TC18钛合金动态力学行为及变形失效机理研究

The dynamic mechanical behavior, deformation and failure mechanism of titanium alloy have attracted much attention of worldwide researchers. In this program, a metastable near-beta titanium alloy, TC18 will be studied. Various initial microstructures are obtained throuth hot processing and heat treatment. Dynamic compression test and shear test will be performed using Hopkinson bar to study the dynamic mechanical properties and deformation-failure process of titanium alloys with different microstructures. The evolution of microstructure before and after loading will be characterized using SEM (Scanning Electron Microscope) and TEM (Transmission Electron Microscope). Special attention will be paid to the microstrucrtures of the zones in and near adiabatic shear bands. The sensitivity of adiabatic shear bands will be evaluated for titanium alloy with various initial microstructures. The deformation-failure process and its mechanisms will also be investigated through multiscale numerical simulation. The aim of this research is to establish the relationship between microstructure and dynamic mechanical properties for titanium alloy. This research is helpful for understanding the dynamic behavior and deformation and failure mechanism of titanium alloy. It has guidance meaning for the selection, design and failure analysis of metal materials such as titanium alloys used for high-strain-rate situations.

钛合金的动态力学行为及变形失效机理是国内外研究人员重点关注的一个研究课题。项目以亚稳态近β型TC18高强韧钛合金为研究对象，通过热加工和热处理获得不同的显微组织。利用Hopkinson压杆进行高应变率加载，开展动态压缩和动态剪切实验，对不同组织钛合金的动态力学性能及变形失效过程进行观测。利用扫描电镜和透射电镜等对材料加载前后的组织演化进行表征，重点分析绝热剪切变形区及周围组织结构的变化，评价不同组织钛合金的绝热剪切敏感性。对钛合金动态变形失效过程进行宏细观多尺度模拟，分析钛合金动态变形失效机理，找到钛合金组织结构与其动态力学性能及变形失效之间的关系。本项目的研究有助于加深对钛合金的动态力学行为及变形失效机理的认识，对高应变率工况下钛合金等金属材料的失效分析和材料选择、设计等都具有积极的指导意义。

钛合金具有高比强度、耐高温和耐强腐蚀性等优点，在航空航天、船舶和兵器工业等领域颇具应用价值。本课题基于分离式霍普金森压杆加载手段，结合超高速数字图像相关技术、多点高速红外测温系统和应变“冻结”技术，系统探讨TC18钛合金的温度、应变和应变率敏感性和组织结构对TC18钛合金力学行为的影响。研究表明，钛合金的动态力学行为与应变率、加载温度和微观组织结构相关，在一定加载条件下发生动态失效，其断裂模式为剪切破坏。位错是钛合金发生塑性变形的主要原因，材料内部的位错密度越高，对应的剪切应变越大，而维氏硬度越低。钛合金的动态变形过程分为“均匀变形”、“非均匀变形”和“应变高度局域化”三个阶段。其中，“应变高度局域化”是钛合金发生应力“坍塌”的主要原因。钛合金在一定加载条件下形成ASB，其宽度随着名义剪切应变的增加而增大直至达到饱和，ASB的形成并不意味相变的发生。基于有ASB诱导形成的裂纹扩展路径可知“界面脱粘”可作为TC18钛合金的动态失效机理。研究成果深化了对TC18钛合金动态力学行为及失效机理的认识，对于推广钛合金在涉及爆炸与冲击等高应变率领域的应用具有重要的参考价值。