Microstructure Evolvement And Mechanics Behavior Of High Silicon Aluminum Alloys Prepared By Spray Deposition

Exsiting of coarse silicon and iron-rich phases in high-silicon aluminum alloys obstacles their applications in automobile engine, compressor and air conditioner, where weight saving, low thermal expansion and high wear-resistance are required. Rapid solidification offers an effective way for improving mechanical properties by refining silicon and iron-rich phases and promoting non-equilibrium phases to form. High-silicon containing aluminum alloys were prepared by spray deposition and their microstructures, thermodeformation process and heat treatment process were investigated in this study.Compared with conventional cast alloys, Al-Si-Cu-Mg-Fe alloys prepared by spray deposition had finer micostructure. It was found that in the deposition processing the semisolid droplet was broken into small liquid particle and crashed into the deposition surface, resulting in fine equiaxed microstructure formed in the billet.The effect of spray pressure on microstruture in Al-Si-Cu-Mg-Fe alloys prepared by spray deposition was inveatigated. The results indicated that increasing of pressure leads to fine primary silicon phases forming. The size of silicon grains was significantly increased with increasing silicon content, even at higher atomization pressure.Hot extrusion causes the diminishment of porosity in the Al-25Si-4.5Cu-1.5Mg-4.5Fe alloys prepared by spray deposition. No fiber structure was found in the extruded direction. The sourdness material was fabraicted at the 16:1 of extrusion proportion. The primary silicon had a little increase at the extrusion proporation of 8:1 and changed to fine distribution when the extrusion proportion was increased to 16:1. The needle-shaped phases were diminished on the alloys produced by two extrusion proportions.The growth of secondary phases and solution of some small phases occurred during solution trestment of extruded Al-25Si-4.5Cu-1.5Mg-4.5Fe alloys. With the increasing of solution time, the coarsing and smoothing of secondary phases were appeared. There was no marked increase in the grain size of secondary phases after aging treatment, while some fine phase precipitated. The highest HV...