Stronger and coarser-grained biodegradable zinc alloys

Area of Science:

• Biomaterials Science
• Materials Engineering
• Orthopaedic Research

Background:

• Zinc (Zn) is a promising material for biodegradable implants due to its biocompatibility.
• The inherent softness of zinc limits its application in load-bearing orthopaedic devices.
• Reducing grain size in zinc increases strength but compromises mechanical stability and durability at body temperature.

Purpose of the Study:

• To develop stronger and more durable biodegradable zinc alloys for orthopaedic applications.
• To investigate the relationship between grain size, texture, and mechanical properties in dilute zinc alloys.

Main Methods:

• Extrusion of dilute zinc (Zn) alloys with controlled compositions.
• Microstructural analysis to determine grain size and texture.
• Mechanical testing to evaluate strength, durability, and deformation mechanisms.

Main Results:

• Extruded dilute Zn alloys achieved ultrahigh strength and excellent durability by increasing micron-scale grain size while maintaining basal texture.
• An inverse Hall-Petch effect was observed, with deformation shifting from grain boundary sliding to intra-granular pyramidal slip and unusual accommodation twinning.
• The achieved strength is nearly double that of current magnesium-based biodegradable alloys, making them the strongest and most stable to date.

Conclusions:

• Dilute zinc alloys with optimized grain size and basal texture exhibit superior mechanical properties for biodegradable implants.
• The identified deformation mechanisms, including accommodation twins, contribute to the enhanced strength and stability.
• These advanced zinc alloys represent a significant breakthrough for fabricating high-performance, load-bearing bone fixation implants.