高温升率下LY12铝合金拉伸破坏及其机理的研究

使用Gleeble1500热力模拟实验系统研究了温升率及其历史对LY12铝合金拉伸破坏的影响。对采用不同温升率加热到给定温度后的试件的拉伸试验表明，相同工作温度下经历较高温升率历史的试件的强度较低；以不同温升率对不同预载应力水平的试件快速加热直至破坏，发现预载应力相同时经历较高温升率试件的失效温度较低．对试件断口附近材料金相组织的分析表明，当工作温度或预载应力水平相同时，较高温升率下材料的微缺陷明显增加．高温升率造成的局部热失配及材料微观组织结构的损伤，不同温度、应力和时间下材料的再结晶程度等对材料的宏观本构行为及失效具有重要影响．

INVESTIGATION TO THE TENSILE FAILURE OF LY12 SUBJECTED TO THERMOMECHANICAL LOADING WITH HIGH HEATING-RATE

Using a Gleeeble 1500 thermal mechanical material testing system, experiments are performed to investigate the effect of heating rate and its history on the tensile strength of LY12 aluminum alloy at different working temperatures, and to determine the failure temperature of the material for the given preloaded stresses. Metallographical analysis of the fracture region shows that besides temperature and preloaded stress level, heating rate plays a significant role. The local thermal inconsistency is introduced and verified with a numerical example. It shows that high heating rate may induce very strong local residual stress that may cause severe damage in the material. Since most engineering materials are, in nature, heterogeneous, the study on the effect of high heating rate on the materials properties will be of great significance.