2A97铝锂合金双级时效研究

Study on Double-Aging of 2A97 Aluminum-Lithium Alloy

通过TEM分析和常规力学性能测试,研究双级时效工艺对2A97铝锂合金组织和性能的影响,以优化合金强度和塑性匹配。结果表明:随预时效温度升高,双级时效基体由形成θ′/θ″相和δ′相为主的组织转变为形成T1相、θ″/θ′和δ′相为主的组织。135℃预时效、双级时效基体形成大量细小的θ′/θ″相和δ′相,T1数量少。晶界和亚晶界T1数量多,尺寸小,晶界和亚晶界θ′/θ″无析出带宽度窄。155℃预时效、双级时效可在基体形成以T1相为主的组织,且数量多,尺寸大,均匀分布,T1相、θ″/θ′和δ′相的联合强化作用使合金具有高的强度。

To optimize the relationship of strength and ductility of an aluminum-lithium alloY,2A97,a double-aging treatment was employed.The effect of double-aging processes on microstructures and tensile properties was investigated by transmission electron microscopy（TEM） and tensile tests.Results show that with the pre-aging temperature increasing,the formation of the strengthening precipitates T1 is promoted at the matrix at 155℃,instead of the precipitation of θ″/θ＇ and δ＇ phases at 135℃.It is different from that T1 precipitates nucleate and grow mainly at grain and subgrain boundaries at 135℃.Numerous fine θ″/θ＇ precipitates at the marx at 135℃ cause the reduction of the width of θ″/θ＇ precipitates-free zones adjacent to grain and subgrain boundaries and the size of equilibrium precipitates T1 at grain and subgrain boundaries.Numerous larger precipitates T1 dispersing homogeneously at matrix,combined with numerous large size θ＇ and δ＇ precipitates,yield higher tensile strength for the microstructure of double aging with 155℃ pre-aging than that of double aging with 135℃ pre-aging.