晶粒组织对2195铝锂合金应力时效析出行为与性能的影响

Effect of Grain Microstructure on Precipitation Behavior and Properties of 2195 Al-Li Alloy Under Stress-Aging

通过恒应力蠕变拉伸、室温拉伸及慢应变速率拉伸应力腐蚀性能测试等试验,结合OM、SEM、TEM及EBSD等组织观察,分析探究变形和细晶2种不同晶粒组织对应力时效处理2195铝锂合金析出行为与性能的影响。结果表明:与细晶组织板材相比,变形组织板材达到峰值硬度的时间由18h缩短至4h,峰值硬度(HV)由1619.94MPa升高到2234.4 MPa,抗拉强度由584.6 MPa提升至641.9 MPa。通过计算细晶强化、位错强化及析出相强化对合金强度提高的贡献值,发现变形组织板材力学性能提升主要来源于位错强化的贡献。同时,与细晶组织板材相比,变形组织板材的应力腐蚀敏感指数ISSRT值由7.6%降低到4.8%,应力腐蚀敏感性降低。变形组织板材的大角度晶界比例由细晶组织板材的64.6%降低至41.1%,晶界析出相分布更为离散,几乎观察不到无沉淀析出带,是获得较为优异抗应力腐蚀性能的主要原因。

The effects of two different grain structures i.e.deformation and fine-grain microstructure,on precipitation behavior and properties of 2195 Al-Li alloy were analyzed by constant stress creep tensile test,room temperature tensile test and slow strain rate tensile stress corrosion test combined with OM,SEM,TEM and EBSD.The results show that compared with the fine-grained sheet,the time for the deformed sheet to reach the peak hardness is shortened from 18 h to 4 h,the peak hardness increases from 1619.94 MPa to 2234.4 MPa,and the tensile strength increases from 584.6 MPa to 641.9 MPa.By calculating the contribution values of grain refinement strengthening,dislocation strengthening and precipitation strengthening to the improvement of alloy strength,it is found that the improvement of mechanical properties of deformed sheet is mainly due to the contribution of dislocation strengthening.At the same time,compared with the fine-grained sheet,the ISSRT value of the deformed sheet reduces from 7.6%to 4.8%,and the stress corrosion susceptibility reduces.The proportion of large-angle grain boundaries of the deformed sheet reduces from 64.6%to 41.1%of the fine-grained sheet,the grain boundary precipitation phase distribution is more discrete,and the precipitation-free zone is hardly observed,which is the main reason for obtaining relatively excellent stress corrosion resistance.