Wu Chengcheng, Lin Fengxiang, Liu Hong, Pelletier Matthew H, Lloyd Max, Walsh Williams R, Nie Jian-Feng
Department of Materials Science and Engineering, Monash University, Clayton, Victoria, Australia.
Department of Physics and Engineering Sciences, Karlstad University, Karlstad, Sweden.
Nature. 2025 Feb;638(8051):684-689. doi: 10.1038/s41586-024-08415-8. Epub 2025 Feb 12.
Zinc is emerging as a key material for next-generation biodegradable implants. However, its inherent softness limits its use in load-bearing orthopaedic implants. Although reducing the grain size of zinc can make it stronger, it also destabilizes its mechanical properties and thus makes it less durable at body temperature. Here we show that extruded Zn alloys of dilute compositions can achieve ultrahigh strength and excellent durability when their micron-scale grain size is increased while maintaining a basal texture. In this inverse Hall-Petch effect, the dominant deformation mode changes from inter-granular grain boundary sliding and dynamic recrystallization at the original grain size to intra-granular pyramidal slip and unusual twinning at the increased grain size. The role of the anomalous twins, termed 'accommodation twins' in this work, is to accommodate the altered grain shape in the plane lying perpendicular to the external loading direction, in contrast to the well-known 'mechanical twins' whose role is to deliver plasticity along the external loading direction. The strength level achieved in these dilute zinc alloys is nearly double those of biodegradable implants made of magnesium alloys-making them the strongest and most stable biodegradable alloys available, to our knowledge, for fabricating bone fixation implants.
锌正成为下一代可生物降解植入物的关键材料。然而，其固有的柔软性限制了它在承重骨科植入物中的应用。虽然减小锌的晶粒尺寸可以使其更强，但这也会使其机械性能不稳定，从而使其在体温下的耐久性降低。在此，我们表明，当稀释成分的挤压锌合金在保持基面织构的同时增加其微米级晶粒尺寸时，可以实现超高强度和优异的耐久性。在这种反霍尔-佩奇效应中，主导变形模式从原始晶粒尺寸下的晶间晶界滑动和动态再结晶转变为增大晶粒尺寸下的晶内锥面滑移和异常孪晶。在这项工作中，这些异常孪晶被称为“协调孪晶”，其作用是在垂直于外部加载方向的平面内适应改变的晶粒形状，这与著名的“机械孪晶”不同，后者的作用是沿外部加载方向提供塑性。据我们所知，这些稀释锌合金所达到的强度水平几乎是镁合金制成的可生物降解植入物的两倍，使其成为用于制造骨固定植入物的最强且最稳定的可生物降解合金。
