镁/铝双金属复合管气压胀形-冷缩结合工艺研究

Investigation on Gas Blow Forming-Cold Contraction Bonding Technology of Mg/Al

摘要:

本文提出了双金属复合管的气压胀形-冷缩结合成形新工艺。首先通过热拉伸试验确定了AZ31镁合金和7475铝合金两种挤压管在420、440和460℃的周向流动应力和延伸率,在此基础上,计算出了使铝管和镁管产生变形所需的初始气压和最大气压,并且在460℃实现了AZ31/7475双金属复合管的成形,所成形的AZ31/7475双金属复合管结合紧密,无冶金结合；研究了因铝管、镁管和模腔之间存在偏心而导致的复合管横截面壁厚不均匀分布规律；推导出了管间残余接触应力的计算公式,其包含卸载气压后因弹性恢复不同引起的残余接触应力和因两种合金冷缩量不同引起的残余接触应力,利用压缩实验实测了复合管的残余接触压力,理论计算值与实测值吻合较好,相差约19.2%。

Abstract:

A new gas blow forming-cold contraction bonding process for forming Mg/Al composite tube was presented .The circumferential flow stress and elongation of AZ31 magnesium alloy and 7475 aluminum alloy were obtained by the unidirectional hot tensile tests at 420℃, 440℃and 460℃. On the basis of these datas, the initial gas pressure and maximum gas pressure required to deform the Al tube and Mg tube was calculated and the AZ31/7475 composite tube was successfully manufactured at 460℃. The as-formed AZ31/7475 composite tube is closely combined with no metallurgical bonding. Due to the existence of eccentricity between the AZ31/7475 tubes and the die cavity, the wall thickness distribution of the cross section is not uniform; The residual contact stress between outer tube and inner tube was deduced, which includes the residual contact stress caused by the elastic recovery and the residual contact stress caused by the cold shrinkage of the two alloys. The residual contact stress of the composite tube was measured by the compression tests and the calculated value agrees well with the measured value, with a difference of about 19.2%.