摘要
The effects of T6 heat treatment on thixoforged A356 and A380 aluminium alloys were studied.Low superheat casting(LSC)technique was carried out to prepare proper specimens for thixoforging process.The samples were poured at 20°C above their liquidus temperatures which provided the formation of equiaxed grains instead of dendritic growth.Produced billets were reheated for varied time from 20 to 80 min and thixoforged with 50%deformation rate.After thixoforging process,the samples were T6 heat treated for both A356 and A380 alloys.The microstructural evaluation and hardness alteration of thixoforged,solution treated and aged specimens were examined comparatively by using optical microscopy,scanning electron microscopy with energy-dispersive X-ray spectroscopy and Brinell hardness equipment.T6 heat treatment provided relatively uniform microstructure with newly formed precipitates that are Mg2Si and Al2Cu for A356 and A380 billets,respectively.Accordingly,hardness after artificial aging was increased considerably and reached HB 93 for A356 and HB 120 for A380 alloys.
研究T6热处理对触变锻造A356和A380铝合金的影响。采用低过热铸造(LSC)技术制备用于触变锻造的样品。为了获得等轴晶粒并防止枝晶生长,将样品在高于液相温度20°C时进行浇铸,将浇铸坯料再加热不同时间(20~80 min)后进行触变锻造,变形量为50%,再将触变锻造后的A356和A380铝合金样品进行T6热处理。用光学显微镜、能量弥散X射线谱仪、扫描电镜和布氏硬度仪对经触变锻造、固溶处理和时效处理后样品的显微组织和硬度变化进行检测。结果表明,T6热处理后合金的显微组织更均匀,并分别在A356和A380坯料中形成了新的析出相Mg_2Si和Al_2Cu。相应地,经过人工时效后,样品的硬度大幅度提高,A356铝合金的硬度达到HB 93,A380铝合金的硬度达到HB 120。
