论文部分内容阅读
采用常规铸造和喷射成形工艺制备了含硅达25%(质量分数)的过共晶Al-Si合金,利用SEM(EDS)、XRD和DSC等分析方法对合金的显微组织和相熔解析出进行了分析研究.结果表明,铸态合金含有粗大块状初晶Si相和粗大针片状含铁相,而喷射成形工艺能够使二者的尺寸、形貌发生改变而有利于合金性能的提高.同时,铸态和沉积态合金中均含有基体Al、初晶Si和Al2Cu相,不同的是铸态合金中含铁相主要为δ-Al4FeSi2相,而沉积态合金中以β-Al5FeSi相为主.分析其原因主要是糊状层的存在引起沉积坯冷却速度降低而导致沉积坯中发生δ-Al4FeSi2相的转变及共晶组织增加,致使沉积态合金中β-Al5FeSi相为主要含铁相.采用DSC实验对沉积态合金在熔化和凝固过程中发生的反应进行了讨论.
Hypereutectic Al-Si alloys containing 25% (mass fraction) silicon were prepared by conventional casting and injection molding techniques. The microstructure and phase composition of the alloy were analyzed by SEM (EDS), XRD and DSC The results show that the as-cast alloy contains rough bulk Si phase and coarse needle-like iron-containing phase, while the injection molding process can change the size and morphology of the as-cast alloy and improve the performance of the alloy At the same time, both as-cast and as-deposited alloys contain matrix Al, primary Si and Al2Cu phases, except that the iron-containing phase in the as-cast alloy is mainly δ-Al4FeSi2 phase, whereas the as-deposited alloy has β-Al5FeSi phase as The main reason is that the existence of mushy layer leads to the decrease of the cooling rate of the billet, resulting in the transformation of δ-Al4FeSi2 phase and the increase of the eutectic structure in the billet, which leads to the β-Al5FeSi phase in the as-deposited alloy as the main iron phase The reactions that occur during melting and solidification of the as-deposited alloys are discussed using DSC experiments.