The Research On Magnesium Alloy Semi-solid Non-dendritic Structure And Die Casting Process

At present the application of magnesium alloy components in the solution are within the limitation of Solid solubility, the dissertation has breakthrough of tradition with choosing Hypo-eutectic scope, using AZ91D method for the transformation boldy. It is a difficult point to how to prepare suitable for the processing of semi-solid alloy magnesium alloy billets. This way makes semi-solid isothermal treatment of non-dendritic structure blank Preparation and reheating the merger become a step, but preparation and control blank is inevitable. Therefore, the choice of the aluminium are respective 15%, 20%, 25%, these three different ingredients of magnesium alloy. which has been done more group testing, the initial pre-trial proved the feasibility of this option. Finally, getting a structure of semi-solid non-dendritic with Thixotropy .This paper in with of prepares semi-solid billets through the isothermal treatment, which has studied the aluminiferous 20% and 15% magnesium alloy semi-solid process characteristics Thixo-casting .The tradition chamber can not been used in semi-solid diecasting, now, the condition has changed, because the chamber which designed for semi-solid diecasting was used in the experience. The heated chamber can keeps the semi-solid alloy in higher temperature and delays the freezing speed. The excellent fluidity of the alloy fit the semi-solid diecasting of magnesium alloy. The influences of filling speed and pressure of die-casting and mold temperature was investigated to mechanical properties and organization's influence of alloy.Two parameters fixes in the good parameter,studys influence of the third parameter. The result indicated that mechanical properties of the best when injection pressure of 40 MPa, injection speed of 4 m/s, mold temperature at 160℃.The tensile strength has the maximal of 220MPa and the elongation is 5.63% and hardness is 98.5HB and impact toughness is 8.53J/cm~2.After T4 treatment, the tensile strength increased to 238MPa, elongation is 6.71%. Thixocasting forming the organization more evenly distributed.The fracture morphology of tensile tested specimens has analysed. The result indicated that the fracture morphology of the semi-solid diecasting was along grain boundaries mainly.For purposes of comparison, by orthogonal experiments on 15% of the liquid alloy die-casting process.The results show that the factors influencing on properties of 15% from the greatest to the smallest are following: on tensile strength are injection speed, mould temperature, pouring temperature and injection pressure; on elongation are pouring temperature, mould temperature, injection speed and injection pressure. In the experiment, the mechanical properties of 15% magnesium alloy were obtain preferable value, at the proper factors: pouring temperature is 650℃, mould temperature is 150℃, injection speed is 3.5m/s, injection pressure is 75MPa. For 20% of liquid alloy die-casting, the average tensile strength of 190 MPa, the average rate of 3.19% extension. We can observe carefully the break surface by means of SEM, the fracture morphology of tensile tested 15% magnesium alloy is cleavage fracture, and pull break surface as same as impact break surface. There are many porosities and different crack.