A356铝合金低过热度浇注的铸造显微组织研究

Research on Casting Microstructure of A356 Aluminum Alloy by Low Superheat Pouring

采用低过热度浇注技术制备半固态A356铝合金,研究了冷却强度、保温时间、浇注温度对铸造显微组织的影响.研究结果表明,在液相线附近,冷却强度大,晶粒细小;随着保温时间的延长,晶粒变大,形状变得圆整,结晶组织均匀;浇注温度越高,晶粒越粗大;铸锭中心部位组织比边缘部位组织粗大,且均匀,球化明显.低过热度浇注可以获得理想的A356铝合金半固态浆料.半固态坯料重熔加热温度为585℃,保温30min,α-Al相逐渐变成球状,此时,晶粒平均等级圆直径为42.6μm,晶粒平均圆度为2.13.

The semi-solid of A356 aluminum alloy is manufactured by low superheat pouring. The effects of cooling rates, holding time and pouring temperature on casting mierostructure of the alloy manufactured are investigated. The results indicate that the size and the shape of grain of A356 become large and spherical with the increase of cooling intensity. The grains are bigger, more spherical and more uniform with prolonging preservation time. The grains become large with the increase of casting temperature. The grains in the centre of the ingot are larger, more spherical and more uniform than that in the edge. The fine semi-solid slurries of A356 alloy can be obtained by low superheat pouring. The semi-solid slurries are in 585℃ for remelting temperature and 30 min for heat preservation time. The α-Al evolves into spheroidal shape. Under these conditions, its average equal-area-circle grain diameter is 42.6μm and the average is 2.13.