初生相形态对半固态挤压铸造Al-Si-Mg-Fe合金力学性能的影响

Effects of Primary Phase Morphology on Mechanical Properties of Al-Si-Mg-Fe Alloy in Semi-Solid Squeeze Casting Process

采用气泡搅拌制备铸造铝硅镁合金半固态浆料(GISS)工艺,可以开发出具有细小均匀的球状晶体结构的半固态浆料。本文以轮毂铸件为例,研究通过带气孔的石墨头释放出细小惰性气体气泡,气泡在熔体内部引起强烈对流,使得热量可以迅速散失从而加快冷却速度;同时也使得熔体中的温度场更加均匀,抑制枝晶形成,得到细小的球状晶粒。通过改变吹气量、吹气时间以及石墨头表面积,即可获得不同固相率的浆料,最后采用挤压铸造工艺生产出合格铸件。结果表明,初生α(Al)的形状和粒径大小对铸件的拉伸强度和伸长率有很大的影响。

The gas induced semi-solid （GISS） process was developed to create Al-Si-Mg-Fe alloy semi-solid slurry with fine and uniform globular structure. With wheel hub castings as an example, the combination of local rapid heat extraction and vigorous agitation by the injection of fine inert gas bubbles through a graphite diffuser in molten metal held at a temperature above its liquidus temperature changes the morphology of primary α（Al） from coarse dendritic to rosette-like and finally to fine globular structure. The different solid fractions slurry was prepared by setting blowing capacity, blowing time and graphite diffuser head surface area. The GISS process produced semi-solid slurry at low solid fractions and then formed the slurry by a squeezing casting process to produce casting parts. The effects of primary phase morphology on the mechanical properties of Al-Si-Mg-Fe alloy were investigated. The results show that the ultimate tensile strength and elongation are affected by the shape factor and particle size of the primaryα（Al）.