淬火水温对铝合金残余应力影响规律的超声表征

Ultrasonic Evaluation of Effect of Temperature of Quenching Water on Residual Stress of Aluminum Alloy

绘制了预拉伸态和40~70℃水淬火并冷压时效的7050铝合金试样沿厚度、轧制、宽展三个方向传播的超声速度分布图和底损图,并分别计算其声速极差。结果表明:沿三个方向传播的超声波的声速分布图与试样中的残余应力场均存在相关关系,其中沿厚度方向传播的超声声速分布图不受材料厚度方向组织差异的影响,可作为分析试样整体残余应力场的手段;沿轧制和宽展方向传播的超声声速分布图受到组织和应力的双重影响,但仍可通过声速等高线的弯曲程度分析试样中的残余应力;随淬火水温升高,声速分布图的均匀性增加,声速极差减小,符合残余应力形成的规律;50℃水淬火试样的声速分布图的特殊性是由其淬火方式的特殊性造成的。试验结果初步证实了利用超声方法表征铝合金试样整体残余应力的可行性。

Profile of velocity and amplitude of bottom reflection of ultrasonic propagated along three directions of 7050 pre-stretched aluminum alloy and that was quenched in water with temperature from 40℃to 70℃and then cold compressed and aged was drawn.Results show that velocity profiles of ultrasonic propagated along three directions were related to residual stress field in specimen.Velocity profiles of ultrasonic propagated along thickness direction was unaffected by microstructure.The velocity profile was available for analysis of residual stress field in specimen.Velocity profiles of ultrasonic propagated along rolling and broading direction were affected by microstructure and residual stress together.Degree of crook of contour of velocity was useful for analysis of residual stress as well.When temperature of quenching water increases,homogeneity of velocity profile increases and range of velocity decreases.This is fitting for regularity of thermal residual stress.Feature of velocity profile of the specimen quenched in water with temperature of 50℃may shows its particularity of quenching.The feasibility of integral residual stress evaluated by ultrasonic was proved by the experimental results preliminarily.