振动时效对7075铝合金薄壁构件应力松弛的影响与分析

Effects of vibratory stress relief on stress relaxation of 7075 Al alloy thin-walled components

对铝合金薄壁构件进行振动时效(VSR)实验研究,观察时效对材料表面的影响。通过X-ray表面应力测试、硬度测试和TEM电镜实验,对材料表面特性中的应力分布、相区状况、位错和显微硬度进行了分析,实验结果表明:VSR可使构件加工表面微屈服而造成应力松弛,在30 min、60 min的时效时间里,表面应力幅度分别下降了22%和32%。同时,发现相区内晶粒得到细化,且不同状态下晶界处的位错密度也明显不同,这说明振动交变应力造成了构件表面材料的微观形变,进而阐述了应力松弛的机理和材料显微硬度增长的原因。分析认为VSR对薄壁构件既消减了表面应力峰值,又强化了表面硬度,这对提高材料表面的抗变形能力有利。

The vibration stress relief(VSR)tests were conducted for 7075 Al alloy thin-walled components to observe VSR effects on material surface.Through surface stress measuring with X-ray diffraction(XRD),hardness tests and TEM ones,material surface features including stress distribution,phase domain state,dislocation and micro-hardness were analyzed.The test results showed that VSR can make component machined surface micro-yield and have stress relaxation,the surface stress amplitude decreases 22%and 32%,respectively in 30 min and 60 min;crystal particles are refined in phase domain and the dislocation density at grain boundary under different states is obviously different,it means the vibration alternating stress produced due to VSR makes component surface material have micro-strain,and then the mechanism of stress relaxation and the reason for increase in material micro-hardness are presented;VSR not only reduces thin-walled component surface material’s stress peak value,but also enhances the surface material hardness,this is beneficial to improve the anti-deformation ability of component surface material.