Fabrication And Deformation Behavior Of In-situ Particulate Reinforced Magnesium Matrix Composites

More attention has been paid to magnesium alloys which have been applied in aerospace, automobile, transportation and consumer industries, where weight saving is of great importance. However, the low strength has limited the wide application of magnesium alloys. Magnesium containing high content of RE element exhibits excellent mechanical properties, but has a high manufacturing cost which is adverse for universal application. Therefore, the lower rare earth content and maintaining a certain performance become one of the key development directions in Mg-RE alloys. In addition, material workers have not carried out the research about Mg-RE matrix composite. Accordingly, with the combination of high strength magnesium and composte technique, the effects of in-situ particles on the microstructure and properties of Mg-Gd-Y-Zn and Mg-Gd-Y-Zn-Zr matrix composites were studied, and the effect of hot extrusion and T5 aging treatment on the composites were also investigated; Moreover, the microstructure, mechanical properties and deformation mechanism of as-extruded TiB2/AZ31 composite were also studied.The main research results are as follows:1. Multiple in-situ particles reinforcing Mg-Gd-Y-Zn and Mg-Gd-Y-Zn-Zr matrix composites were prepared by high temperature self-propagating synthesis-semisolid srir casting technique. In-situ TiB2 and Al2(Y, Gd) particles can effectively refine the microstructure of as-cast Mg-Gd-Y-Zn alloy, and the morphology of a-Mg transform coarse fir-tree crystal into fine equiaxed grains. The mechanical properties increase to some extent. Whereas, the microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloy decreases due to the consumption of Zr element;2. After hot extrusion, in-situ particles in Mg-Gd-Y-Zn matrix composite array along to the extrusion direction, and dynamic recrystallization grains are found around reinforced particles. The mechanical properties of composite greatly increase after hot extrusion. Especially, the tensile strength and elongation of 2 wt.% Al-Ti-B/Mg-Gd-Y-Zn composite reach up to 330 MPa and 13.3%, respectively, increasing 16.6% and 38.5% compared with as-extruded matrix alloy, and increasing 67.5% and 52.4% compared with as-cast 2 wt.% AI-Ti-B/Mg-Gd-Y-Zn composite; 3. The 200℃/50h artificial aging treatment is carried on the as-extruded Mg-Gd-Y-Zn matrix composite. This aging system has little influence on the microstructure of as-extruded composite, and the strength of the composite increases within a narrow range. Especially, the tensile strength of 2 wt.% Al-Ti-B/Mg-Gd-Y-Zn composite are 342 MPa. Otherwise, the elongation of 6 wt.% Al-Ti-B/Mg-Gd-Y-Zn composite greatly increases to 15.2% after aging treatment, increasing 56.7% and 360.6% compared with as-extruded and as-cast 6wt.% Al-Ti-B/Mg-Gd-Y-Zn composite;4. Hot extrusion can effectively refine the microstructure of TiB2/AZ31 magnesium matrix composite, and improve the homogeneous distribution of TiB2 particles. During the hot extrusion of TiB2/AZ31 composite, slip and twinning are the main deformation mechanism. The deformation depends not only on the respective operation of slip and twinning, but also the joint between slip and twinning.