The Microstructures and Properties of Al-11%Si-0.2~0.3%Mg Alloys and SiC particulates Reinforced Al-11%Si-0.3%Mg Composites

• Main Authors: Chiou, Chwei-Horng, 邱垂泓
• Other Authors: Yang Chiu-Fu
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/67837863427942127752

碩士 === 大同工學院 === 材料工程學系 === 84 === The first half of this work concerns a study on the feasibility of introducing non-heat-treatable high silicon aluminum alloy wheel materials to domestic aluminum alloy wheel foundries. The Al-11% Si alloys containing 0.2 ∼0.3% Mg were selected as candidates in this study and subjected to a series of in-lab evaluations and production-line trials. The results showed that the Al-11% Si-0.2∼0.3% Mg Alloy specimens can be best modified through an ad- dition of 0.03% Sr which gave rise to a modification rating of class 4∼5. A water quench procedure of the castings right after their removal from mould was found beneficial to the mechanical properties. In comparison with the Sr- modified specimens, the Al-11% Si-0.2∼0.3% Mg alloys modified by 0.16∼0.32% Sb exhibit poor modification rating with aspect ratios of eutectic silicon rating from 14:1∼6:1. Analysis of trial-cast Sr-modified high-silicon Al alloy wheels shows satisfactory microstructural characteristics with tensile strength , elongation and quality index of 184 MPa, 4.8% and 286MPa, respectivety, which were similar to those obtained from imported commerical non-heat- treatable high- silicon aluminum alloy wheels. The second half of this aims to investigate the effects of wetting pro- moters Ca and Mg and the modifier Sr on the Al-11% Si-0.3% Mg/SiCp composites. The microstructures of the composite and the interphases at reinforcing par- ticles/Al alloy matrix interfaces of the composites were investigated by OM, SEM/EDAX and XRD. Mechanical properties of the composites were examined by tensile tests and bending test. The results showed that the bonding strength of SiC particulate to the aluminum alloy matrix can be greatly enhanced by the wetting prometer Ca and that the modifier Sr helps to produce desirable silicon morphology in aluminum alloy matrix for improved properties.