区熔式定向凝固技术对7075铝合金微观组织和硬度的影响研究

Effect of Zone Melting Directional Solidification Technology on Microstructure and Hardness of 7075 Aluminum Alloy

采用Bridgman定向凝固系统对7075铝合金进行区熔式定向凝固试验,研究了感应加热温度(887~998℃)、拉伸速率(20~50μm/s)对凝固组织及硬度的影响。结果表明,7075铝合金定向凝固后,组织由原始枝晶形貌转变为等轴或近等轴柱状晶;当感应加热温度998℃且拉伸速率40μm/s时,得到的柱状晶形貌稳定,尺寸均匀,硬度最高。在参数范围内拟合的感应加热温度与试样硬度的线性关系式为HB=0.055T+15.5(T为温度)。

The zone melting directional solidification test of 7075 aluminum alloy was carried out by using Bridgman directional solidification system. The effects of induction heating temperature(887-998)℃ and tensile rate(20-50 μm/s) on solidification microstructure and hardness were studied. The results show that the microstructure of 7075 aluminum alloy changes from primary dendrite to equiaxed or nearly equiaxed columnar crystal after directional solidification. When the induction heating temperature is 998 ℃ and the tensile rate is 40 μm/s, the columnar crystal has stable morphology, uniform size and the highest hardness. The linear relationship between the temperature of induction heating and the hardness of the sample was fitted in the range of parameters. The linear relation between the induction heating temperature and the hardness of the sample is HB=0.055 T+15.5(T is the temperature).