Microstructure Evolution in Mg-Zn-Zr-Gd Biodegradable Alloy: The Decisive Bridge Between Extrusion Temperature and Performance

Abstract

Being a biocompatible metal with similar mechanical properties as bones, magnesium bears both biodegradability suitable for bone substitution and chemical reactivity detrimental in bio-ambiences. To benefit its biomaterial applications, we developed Mg-2.0Zn-0.5Zr-3.0Gd (wt%) alloy through hot extrusion and tailored its biodegradability by just varying the extrusion temperatures during alloy preparations. The as-cast alloy is composed of the α-Mg matrix, a network of the fish-bone shaped and ellipsoidal (Mg, Zn)3Gd phase, and a lamellar long period stacking ordered phase. Surface content of dynamically recrystallized (DRXed) and large deformed grains increases within 330–350°C of the extrusion temperature, and decreases within 350–370°C. Sample second phase contains the (Mg, Zn)3Gd nano-rods parallel to the extrusion direction, and Mg2Zn11 nanoprecipitation when temperature tuned above 350°C. Refining microstructures leads to different anticorrosive ability of the alloys as given by immersion and electrochemical corrosion tests in the simulated body fluids. The sample extruded at 350°C owns the best anticorrosive ability thanks to structural impacts where large DRXed portions and uniform nanosized grains reduce chemical potentials among composites, and passivate the extruded surfaces. Besides materials applications, the in vitro mechanism revealed here is hoped to inspire similar researches in biometal developments.

Analysis of defects in a twin roll cast Mg‐Y‐Zn magnesium alloy

“…This phase has been mentioned in previous studies, mainly for Mg-Gd-Zn alloys. [32][33][34][35] Based on the contents of Zn and RE, slight variations in chemical composition as well as lattice parameters may occur.…”

On the Corrosion Fatigue of Magnesium Alloys Aimed at Biomedical Applications: New Insights from the Influence of Testing Frequency and Surface Modification of the Alloy ZK60

“…Not only do Mg alloys exhibit excellent biocompatibility and natural biodegradability, they also exhibit low density (1.7-2.0 g/cm 3 ) and strength in excess of 250 MPa. Notably, the elastic moduli of Mg-based alloys (40)(41)(42)(43)(44)(45) are better compared to the stiffness of cortical bones (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) than those of conventional metallic materials used as permanent implants (c.f., ~200 GPa for stainless steel, ~230 GPa for cobalt-based alloys, and ~115 GPa for titanium alloys [10]), which helps to eliminate the stress-shielding effect hindering the healing process.…”

“…Among hundreds of Mg-based alloy compositions proposed for orthopaedic applications, tertiary Mg-Zn-X alloys are by far the most studied due to their outstanding properties profile, both in vitro and in vivo. Ca, Y, and Zr are by far the most popular additions to Mg-Zn systems when seeking a balanced combination of mechanical and biofunctional properties [11][12][13][14][15][16][17][18][19][20][21][22][23]. The commercial alloy ZK60 has been proven versatile enough for processing by various techniques, from conventional extrusion and rolling to a wide range of severe plastic deformation techniques, resulting in substantial microstructure refinement and the enhancement of tensile [24], fatigue [25] and corrosion properties [26][27][28].…”

The relationship between ignition and oxidation of molten magnesium alloys during the cooling process

“…Magnesium alloys are commonly recognized as one of the most potential materials in the aerospace industry and biomedicals ( Mehra et al, 2018 ; Yao et al, 2018 ; Cao et al, 2021 ). Casting is the main manufacturing process for magnesium alloy components.…”