Forced convection rheoforming process for preparation of 7075 aluminum alloy semisolid slurry and its numerical simulation

A self-developed forced convection rheoforming （FCR） machine for the preparation of light alloy semisolid slurry was introduced. The microstructure characteristics of 7075 aluminium alloy semisolid slurry at different stirring speeds prepared by the FCR process were analyzed. The experimental results suggest that with the increase of the stirring speed, the mean grain size of the semisolid decreases and the shape factor as well as the number of primary grains increase. Meanwhile, the preparation process of semisolid slurry was numerically simulated. The flow characteristics of the melt in the device and the effect of the stirring speed on temperature field and solid fraction of the melt were investigated. The simulated results show that during the preparation process of semisolid slurry, there is a complex convection within the FCR device that obviously changes the temperature field distribution and solid fraction of the melt. When the convection intensity increases, the scope of the undercooling gradient of the melt is reduced and temperature distribution is improved.

强制对流搅拌制备铝合金半固态浆料及其组织演变

采用自主研发的强制对流搅拌装置（FCR），研究筒体温度、浇注温度和搅拌速度对A356铝合金半固态组织的影响规律，探讨半固态浆料制备过程中的凝固行为。结果表明：适当降低浇注温度、筒体温度和提高搅拌速度均有利于半固态浆料组织的改善，能够制备晶粒细小、圆整、分布均匀的半固态组织；当浇注温度为620~630℃、筒体温度为570~580℃、筒体转速为200 r/min以上时，均能获得理想的半固态浆料，其初生固相颗粒平均直径在80μm以下，形状因子在0.75以上；强制对流搅拌装置极大地改变了传统凝固条件下熔体依靠传导单向传热和扩散缓慢传质的状态，使熔体的温度场和成分场趋于一致，破坏了枝晶生长的条件，有利于获得较好的半固态组织。

强制搅拌方法制备A356铝合金半固态浆料

介绍了自主研发的强制搅拌流变成形设备(FCR),其核心部件是剪切搅拌机构和电气温度控制系统。研究了不同浇注温度对A356铝合金半固态组织的影响规律。结果表明,该试验设备在转速为200r/min,搅拌时间为30s,浇注温度为620℃时,可制备出晶粒细小(80μm)、形貌圆整(圆整度为0.75)且分布均匀的半固态组织。随着浇注温度的降低,合金初生相明显细化,形貌更加圆整,组织更加均匀。