Biodegradable Mg-Zn-Y alloys with long-period stacking ordered structure: optimization for mechanical properties

Area of Science:

• Materials Science
• Biomaterials Engineering
• Metallurgy

Background:

• Biodegradable orthopedic implants require optimized mechanical properties for successful clinical application.
• Magnesium alloys containing long period stacking ordered (LPSO) phase are being investigated for their potential as orthopedic materials.
• Understanding the relationship between microstructure and tensile properties is crucial for alloy development.

Purpose of the Study:

• To investigate the microstructures and tensile properties of Mg-Zn-Y alloys with LPSO phase.
• To optimize these alloys for enhanced mechanical performance suitable for biodegradable orthopedic implants.
• To explore the effects of alloying elements (Zn, Y, Ca, Zr) and processing (warm extrusion) on alloy properties.

Main Methods:

• Synthesis and characterization of as-cast Mg-Zn-Y alloys with varying Zn and Y content (Mg(100-3x)(Zn(1)Y(2))(x), 1 ≤ x ≤ 3).
• Investigation of the effect of calcium (Ca) substitution for yttrium (Y) on phase formation.
• Micro-alloying with zirconium (Zr) for grain refinement and evaluation of warm extrusion processing.

Main Results:

• The volume fraction of the 18R LPSO phase increased with higher Zn and Y content, with Mg(97)Zn(1)Y(2) showing the best strength-plasticity combination.
• Calcium substitution favored Mg(2)Ca phase formation over LPSO phase. Zirconium addition refined α-Mg grains to 30 μm, improving both strength and plasticity.
• Warm-extruded alloys exhibited significantly enhanced strength and plasticity due to dynamic recrystallization and LPSO phase alignment.

Conclusions:

• Mg-Zn-Y alloys with LPSO phase can be tailored for improved mechanical properties.
• Zirconium micro-alloying and warm extrusion are effective strategies to enhance strength and plasticity for orthopedic applications.
• Optimized Mg-Zn-Y-Zr alloys present a promising candidate for biodegradable orthopedic implants.