The Prepatation, Microstructure And Properties Of Mg₂Si/AZ31 Alloys Prepared By Alloying AZ31 With Synthesized Mg-Si Binary Alloy

For Magnesium alloys, Mg2Si, with high hardness, high melting point, high elastic modulus, low density, low thermal expansion coefficient and other characteristics can improve high temperature performances of magnesium alloys as an ideal reinforcing phase. According to chemical reaction 4Mg+SiO2=Mg2Si+2MgO, Mg-Si binary alloys are designed and preparated with Mg and differents king of materials containing SiO2 as raw materials. Furthermore, Mg2Si/AZ31 is prepared by alloying AZ31 with synthesized bineray Mg-Si alloys by using conventional solidification. The use of optical microscopy (OM), energy dispersive analysis (EDS), X-ray diffraction (XRD), tensile test, hardness test methods for observation of microstructure and test performance. the following conclusions were obtained by analysising:1. With pure magnesium and highly purity quartz powder, quartz sand, soda-lime glass powder as raw materials, Mg-Si binary alloys were prepared. The microstructure of Mg-Si binary alloy consists of primary Mg2Si, (Mg2Si+α-Mg) eutectic andα-Mg phase in different proportions. At 760℃casting temperature the absorptivity of Mg-10%Si binary alloy prepared with highly pure quartz powder is 59.2%, the absorptivity of Mg-10%Si binary alloy prepared with silica sand is 47.2%, the absorptivity of Mg-10%Si binary alloy prepared with soda-lime glass is 28.3%.The more Si content of the raw materials, the easier to get high Si content of the Mg-Si binary alloy; finer granularity of the raw material, the easier to get high Si contents of the Mg-Si binary alloys.2. Sb alloy has obvious modifying effect on primary Mg2Si phase of the Mg2Si/AZ31 system. Primary Mg2Si will be transformed into eutectic Mg2Si entirely with adding 2% Sb.3. Si plays a significant role on the mechanical properties of alloy Mg2Si/AZ31, along with the Si contents of Mg2Si/AZ31 alloy increased, volume fraction of Mg2Si increased, the hardness of Mg2Si/AZ31 alloy increased, tensile strength and elongation decreased; Mg2Si particles is smaller, alloy tensile strength and elongation is better.