时效态Al-5.5Cu-0.9Mg-0.2Sc-0.15Zr-1.0Ti合金的显微组织与拉伸性能

Microstructure and tensile properties of aged Al-5.5Cu-0.9Mg-0.2Sc-0.15Zr-1.0Ti alloy

通过进行光学显微镜、扫描电镜观察及拉伸性能测试,研究了时效态Al-5.5Cu-0.9Mg-0.2Sc-0.15Zr-1.0Ti合金的显微组织及不同温度下的拉伸性能。结果表明:Ti元素的添加,可以在合金晶粒内部产生Al3Ti相。随着时效时间的增加该合金室温抗拉强度和屈服强度均呈先增加后降低的趋势,并在时效8 h时达到最大值。断后伸长率随时效时间的增加呈现出下降的趋势。对T6态的Al-5.5Cu-0.9Mg-0.2Sc-0.15Zr-1.0Ti合金进行高温拉伸试验,其结果表明,随着试验温度的升高,合金的拉伸强度有所下降,而断后伸长率升高。利用SEM对合金的拉伸断口形貌进行观察,结果表明,在常温拉伸加载条件下,合金的拉伸断裂方式是以脆性为主的韧脆混合断裂;在高温拉伸加载条件下,合金断口处存在大量韧窝,断裂方式为韧性断裂。比较室温拉伸与高温拉伸的拉伸断口形貌可知,合金断裂方式由韧脆混合断裂转变为韧性断裂。

Microstructure and tensile properties at different temperatures of aged Al-5.5 Cu-0.9 Mg-0.2 Sc-0.15 Zr-1.0 Ti alloy were investigated by means of optical microscope,scanning electron microscopy and tensile test.The results show that the Al_3Ti phases are formed in the alloy grains by adding Ti element.The tensile strength and yield strength of the alloy at room temperature firstly increase then decrease with the increasing of the aging time,and reach the maximum values after aging for 8 h.The elongation of the alloy at room temperature decreases with the increasing of the aging time.The high temperature tensile tests are performed for the T6 state Al-5.5 Cu-0.9 Mg-0.2 Sc-0.15 Zr-1.0 Ti alloy.The results show that with the increasing of the testing temperature,the tensile strength of the alloy decreases slightly while the elongation increases.The SEM observation on the tensile fracture surfaces reveals that the tensile fracture mode of the alloy at room temperature is a mixed ductile-brittle fracture mode.At high temperature,a great amount of dimples appear on the fracture surface and a ductile fracture feature is noted.Comparing the morphology of tensile fracture surfaces at room and high temperatures,it can be seen that the tensile fracture mode changes from the ductile-brittle fracture to the ductile fracture.