Effect Of Die Cast Technics On Microstructure And Properties Of AM60B Magnesium Alloys

Magnesium alloys are the lightest metals that have been used in practice. Because of lower density ,high ratio of strength to density and others advantages, Magnesium alloy is an important Engineering structure materials used widely to produce 3C (computer, communication and consumption) and automobile products .Research works of this thesis aim at die cast magnesium alloys AM60B and mainly focus on the effects of die cast technic parameter on them. Die cast magnesium alloy are investigated systematically for the relations of their technics, microstructures, mechanical properties and heat treatment, microstructures, mechanical properties. And the effects of different technics on the fluidity and the trend of hot crack, which are thin plane, of magnesium alloys are discussed.An orthogonal experiment was used to evaluate the influence of die casting parameters on die cast technics of AM60B magnesium alloy. The results show that the factors influencing on properties of AM60B from the greatest to the smallest are following: on fluidity are injection specific pressure, pouring temperature, mould temperature and die filling speed; on tensile strength are pouring temperature, injection specific pressure, mould temperature and die filling speed; on elongation are die filling speed, pouring temperature, mould temperature, injection specific pressure; on impact toughness are die filling speed, pouring temperature, injection specific pressure, mould temperature; on HB hardness are pouring temperature, mould temperature, injection specific pressure, die filling speed. After analyse all die cast parameter, in the experiment, the mechanical properties of Mg die-casting AM60B were obtain preferable value, at the proper factors: pouring temperature is 680℃, mould temperature is 170℃, die filling speed is 3.0m/s, injection specific pressure is 95MPa.Heat treatment is fit for AM60B alloy, but the temperature must be rigid and after heat treatment, there are some common defects in the die-castings, such as surface ablation, dunk, oxidation, and grain boundaryburn partly.We can observe carefully the break surface by means of SEM, the fracture patterns of die cast magnesium alloy AM60B is cleavage fracture, and pull break surface as same as impact break surface. There are many porosities and different crack.The thin wall die-castings are prone of hot crack and the hot crack trend was affected by mutual relation between pouring temperature, mould temperature and die filling speed. In the experiment, the least hot crack can be obtained at the proper value: pouring temperature is 680℃, die filling speed is 3.0m/s and injection specific pressure is 95MPa.