal to tool's retreating side in stir zone during FSP which shows the constancy of flow of the material is a well-known phenomenon that has been extensively examined (24, 25). Even though the matrix was filled with numerous white particles, none could be seen clustered together, as shown in Fig. 6(d). EDS analysis indicates that all these white pieces consist of calcium and phosphorus, demonstrating that ß-TCP particles have been integrated into the magnesium alloys to generate ZM21-ß-TCP composites. Experimentation with EDS on SZ revealed high calcium and phosphorus concentrations except in the matrix elements; the densities were close to each other in the SZ, suggesting uniform distribution. The ß-TCP particles were disseminated across the stir zone due to the one-pass FSP.
3.3. Phases Composition
XRD analysis results (Fig. 8) conducted before immersion tests showed that FSP samples were easily distinguished from ZM21 magnesium alloy by their stronger diffraction peaks. Highly high intensities were seen in the surfaces of FSP samples (0002), whereas the maximum intensities in the planes of the (1120) had the lowest peak for as-wrought ZM21 magnesium alloy (Fig. 8(a)). The shoulder and pin of the rotating tool were observed to have an impact on the textural distribution within the stir zone of FSP samples. Nevertheless, the motion of a rotating pin can affect every region of SZ, resulting in the formation of shear deformation planes of (0002) in the matrix. These planes align with an ellipsoidal surface that is cantered on the pin. (26). It has been demonstrated that the surface energies of the Mg planes (0001) and (1120) are 2.059 eV/nm2 and 1.608 eV/nm2, respectively (27).
Magnesium alloy dissolution is slowed, and corrosion resistance is improved due to the significantly low surface energy of (0002) surfaces in FSP samples. According to XRD results (Fig. 8(b)), FSP reduced the amplitude of peaks representing the first MgZn2 phases. This was due to the fact that a constant temperature was maintained due to frictional heating, and the interdiffusion was accelerated owing to the effect of mechanical activation brought on by a severe plastic deformation (28). The FSP was shown to be responsible for transforming the original MgZn2 phases into additional intermetallic phases, which are predicted to be more uniformly diffused in fine grain.
3.4 Characterization Based on Mechanical Methods
3.4.1 Microhardness
Data regarding the samples' microhardness and average microhardness distribution is depicted in Fig. 9(a) and 9(b). The grain refinement strength of magnesium alloy, which FSP processed, resulted in an improvement in microhardness. However, it has yet to be to a substantial level. A considerable increase in hardness was seen in the ZM21-ß-TCP composites, showing that the integration of ß-TCP was the primary source of the improvement. The amount and distribution of ß-TCP in magnesium alloy significantly influenced the alloy's microhardness. The variation in microhardness levels shows the dispersion of ß-TCP particles. Microhardness in SZ is thought to be affected by the greater particle density in the onion rings than in the spaces between them. Magnesium alloy's average microhardness increased in tandem with the addition of ß-TCP. According to the results, the ß-TCP in the substrate was found to influence mechanical characteristics of the Mg matrix.
3.4.2. Tensile test
The mechanical properties in Table 2 are calculated from the stress-strain curves shown in Fig. 10. It is well-established that a material's strength increases as its grain size decreases. Grain size is particularly significant (27) in improving mechanical properties in metals, along with other microstructural characteristics as twins, dislocations, and intermetallic. The FSP ZM21's hardness is drastically different from that of the original material due to microstructural modifications. The tensile properties have been marginally enhanced by the microstructure modification, however. Reinforcement at the grain boundaries is largely responsible for the increased strength of fine-grained materials. The contrary is true for Mg alloys, wherein the strength is diminished by a decrease in the amount of secondary phase. (29)
Changing metal matrix size and form at grain boundaries degrades FSP ZM21 alloy's bulk mechanical behaviour. Supersaturated grains enhance FSP ZM21's tensile strength. Marginal improvement in FSP ZM21 Mg alloy results from grain refining, reduced intermetallic phase, and supersaturated grains.
Defects on the material's surface, like cracks or pores, reduce its strength and can even cause a fracture to start suddenly. Failure is generally initiated by stress concentration zones, such as the cracks and pits in the surface that form due to corrosion. Unchecked corrosion in a physiological environment causes pitting and micro cracking on surface of Mg alloys. Therefore, it is essential to evaluate mechanical behaviour of the implant throughout degradation by studying how Mg alloys behave mechanically after being exposed to a corroding environment. Strength has been increased at the expense of ductility owing to FSP in the current study. When exposed to SBF, however, the samples' surfaces degrade and create pits, leading to failure at relatively low stress and strain values. Once submerged, FSP ZM21 surpasses ZM21 in terms of strength. Significantly, after 24 hours in the water, ZM21's elongation percentage is lesser than that of FSP ZM21. We can deduce this from observations of surface morphology of submerged samples. Failure in ZM21 occurs at a lower elongation than in FSP ZM21 because of huge pits and significantly deteriorated surface regions.
Table 2 Mechanical properties from sample's stress-strain curves.
The development of FSP ZM21 demonstrates two significant successes: the ability to regulate degradation rate and protection of mechanical behaviour in a severe physiological environment. In current study's most notable findings include the smaller particle size, decreased intermetallic phase, and the production of supersaturated grains. FSP ZM21's hardness and strength are both improved due to these alterations. Furthermore, even after being exposed to the corrosive SBF medium, the mechanical response is affected by the improved biomineralization caused by grain refinement compared to ZM21. As a result, it is evident to comprehend how FSP's grain-refined ZM21 facilitates more significant mineralization with enhanced mechanical properties even after exposure to corrosive physiological environments, making FSP ZM21 an appropriate option for load-bearing orthopaedic degradable implant applications.
3.5. Corrosion characteristics
3.5.1 Immersion Test Degradation
In Fig. 11, the total weight loss of each sample over time is illustrated. In contrast to FSP ZM21 and the FSP ZM21-ß-TCP composite, the ZM21 surface exhibits a more rapid deterioration characterized by the formation of asymmetrical pits, while the FSP ZM21 ß-TCP sample provides enhanced resistance to chloride ion attack. Subsequently, the FSP ZM21 ß-TCP specimen underwent a coating process involving mineral phases including magnesium phosphate, HA, and others, in addition to the more stable Mg (OH)2 layer.
Ca2+ ions may be liberaed from the ZM21-ß-TCP composite with Mg2+ and OH− 1 ions as the composite degrades, resulting in a slightly higher pH than FSP ZM21. However, ZM21- ß-TCP composite surface degradation was homogeneous and weight loss was minimal compared to the other samples. It's possible that the enhanced bioactivity is responsible for this deterioration. The pH levels (Fig. 12), which were measured every 12 hours, demonstrate that ZM21 degraded at a faster pace, leading to an increase in pH.
The slower rate of disintegration in the composite after 24 hours indicates that the pH levels of both samples are nearly equal. A sample of FSP ZM21 ß -TCP always has a lower pH than a sample of ZM21.
3.5.2. Polarization test
It is evident from the OCP curves (Fig. 13(a)) that after 24 hours in SBF, both samples, i.e., FSP ZM21 and FSP ZM21 ß -TCP displayed stable potentials. However, both samples had variations in thermodynamic properties when corrosion began. As seen in Fig. 13(b), the pattern of sample corrosion potentials resembles that of polarisation curves. Table 3 lists the samples' corrosion currents (Icorr) and corrosion potentials (Ecorr). ZM21 samples had higher OCP than the FSP ZM21 ß -TCP sample, but the FSP ZM21 ß -TCP sample had a lower current density than the ZM21 sample, indicating that the FSP ZM21 ß -TCP samples are more corrosion resistant. The lower surface energy of the FSP ZM21 ß -TCP specimen, as well as the influence of grain size, can explain their increased corrosion resistance. There was a considerable decrease in FSP ZM21's corrosion rate based on its low current density. The inclusion of ß-TCP particles improved corrosion resistance, as shown by potentiodynamic polarisation findings.
|
Sample |
FSP ZM21 |
FSP ZM21(ß-TCP) |
|---|---|---|
|
Ecorr (V) |
-1.603 |
-1.780 |
|
Icorr (A/cm2) |
5.342 ×10− 3 |
4.116×10− 4 |
3.5.3 Electrochemical vs immersion corrosion test results
The corrosion rates of samples are given based on the weight loss after 72 hours of immersion and electrochemical testing, which results after 24 hours of immersion. Corrosion was shown to be more rapid on ZM21 in both studies. The ZM21-ß-TCP composite has lower corrosion rates than the FSP ZM21 sample in both immersion and electrochemical testing. Therefore, the corrosion rate of immersion test samples is significantly higher than that of electrochemical test samples. Different corrosion rates (AZ91D and LAE442) have been observed between immersion and electrochemical tests for Mg alloys. It was discovered that in vitro and in vivo corrosion rates are very different. Pure commercial Mg, AZ31, AZ80, and AZ91Mg alloys all show similar corrosion rate discrepancies based on the weight loss technique and electrochemical test.(30), along with evidence from electrochemical testing and studies of hydrogen evolution showing variations in corrosion rate. (31, 32). According to the authors (30), the unique electrochemical behavior of the metallic surface causes more than ten times as much corrosion in commercially pure Mg and AZ31 (two times as much as in other AZ series Mg alloys). The results of experiments conducted by Kirkland et al. (31) were discussed, as were the variations in corrosion rates between Mg-5Ca and Mg-10Zn magnesium alloys. The corrosion susceptibility of a specific material can be understood in many ways depending on the relative weight of its influence rather than its absolute magnitude (30, 31). Compared to the FSP ZM21 sample, the corrosion rate of the ZM21- ß-TCP composite is reduced. Due of their fine grain structure, FSP ZM21 and FSP ZM21- ß-TCP composites have a higher resistance to corrosion. The FSP ZM21-ß-TCP composite had the slowest corrosion rate of any of the test samples.
3.5.4. Corrosion morphology
As wrought and FSP ZM21 surfaces are shown in Fig. 15 before and after a brief immersion in the SBF, Large areas of Mg dendrites and many distributed intermetallic phases (Fig. 15(a)) have been recognized by many researchers as MgZn2 and Zn2Zr intermetallic compounds in the as-wrought ZM21 magnesium alloy (33). Figure 15(b) shows that early immersion corrosion was localized on grain boundaries and intermetallic phases. Dendrite's heterogeneous solute distribution and dendritic arms' non-equilibrium solidification zones led to uneven grain corrosion. Corrosion near intermetallic phases suggested they were nobler than the surrounding area, and electrochemical corrosion galvanic interaction quickened corrosion. During the FSP process, dendrites were broken into minute pieces and disseminated into heated softening materials, which were then absorbed into the SZ (Fig. 15(c)). Grain refinement, dendrite breakdown, and dissolving precipitated phases improve FSP ZM21 surface corrosion (Fig. 15(d)). XRD patterns immersed in SBF for 24 hours were analysed for corrosion resistance (Fig. 16). After long-term immersion in SBF, Mg OH)2 completely covered ZM21 magnesium alloy. The presence of Mg (OH)2 on the surface of ZM21 magnesium alloy suggests that the metal has been heavily corroded. Furthermore, the breakdown of Mg (OH)2 into OH ions is the principal source of the rapid increase in initial pH, which may cause alkaline poisoning in the tissues (33, 34). The lack of Mg (OH)2 in FSP-treated samples indicates that less magnesium has dissolved. The precipitation of Ca3(PO4)2 on ZM21-ß-TCP composite surfaces demonstrates that ß-TCP particles produce biomineralization on magnesium alloys. Ca3(PO4)2 can be replaced by autologous bone, which can mimic normal bone behaviour (34). According to the XRD data, the FSP samples with ß-TCP particles have higher corrosion resistance than the initial ZM21 magnesium alloy in SBF. They are also favourable to bone tissue production.
Figure 17 shows SEM pictures of samples immersed in SBF solution for 24 hours, demonstrating the shape and development of corrosion products. Elemental composition of EDS zones is shown in Table 4. The ZM21 sample's surface included some white deposits and a layer with numerous fissures (Fig. 17(a)). FSP ZM21 produced a denser, thicker precipitate layer than ZM21 (Fig. 17(c)). FSP ZM21 was coated in white flakes, as shown in Fig. 17(d).
Table 4 Corrosion products on the surface of samples submerged in SBF, as analyzed by EDS.
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The effect of FSP processing on the microstructure and mechanical characteristics of the Mg alloy ZM21 under the circumstances simulating the body's physiological conditions has been studied.
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An increase in hardness was seen for FSP ZM21-ß-TCP, and it was determined that this improvement was due to the smaller grain size. Tests of immersion in simulated bodily fluids showed increased apatite mineralization on FSP ZM21. Grain refinement from 107 ± 6.7 µm to 3.5 ± 1.5 µm was achieved after FSP.
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EDS studies indicated that ZM21-ß-TCP composites had a higher Ca/P ratio than FSP magnesium, which implies enhanced bioactivity. In addition, ZM21-ß-TCP composites with TCP particles biomineralize quicker than FSP magnesium.
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Surface morphology demonstrated a faster rate of degradation and creation of deep pits on ZM21 base alloy compared to FSP ZM21 after dissolving the corrosion products of immersed samples.
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Following immersion tests, FSP ZM21's tensile strength was higher than that of ZM21 due to grain refining.
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The findings revealed that the smaller grain size achieved in ZM21 using FSP improved mineral deposition, delaying deterioration. Furthermore, the improved mechanical behaviour of FSP ZM21 after exposure to corrosive environments provided an additional benefit for adapting FSP ZM21 Mg alloy as a suitable substitute for degradable orthopaedic implant applications.
Author Contribution
All authors reviewed the manuscript
- Li X, Liu X, Wu S, Yeung KWK, Zheng Y, Chu PK. Design of magnesium alloys with controllable degradation for biomedical implants: From bulk to surface. Acta Biomater [Internet]. 2016; 45:2–30. Available from: http://dx.doi.org/10.1016/j.actbio.2016.09.005
- Staiger MP, Pietak AM, Huadmai J, Dias G. Magnesium and its alloys as orthopedic biomaterials: A review. Biomaterials. 2006;27(9):1728–34.
- Witte F, Kaese V, Haferkamp H, Switzer E, Meyer-Lindenberg A, Wirth CJ, et al. In vivo corrosion of four magnesium alloys and the associated bone response. Biomaterials. 2005;26(17):3557–63.
- Wu G, Ibrahim JM, Chu PK. Surface design of biodegradable magnesium alloys - A review. Surf Coat Technol [Internet]. 2013; 233:2–12. Available from: http://dx.doi.org/10.1016/j.surfcoat.2012.10.009
- Matykina E, Garcia I, Arrabal R, Mohedano M, Mingo B, Sancho J, et al. Role of PEO coatings in long-term biodegradation of a Mg alloy. Appl Surf Sci [Internet]. 2016; 389:810–23. Available from: http://dx.doi.org/10.1016/j.apsusc.2016.08.005
- Wong HM, Yeung KWK, Lam KO, Tam V, Chu PK, Luk KDK, et al. A biodegradable polymer-based coating to control the performance of magnesium alloy orthopaedic implants. Biomaterials [Internet]. 2010;31(8):2084–96. Available from: http://dx.doi.org/10.1016/j.biomaterials.2009.11.111
- Yu H, Dong Q, Dou J, Pan Y, Chen C. Preparation of Si-containing oxide coating and biomimetic apatite induction on magnesium alloy. Appl Surf Sci [Internet]. 2016; 388:148–54. Available from: http://dx.doi.org/10.1016/j.apsusc.2016.02.051
- Jin W, Wu G, Feng H, Wang W, Zhang X, Chu PK. Improvement of corrosion resistance and biocompatibility of rare-earth WE43 magnesium alloy by neodymium self-ion implantation. Corros Sci [Internet]. 2015; 94:142–55. Available from: http://dx.doi.org/10.1016/j.corsci.2015.01.049
- Liu C, Liang J, Zhou J, Li Q, Wang L. Characterization of AZ31 magnesium alloy by duplex process combining laser surface melting and plasma electrolytic oxidation. Appl Surf Sci [Internet]. 2016; 382:47–55. Available from: http://dx.doi.org/10.1016/j.apsusc.2016.04.047
- Narvan M, Abdi Behnagh R, Shen N, Besharati Givi MK, Ding H. Shear compaction processing of SiC nanoparticles reinforced magnesium composites directly from magnesium chips. J Manuf Process [Internet]. 2016; 22:39–48. Available from: http://dx.doi.org/10.1016/j.jmapro.2016.01.010
- Ganesa Balamurugan K, Mahadevan K. Investigation on the changes effected by tool profile on mechanical and tribological properties of friction stir processed AZ31B magnesium alloy. J Manuf Process [Internet]. 2013;15(4):659–65. Available from: http://dx.doi.org/10.1016/j.jmapro.2013.04.001
- Zhao J, Liu Y, Sun W bin, Zhang H. Amorphous calcium phosphate and its application in dentistry. Chem Cent J. 2011;5(1):1–7.
- Tovar N, Jimbo R, Witek L, Anchieta R, Yoo D, Manne L, et al. The physicochemical characterization and in vivo response of micro/nanoporous bioactive ceramic particulate bone graft materials. Materials Science and Engineering C [Internet]. 2014; 43:472–80. Available from: http://dx.doi.org/10.1016/j.msec.2014.07.048
- Horch HH, Sader R, Pautke C, Neff A, Deppe H, Kolk A. Synthetic, pure-phase beta-tricalcium phosphate ceramic granules (Cerasorb®) for bone regeneration in the reconstructive surgery of the jaws. Int J Oral Maxillofac Surg. 2006;35(8):708–13.
- Samavedi S, Whittington AR, Goldstein AS. Calcium phosphate ceramics in bone tissue engineering: A review of properties and their influence on cell behavior. Acta Biomater [Internet]. 2013;9(9):8037–45. Available from: http://dx.doi.org/10.1016/j.actbio.2013.06.014
- The I, X-ray C, Caps T. General chemistry of the calcium orthophosphates. Studies in Inorganic Chemistry. 1994;18(C):1–62.
- Witte F, Feyerabend F, Maier P, Fischer J, Störmer M, Blawert C, et al. Biodegradable magnesium-hydroxyapatite metal matrix composites. Biomaterials. 2007;28(13):2163–74.
- ASTM E8. ASTM E8/E8M standard test methods for tension testing of metallic materials 1. Annual Book of ASTM Standards 4. 2010;(C):1–27.
- Razavi M, Fathi M, Savabi O, Tayebi L, Vashaee D. Biodegradable magnesium bone implants coated with a novel bioceramic nanocomposite. Materials. 2020;13(6):1–15.
- Kokubo T, Takadama H. How useful is SBF in predicting in vivo bone bioactivity? Biomaterials. 2006;27(15):2907–15.
- Huang G, Shen Y. The effects of processing environments on the microstructure and mechanical properties of the Ti/5083Al composites produced by friction stir processing. J Manuf Process [Internet]. 2017; 30:361–73. Available from: http://dx.doi.org/10.1016/j.jmapro.2017.10.007
- Kumar A, Pal K, Mula S. Simultaneous improvement of mechanical strength, ductility and corrosion resistance of stir cast Al7075-2% SiC micro- and nanocomposites by friction stir processing. J Manuf Process [Internet]. 2017; 30:1–13. Available from: http://dx.doi.org/10.1016/j.jmapro.2017.09.005
- Sharghi E, Farzadi A. Simulation of strain rate, material flow, and nugget shape during dissimilar friction stir welding of AA6061 aluminum alloy and Al-Mg2Si composite. J Alloys Compd [Internet]. 2018; 748:953–60. Available from: https://doi.org/10.1016/j.jallcom.2018.03.145
- Chen ZW, Cui S. On the forming mechanism of banded structures in aluminium alloy friction stir welds. Scr Mater. 2008;58(5):417–20.
- Tongne A, Jahazi M, Feulvarch E, Desrayaud C. Banded structures in friction stir welded Al alloys. J Mater Process Technol [Internet]. 2015; 221:269–78. Available from: http://dx.doi.org/10.1016/j.jmatprotec.2015.02.020
- Yang Q, Feng AH, Xiao BL, Ma ZY. Influence of texture on superplastic behavior of friction stir processed ZK60 magnesium alloy. Materials Science and Engineering A. 2012; 556:671–7.
- Fu BQ, Liu W, Li ZL. Calculation of the surface energy of hcp-metals with the empirical electron theory. Appl Surf Sci. 2009;255(23):9348–57.
- Huang Y, Wang Y, Meng X, Wan L, Cao J, Zhou L, et al. Dynamic recrystallization and mechanical properties of friction stir processed Mg-Zn-Y-Zr alloys. J Mater Process Technol [Internet]. 2017; 249:331–8. Available from: http://dx.doi.org/10.1016/j.jmatprotec.2017.06.021
- Decker RF, Berman TD, Miller VM, Jones JW, Pollock TM, LeBeau SE. Alloy Design and Processing Design of Magnesium Alloys Using 2nd Phases. Jom [Internet]. 2019;71(7):2219–26. Available from: https://doi.org/10.1007/s11837-019-03482-z
- Pardo A, Feliu S, Merino MC, Arrabal R, Matykina E. Electrochemical estimation of the corrosion rate of magnesium/aluminium alloys. International Journal of Corrosion. 2010; 2010:7–13.
- Kirkland NT, Birbilis N, Staiger MP. Assessing the corrosion of biodegradable magnesium implants: A critical review of current methodologies and their limitations. Acta Biomater [Internet]. 2012;8(3):925–36. Available from: http://dx.doi.org/10.1016/j.actbio.2011.11.014
- Liu X, Lim JY, Donahue HJ, Dhurjati R, Mastro AM, Vogler EA. Influence of substratum surface chemistry/energy and topography on the human fetal osteoblastic cell line hFOB 1.19: Phenotypic and genotypic responses observed in vitro. Biomaterials. 2007;28(31):4535–50.
- Karparvarfard SMH, Shaha SK, Behravesh SB, Jahed H, Williams BW. Microstructure, texture and mechanical behavior characterization of hot forged cast ZK60 magnesium alloy. J Mater Sci Technol [Internet]. 2017;33(9):907–18. Available from: http://dx.doi.org/10.1016/j.jmst.2017.04.004
- Pompa L, Rahman ZU, Munoz E, Haider W. Surface characterization and cytotoxicity response of biodegradable magnesium alloys. Materials Science and Engineering C [Internet]. 2015; 49:761–8. Available from: http://dx.doi.org/10.1016/j.msec.2015.01.017
No competing interests reported.