焊接过程中Al-Mg-Zn铝合金的微观组织变化

7系Al-Mg-Zn铝合金是广泛应用于高速列车车体的结构材料,本研究的材料为轧制后经过固溶处理并经自然时效的热处理强化板材。列车的焊接制造过程中,由于焊接热源作用改变型材的热处理状态,导致接头区域的力学性能弱化。通过采集焊接试验过程中的热循环曲线,研究7系铝合金焊接接头热影响区的温度变化过程,并根据热循环特征对T4热处理状态的铝合金板材进行热模拟试验,划分热影响区的固溶区和过时效区,并分析热影响区的组织演变和硬度分布规律。结果表明,采用脉冲MIG和激光-MIG复合焊两种焊接方法,在接头的固溶区域均出现软化,但经过100天的自然时效,强度可恢复到母材水平。

Microstructure evolution of Al-Mg-Zn alloy during welding procedure

7XXX Al-Mg-Zn alloy was a widely used structure material in high-speed train body production manufacturing.In this paper,the aluminum alloy was heat treated by solution treatment along with natural aging process.During the welding process,the heattreated condition of aluminum alloy would be transformed by the welding heat source,resulting in the weakening of the mechanical properties of weldment.In this paper,the thermal cycling curve was collected during welding procedure test.Subsequently,the temperature evolution in HAZ was analyzed,and HAZ was subdivided into two sections of solid-solution area and aging area by peak temperature.Furthermore,the microstructure evolution and hardness distribution of two kinds of HAZ was concluded.After pulsed-MIG welding and laser-MIG hybrid welding procedure tests,hardness softening was recovered after 100 days natural aging process.