汽车车身用Al-Mg-Si-Cu-Mn合金板材强度与n值的相关性研究

Study on the correlation between strength and n value of Al-Mg-Si-Cu-Mn alloy sheet for automobile body

提出了一种实用的根据Al-0.67Mg-1.35Si-0.64Cu-0.61Mn合金板材强度预测应变强化指数n值的方法以评价铝板的拉深性能。通过热处理调控板材中析出相粒子均为运动位错以切割方式通过的细小的AlMgSiCu团簇的前提下,获得屈服强度R_(p0.2)和抗拉强度R_(m)。分别为88 N/mm^(2)~199 N/mm^(2)和235 N/mm^(2)~335 N/mm^(2)的合金板材,利用单向拉伸试验研究了铝板的R_(p0.2)和R_(m)与应变强化指数n值之间的关系,并建立了n值的预测模型以评价合金板材的冲压成形性能。结果表明,对于溶质原子以位错能切割通过的溶质原子团簇形式从基体中析出的Al-0.67Mg-1.35Si-0.64Cu-0.61Mn合金板材,其n值随强度的增大而降低,当其在0.03~0.20应变范围内拉伸变形时,其对应于不同计算终点应变的应变强化指数n_(c)。(c对应于不同计算终点应变量)与计算终点应变ε、R_(p0.2)和R_(m)分别满足n_(c)=0.4513-0.1778e^(-ε/4.521)-0.0011R_(p0.2)和n_(c)=0.6690-0.1773e^(-ε/4.647)-0.0013R_(m)。当铝合金板的R_(p0.2)和R_(m)分别小于100 N/mm^(2)和240 N/mm^(2)时,板材的n_(15)值分别大于0.33和0.35。若板材的R_(p0.2)或R_(m)分别升高100 N/mm^(2),其n_(c)将分别下降0.11或0.13。

A practical method for predicting the work-hardening exponent n value based on the strength of Al-0.67Mg-1.35Si-0.64Cu-0.61Mn alloy sheet to evaluate the deep-drawing performance is put forward.The alloy sheets of yield strength R_(p0.2)88 N/mm^(2)-199 N/mm^(2)and tensile strength R_(m)235 N/mm^(2)-335 N/mm^(2)were obtained,respectively through different heat treatments making the precipitates in alloy sheets small-sized AlMgSiCu clusters which can be cut by moving dislocations during plastic deformation.The relationship between the work-hardening exponent n value and the R_(p0.2)and R_(m)of Al-0.67Mg-1.35Si-0.64Cu-0.61 Mn alloy sheet was investigated by uniaxial tensile test,and the prediction model of n value was established to evaluate the stamping formability of alloy sheet.Results show that the n value decreases with the increased strength when the solute atoms are precipitated in the form of ultrafine clusters which can be cut by dislocation energy in Al-0.67Mg-1.35Si-0.64Cu-0.61Mn alloy sheet.Within the studied tensile strain rangeε(0.03-0.20),the stain-hardening exponent n_(c)。corresponding to different target strains(where c is corresponding to target strain),target strainε,yield strength R_(p0.2),and tensile strength R_(m)were developed in the following equations,respectively.That is n_(c)=0.4513-0.1778e^(-ε/4.521)-0.0011R_(p0.2)and n_(c)=0.6690-0.1773e^(-ε/4.647)-0.0013R_(m).The n_(15)values are greater than 0.33 and 0.35 correspondingly when R_(p0.2)and R_(m)of alloy sheet are less than 100 N/mm^(2)and 240 N/mm^(2),respectively.The n_(c)valves are dropped by 0.11 or 0.13 if R_(p0.2)or R_(m)of alloy sheet are increased by 100 N/mm^(2),respectively.