基于多场耦合医用钛合金α相快速再结晶及取向调控研究

Because of the crystal defect, texture and microstress in the fine-grained titanium alloy for medical implants from the plastic deformation, the damage and fracture caused by the poor toughness in the titanium equipment have attracted more and more attention of biological material industry at home and abroad. Compared with the conventional heat treatment, the rapid crystallization and the orientation controlling of the α phase can be controlled by the coupling effect of stress and electric and temperature field. The understanding of the relevant mechanisms should be taken into consideration deeply. In this project, biomedical Ti-6Al-4V wire (α phase size: 1～5um, β phase size: 0.5～1um ) is prepared by the warm working. The influence mechanisms of the multi-field coupling on the vacancies diffusion and dislocation movement and rapid crystallization are investigated. Furthermore, the intensity reduction extent of slip-induced equiaxed α phase (0001) texture and the orientation type of stress-induced secondary α phase are determined. In addition, the quantitative relationship between the cooling shrinkage stress of the α phase and the constant stress applied in the coupling is explored. This project not only enhance the understanding of the rapid fine-grained mechanism and the dynamics, but also promote the basic research of α phase orientation selection. It is of significant to optimize preparation technology of medical fine-grain titanium alloy.

医用细晶钛合金的韧性较差易导致其制备的器械损伤断裂引起国内外生物材料界的关注，主要因为变形合金中存在大量晶体缺陷、微观应力和织构。同传统热处理相比，应力-电流-温度耦合处理具有快速实现再结晶和调控相取向的特点，相关机理的认识还不深入。本项目拟以变形医用细晶（α相尺寸为1～5μm，β相尺寸为0.5～1μm）Ti-6Al-4V钛合金线材为研究对象，通过研究合金的多场耦合处理，阐明空位扩散和位错运动对等轴α相快速细晶化的影响机理，确定晶界滑移致等轴α相(0001)取向密度减小程度和应力诱发次生α相取向类型；结合钛合金α相晶格间距变化，探索合金冷却收缩应力与外加恒应力的定量关系。本项目不仅会加深对快速细晶化机理和动力学的理解，而且对促进我国钛合金相取向选择的基础研究发展、优化细医用晶钛合金制备工艺都具有重要意义。

该项目按照计划对钛合金α相快速再结晶及取向开展研究。该项目进展顺利， 阐明了多场耦合作用下α相快速再结晶的机理，完成了预期目标。在针对α相快速再结晶及取向机理的研究方面，我们选取了大变形量轧制棒材作为研究对象，较好地分析了微米级α相尺寸分布和晶体取向演变，揭示了热效应及非热效应对α亚晶长大的作用机理（2018 Journal of Materials Science）；处理前后组织和残余应力对比分析揭示了电-热-力耦合对合金晶粒细化及残余应力演变的影响（2018 Vacuum）。多场耦合处理后的细晶钛合金具有高强度、高塑性、高屈强差和低残余应力的优异性能。满足了国内外医疗行业对骨植入钛合金微螺钉性能提高的需求。获得了低能耗和高效率的短流程处理条件下钛合金组织-性能调控的创新机制，也将促进其在工业生产中进一步广泛应用。