Influence Of Solidification Conditions And Heat-treatment On Microstructure And Properties Of Mg-10gd-3y-0.4zr Alloy

In magnesium alloys,Gd,Y rare earth elements can form dispersed and thermally stable phase, which can effectively impede dislocation motion,so Mg-Gd-Y alloys as an important heat-resistant alloy system,have broad prospects in the aerospace,transportation, and electronics and other fields. In this paper, Mg-10Gd-3Y-0.4Zr alloy as the research object, studied by thermal analysis, optical microscopy, X-ray diffraction analysis, Vickers hardness, tensile test analysis, scanning electron microscopy and other means, systematic analysis of the influence of solidification conditions and heat treatment process for the alloy microstructure evolution,mechanical properties and fracture behavior at room temperature and high temperature.In this paper we use resin sand molding and gravity casting method to preparation of test samples. Different solidification conditions control by cold iron placement and control pouring temperature, are 750℃ casting no cold iron, 720℃ casting no cold iron, 720℃ casting with cold iron.Results show that no matter what kind of solidification conditions of tissue obtained are α-Mg + eutectic phase, while at low temperatures and cold iron casting solidification, eutectic was divorced eutectic state. Effects of different conditions on the cast solidified organization is reflected in the size of the grain size and eutectic phase, morphology and distribution. Under the condition of as-cast grain size and size of eutectic phase is 750℃ casting no cold iron >720℃ casting no cold iron > 720℃ casting with cold iron,but eutectic phase dispersion law was contrary. In the subsequent heat treatment, since the initial organization of genetic effects, the grain size and dispersion of the second phase resulting coincides with the cast. The mechanical properties under the same conditions of coagulated tissue from as-cast to T4 to peak-age is incrementally and the microstructure involves followed byThe solidification conditions peak point of sample of aging:high temperature casting, 505℃×12h+215℃×27h;low temperature casting no cold iron, 485℃×14h+215℃×23h; low temperature casting with cold iron, 465℃×12h+215℃×21h.At room temperature,150℃ and 250℃ condition,mechanical properties of the cast-T6 alloys under different conditions of solidification are the following rules, 720℃ casting with cold iron > 720℃ casting no cold iron > 750℃ casting no cold iron. When the tensile temperature to room temperature and 150℃, the rupture of the alloy consist of cleavage planes and tear ridges; When the drawing temperature of 250℃, fracture morphology characterized dimples + a few quasi-cleavage.If solidification and heat treated as two separate factors, heat treatment effect on the tensile strength of significance is greater than the solidification conditions. Alloy solidification under different conditions of its stretching temperature sensitivity superior to the inferior order, 750℃ casting no cold iron >720℃ casting no cold iron > 720℃ casting with cold iron.