深冷处理对固溶时效后2A14铝合金残余应力及尺寸稳定性的影响

Effect of Cryogenic Treatment on Residual Stress and Dimensional Stability of 2A14 Aluminium Alloy after Solid Solution and Aging

对2A14铝合金依次进行(380±5)℃×120 min退火、498℃×2 h固溶、160℃×6 h时效以及不同温度(-70,-90,-110,-130℃)保温6 h深冷+160℃×3 h时效处理,研究了深冷处理对试样内部残余应力、物相组成、微观结构、尺寸稳定性和力学性能的影响。结果表明:不同热处理后试样中心纵截面残余应力均呈内拉外压形式,深冷处理对残余拉应力的释放效果和对应力分布均匀化效果随深冷温度降低均先增后减,-90℃下深冷处理应力释放和均匀化效果最好;-130~90℃深冷处理可以细化晶粒、增加析出相数量、减小析出相尺寸、降低位错密度、提高析出相和位错分布弥散性;-130℃~70℃深冷处理可以提高2A14铝合金的尺寸稳定性、抗拉强度和屈服强度,但会降低断后伸长率。

2A14 aluminum alloy was treated by annealing of(380±5)℃×120 min,solid solution of 498℃×2 h,aging of 160℃×6 h,cryogenic under different temperatures(−70,−90,−110,−130℃)for 6 h and aging of 160℃×3 h in sequence.The effect of cryogenic treatment on residual stress,phase composition,microstructure,dimensional stability and mechanical properties of the samples was investigated.The results show that the residual stress on the longitudinal section at center of the samples after different heat treatments was in the form of internal tension and external pressure.The release and stress distribution homogenization effects of cryogenic treatment increased first and then decreased with the decrease of temperature.The stress release and homogenization effects by cryogenic treatment at−90℃were the best.The cryogenic at−130—−90℃could refine the grains,increase the number of precipitates,reduce the size of precipitates and the dislocation density,and increase the dispersion of precipitates and dislocations.Cryogenic treatment at−130—−70℃could improve dimensional stability,tensile strength and yield strength of 2A14 aluminium alloy,but reduced the percentage elongation after fracture.