时效对铜铝钎焊接头界面化合物和性能的影响

采用Zn-22Al钎料对铜铝异种合金进行了火焰钎焊,并用加速老化试验模拟了其服役环境.研究了时效过程中铜铝钎焊接头界面化合物的形貌变化及其对铜铝钎焊接头电阻率和抗剪强度的影响,并对其生长规律进行了初步计算.结果表明,铜侧界面化合物在250℃恒温时效过程中不断变厚,其生长规律呈抛物线状,且其生长系数约为6.1×10-13cm2/s;当界面化合物的厚度为4.2μm和18.1μm时,铜铝接头的电阻分别为120.3μΩ和132.9μΩ,该界面化合物厚度对电阻率的影响系数为0.25;铜铝接头抗剪强度在时效过程中先有3%的上升,随后逐渐降低至接头初始值的85%.

Effects of thermal aging on intermetallic compounds and properties of Cu/Al brazing joint

Cu/Al dissimilar metals were joined with Zn-22Al filler metal by torch-brazing technology and heat treated at constant temperature of 250 ℃ for 0 to 1000 h.To guarantee the reliability of the Cu/Al torch-brazing joints in service requirement,the growth rate of intermetallic compounds on Cu side was calculated and the effects of the intermetallic compound layer on the electrical and mechanical properties have been investigated under various annealing time.It was observed that the width of intermetallic compound increased as the thermal aging proceeded,and the growth rate of the intermetallic compound was 6.1×1013 cm2/s when the aging temperature was 250 ℃.A thicker intermetallic compound layers could degrade the resistivity and shear strength of Cu/Al joints.When the thickness of intermetallic compound was 4.2 μm and 18.1 μm,the electric resistance was 120.3 μΩ and 132.9 μΩ,respectively.Moreover,the shear strength of Cu/Al brazing joint increased by 3% when the aging time was 100 h while the strength decreased by 15% when the Cu/Al joints endured 1000 h thermal aging.