介质冷却散热搅拌半固态技术制备铝合金的组织及温度场模拟

Microstructure and Temperature Field Simulation of Aluminum Alloy Prepared by Semi-solid State Stirring Technology with Medium Cooling

基于机械搅拌制备半固态浆料原理,将冷却介质通入搅拌轴改变其散热条件开发出介质冷却散热搅拌半固态技术。对不同冷却介质散热搅拌下的铝合金熔体凝固温度场和凝固组织进行数值模拟和试验研究。结果表明,搅拌使熔体能够与搅拌轴对流换热,使其温度场均匀地降至过冷温度区间,促进形核,破坏了枝晶生长的环境,得到近球状组织;叠加介质冷却增加搅拌轴散热,形成熔体-搅拌轴-介质连续换热结构,大幅减少熔体降至过冷温度区间的时间,更快地达到更大的过冷度,进一步促进形核,细化晶粒;同时制浆结束后搅拌轴在介质冷却条件下可以快速降至室温,通过每次制浆初始条件的稳定保证了半固态浆料制备的稳定性,非常适合于流变压铸的快节奏批量化生产。

Based on the principle of preparing semi-solid slurry by mechanical stirring,the technology of medium cooling and cooling stirring semi-solid was developed by passing the cooling medium into the stirring shaft to change the heat dissipation condition.The solidification temperature field and solidification microstructure of the aluminum alloy melt under the heat dissipation and stirring of different cooling media were numerically simulated and experimentally studied.The results show that stirring can convect heat transfer between melt and stirring shaft,so that the temperature field drops evenly to the subcooled temperature range,promotes nucleation,destroys the dendrite growth environment,and obtains nearly spherical structure.Superimposed medium cooling increases the heat dissipation of stirring shaft,forming a melt-stirring shaft-medium continuous heat exchange structure,greatly reducing the time of melt falling to the subcooling temperature range,faster to achieve bigger subcooling,further promoting nucleation,refining grains.At the same time,the stirring shaft can be rapidly reduced to room temperature under the condition of medium cooling after the pulping,and the stability of semi-solid slurry preparation can be ensured by the stability of the initial conditions of each pulping,which is very suitable for the fast rhythm mass production of rheological die casting.