淬火冷却速率对6082铝合金力学性能的影响

Effect of Quench Rate on Mechanical Properties and Microstructure of 6082 Al-alloy

采用末端淬火(JEQ)实验、使用JMatpro7.0模拟软件并结合硬度、拉伸性能测试以及透射电子显微镜(TEM)观测,研究了轨道交通用6082铝合金的淬火敏感性。结果表明:(1)由JMatpro7.0模拟得到的TTT曲线表明,6082铝合金的淬火敏感温度区间为220~425℃,β和β’’相的鼻尖温度为375℃。合金的CCT曲线表明,为了抑制淬火过程中β’(亚稳相)的析出,合金的淬火冷却速率必须大于6℃/s;(2)随着末端淬火距离D的增大6082铝合金的时效态硬度和强度下降,淬透深度为23 mm;(3)随着淬火冷却速率的降低淬火诱导析出相β在异质形核点α-(AlMnFeSi)相上优先析出,在后续的时效过程中β相长大并吸收周围的溶质原子,晶内时效析出强化相β’’减少;(4)慢冷过程中,晶界附近的空位浓度降低,晶界的无沉淀析出带(PFZ)变宽。

The quenching sensitivity of 6082 Al-alloy used in rail transit was investigated systematically by means of Jominy end-quench(JEQ) test, JMatpro7.0 simulation software, hardness test, tensile test and TEM. Results show that(1) The quenching sensitive temperature range is between 220~425℃.The nasal tip temperature for β’-and β’’-phase is 375℃. According to the CCT curve, in order to suppress the precipitation of metastable β’-phase the cooling rate should be greater than 6℃/s during quenching process;(2) The hardness and strength decreased with the increase of the distance from the quenched end, and the depth of aging hardening layer is about 23 mm;(3) the quench-induced β-precipitates preferentially precipitated and grown on the heterogeneous nucleation site of α-(AlMnFeSi) phase, with the decrease of quenching cooling rate. During the subsequent aging process, the β-phase grows and absorbs the surrounding solute atoms, the strengthening precipitated β’’-phase is reduced;(4) During the slow cooling process, the vacancy concentration near the grain boundaries decreases, and the precipitationfree precipitation zone(PFZ) at the grain boundaries widens.