时效制度对2A97铝锂合金组织和力学性能的影响Effect of aging treatment on microstructure and mechanical properties of 2A97 Al-Li alloy

采用硬度测试、拉伸性能测试、DSC分析和透射电镜(TEM)等方法研究不同时效制度对2A97铝锂合金组织和性能的影响。结果表明：采用165 ℃人工时效时，峰值强度最高，但其塑性也最差，且达到峰值的时间长达60 h；200 ℃人工时效时，达到峰值的时间缩短为6 h，而其峰值强度和塑性均很差；(200 ℃, 6 h)+(165 ℃, 6 h)双级时效优化后，可获得比200 ℃峰时效更高的强度，其抗拉强度为545 MPa，只比165 ℃峰时效强度低11 MPa，伸长率却提高至7.1%，且时效时间比165 ℃峰时效时缩短了48 h。2A97铝锂合金峰时效状态下的析出相有T₁(Al₂CuLi)相、θ′相和一定量的σ(Al₅Cu₆Mg₂)相。根据不同升温速率下的DSC曲线，采用Kissinger法求得T₁相的析出激活能为75.9 kJ/mol。综合分析可知，采用(200 ℃, 6 h)+(165 ℃, 6 h)双级时效可以得到比单级时效更加优异的综合性能。

The effect of aging treatment on the microstructure and mechanical properties of 2A97 Al-Li alloy during artificial aging was studied by hardness measurement, tensile test, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results indicate that 2A97 alloy obtains the highest strength, but its elongation is relatively low when aged at 165 ℃ for 60 h; when it is aged at 200 ℃, only 6 h is needed to achieve peak aging, whereas the peak strength and elongation are both poor; when the alloy is aged at (200 ℃, 6 h)+(165 ℃, 6 h), the aging time of which is 48 h less than that of single aging treatment when peak values are obtained, while the tensile strength is 545 MPa, only 11 MPa less than that of single aging treatment, and the elongation increases to 7.1%. The T₁(Al₂CuLi) phase, θ'''' phase and σ(Al₅Cu₆Mg₂) phase are the major precipitates in 2A97 alloy. According to the DSC curves at various heating rates, the activation energies of T₁ phases by Kissinger method is 75.9 kJ/mol. To sum up, the (200 ℃, 6 h)+(165 ℃, 6 h) double aging treatment can endow the alloy with more excellent comprehensive performance than single aging system.

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