(1. 浙江大学 宁波理工学院，宁波 315100；2. 北京有色金属研究总院，北京 100022)
摘 要: 采用椭圆旋扭管反复凝熔法制备半固态A356铝合金浆料。结果表明：椭圆旋钮管反复凝熔技术具有旋扭强制对流促进初生晶核游离、自搅拌加强熔体剪切、反复凝熔促进形核的作用，可使初生α晶核演变为球形或近球形晶粒。椭圆管长短轴比、旋扭强度以及凝熔频率对半固态浆料的微观组织有显著影响。随着长短轴比、旋扭强度和凝熔频率的增大，晶粒细化和圆整效果显著提高；但长短轴比过大，容易堵塞流道；当旋扭强度超过13.5 (°)/cm时，晶粒细化和圆整效果没有明显提高；当凝熔频率超过40 μm−1时，晶粒细化作用不再增强，圆整度反而降低。在椭圆长短轴比为1.8׃1、旋扭强度为13.5 (°)/cm、凝熔频率为40 μm−1的条件下可制得晶粒直径细小、形状圆整的半固态浆料。
关键字: A356铝合金；椭圆旋钮管；反复凝熔法；半固态；微观组织
repeated heating-cooling method with elliptical-twisted tubes
（1. Ningbo Institute of Technology, Zhejiang University, Ningbo 315100, China;
2. Beijing General Research Institute for Nonferrous Metals, Beijing 100088, China）
Abstract:The semi-solid slurry of A356 aluminum alloy was prepared by the repeated heating-cooling method with the elliptical-twisted tubes. The results indicate that by the repeated heating-cooling method with elliptical-twisted tubes the microstructures of primary grains are transformed from dendritic or rosette-shaped to fine net-globular under the action of grains detachment due to the forced convection, shear caused by self-stirring and heterogeneous nucleation because of repeated heating/cooling. The axial ratio, twisting strength and heating-cooling frequency have significant influences on the microstructure of the semi-solid slurry. With the increase of axial ratio, twisting strength and heating-cooling frequency, the grain refinement and sphericity of particles have remarkable improvement. However, at the twisting strength over 13.5 (°)/cm and heating-cooling frequency over 40 μm−1, the grain refinement does not have a much improvement and the sphericity decreases on the contrary. At the axial ratio of 1.8:1, twisting strength of 13.5 (°)/cm and heating-cooling frequency of 40 μm−1, the favorable microstructure of semi-solid A356 aluminum alloy can be generated by the repeated heating-cooling method with the elliptical-twisted tubes.
Key words: A356 Al alloy; elliptical-twisted tube; repeated heating-cooling method; semi-solid; microstructure
