AA7136铝合金挤压板材浸入式末端淬火温度场实验与有限元模拟研究

Experiment and finite element simulation of submerged end quenching temperature field of AA7136 aluminum alloy extruded plate

提出浸入式末端淬火新方法。以AA7136铝合金挤压板材为对象,通过实验和有限元模拟研究淬火温度场,建立硬度和强度与淬火速率的关系曲线,结合微观组织表征分析淬火敏感性机理。研究结果表明:在浸入式末端淬火过程中,界面换热系数随表面温度降低先升高后降低,在表面温度为206℃时达到峰值(30.5 kW·m^(-2)·℃;);实测的时间-温度曲线与有限元模拟曲线基本一致;随着试样浸入水中深度从25 mm增至100 mm,最大淬火速率从410℃·s^(-1)增加至425℃·s^(-1);随着淬火速率降低,硬度在淬火速率大于90℃·s^(-1)时基本不变,在15~90℃·s^(-1)范围内缓慢下降,在小于15℃·s^(-1)后迅速下降;强度在淬火速率大于15℃·s^(-1)时缓慢下降,之后迅速下降,约4℃·s^(-1)后变化不大;淬火析出η相的形成是引起硬度和强度下降的主要原因。

A new method of submerged end quenching was proposed for AA7136 alloy extruded plate. The quenching temperature field of AA7136 alloy extruded plate was investigated by experiment and finite element simulation. The relationship between hardness, strength and quenching rate was established, and the quenching sensitivity mechanism was analyzed combined with microstructure characterization. The results show that the interfacial heat transfer coefficient increases firstly and then decreases with the decrease of surface temperature,and the peak value(30.5 kW·m^(-2)·℃;) appears at the surface temperature of 206 ℃. The measured time-temperature curve is basically consistent with simulation curve. The maximum quenching rate increases from410 ℃ ·s^(-1)to 425 ℃ ·s^(-1)with the increase of immersion depth from 25 mm to 100 mm. With the decrease of quenching rate, the hardness changes slightly when the quenching rate is higher than 90 ℃·s^(-1), decreases slowly in the range of 15-90 ℃ ·s^(-1), and decreases rapidly when the quenching rate is less than 15 ℃ ·s^(-1). The strength decreases slowly when the quenching rate is higher than 15 ℃·s^(-1), and then decreases rapidly, and finally changes slightly when the quenching rate is lower than 4 ℃ ·s^(-1). The formation of quench-induced η phase is the main reason for the decrease of hardness and strength.