Zinc And Deformation Process Of Gd - 3-6-0.5 - Zr Y Mg Alloy Microstructure, Texture And Mechanical Properties Of Impact

By using optical microscope(OM), universal tensile testing machine, X-ray diffraction(XRD), scanning electron microscope(SEM), high resolution transmission electron microscope(HRTEM) and electron backscatter diffraction(EBSD), the microstructures, texture and mechanical properties of the Mg-6Gd-3Y-0.5Zr alloys were investigated through alloying, hot extrusion, hot rolling and ageing. Experiment results are obtained as follows:1. Mg12Zn(YGd) phases can be found in Mg-6Gd-3Y-0.5Zr magnesium alloy with Zn addition. They are identified as the LPSO structures due to their long-period stacking order. Two LPSO structures with different images are found in the alloys:the block-shaped ones at grain boundaries and needle-like ones in the inner grains.6H’-type LPSO structures with ABCBCB’stacking sequence are determined in the homogenized specimen, where A and B’layers are significantly enriched by Gd、Y and Zn. The better tensile properties of the extruded and extruded-rolled Mg-6Gd-3Y-xZn-0.5Zr sheets than Mg-6Gd-3Y-0.5Zr one indicates that LPSO structures can improve the alloys’mechanical properties.2. The microstructures of the as-extruded alloys are refined through DRX(dynamic recrystallizition). The microstructures of the extruded-rolled alloys are elongated along the deformation direction, and the proof strengths and ultimate tensile strengths are improved obviously. The proof strength and ultimate tensile strength of extruded-rolled Mg-6Gd-3Y-1.4Zn-0.5Zr alloy reach318MPa,382MPa respectively, and the elongation reaches8%.3. The needle-like LPSO structures in the Mg-6Gd-3Y-xZn-0.5Zr alloys can inhibit the decomposition of the supersaturated solid solution and delay the ageing peak. Fortunately, the tensile mechanical properties of the T5and T10alloys are improved by the needle-like LPSO structures throuth distribute the precipitations dispersively and decrease the size. The proof strength and ultimate tensile strength of Mg-6Gd-3Y-1.4Zn-0.5Zr alloy in T10condition reach369MPa and425MPa respectively. 4. There are two texture components in the extruded Mg-6Gd-3Y-0.5Zr sheet:{0001} basal texture and a non-basal texture with basal poles splitting about±40°from normal direction towards transverse direction. For the hot extruded-hot rolled sheet, the non-basal texture components disappeared and{0001} basal texture enhanced.5. The schmid factors of {0001}<1120> basal plane slip system of the as-extruded sheet in0°、45°and90°directions show an increasing trend, and the proof strength and ultimate tensile strength in the three directions show an opposite trend. The schmid factors of {0001}<1120> basal plane slip system of the hot extruded-hot rolled sheet in0°、45°and90°directions are less than that of the as-extruded sheet, and the proof strengths and tensile strengths are higher than that of the as-extruded sheet, and it shows obvious texture strengthening effect.