冷热循环对铝合金锥形件淬火残余应力和加工变形的影响

Influence of Thermal-cooling Cycle on Both Quenching-induced Residual Stress and Machining-induced Distortion of Aluminum Cone-shaped Part

为消除锥形件残余应力、提高工件尺寸精度,基于数值模拟和试验分析,研究冷热循环处理工艺对淬火残余应力、加工变形的影响。结果表明:冷热循环后工件残余应力分布趋势与T6态基本一致,呈'外压内拉'分布,但残余应力幅度大为降低;工件经T6处理加工后大端口部圆度变化量在0.06～0.10mm,经冷热循环后工件尺寸稳定性提高,圆度变化量基本在0.04mm以内。建立'应力、应变波动模型',分析残余应力、应变的微观热力行为及波动机制;建立冷热循环对残余应力、应变影响的表征模型,并结合TEM组织分析,指出冷热循环过程中组织结构不均匀热胀冷缩效应,引发不均匀微塑性变形,促使可动位错耗竭和固定位错缠结、增殖,从而释放内部残余应力、抑制加工变形,宏观表现为工件尺寸稳定性提高。

In order to release residual stress and improve dimensional precision of aluminum cone-shaped part,the influence of thermal-cooling cycle on both quenching-induced residual stress and machining-induced distortion,based on numerical modeling and test analysis,is studied.The experimental results show that the distributing trend,which is compressive stress on the surface and is tension stress on the interior,of residual stresses with thermal-cooling cycle is similar to that with T6 treatment,but the amplitude of residual stress treated by thermal-cooling cycle is reduced sharply,and that the fluctuation quantity of roundness is 0.06～0.10 mm with T6 treatment,and is controlled generally within 0.04 mm with thermal-cooling cycle,the dimensional stability is improved obviously after thermal-cooling cycle.The characterization model of both quenching-induced residual stress and strain is established,the microcosmic thermodynamic behavior and fluctuating mechanism of both residual stresses and strain is analyzed.The characterization model of influence of thermal-cooling cycle on both residual stress and strain is established,the reason of releasing residual stress and improving dimensional stability with thermal-cooling cycle is that the asymmetric thermal expansion and contraction of microscopic structure is produced,the asymmetric thermal microplastic deformation is induced,and the movable dislocation is consumed and the pinned dislocation tangle and dislocation multiplication is excitated on the basis of TEM microscopic structure analysis.