| Automobile industry is one of the key industries for China's economy. The domestic production of automobiles in china is more than 10 million, which reflects the domestic market is huge and has a bright future. As the fourth important material applied in automobile industry, magnesium alloys have advantages such as: low density, high strength weight ratio, good machinery. It can help solve problems that automobile industry encounters, which include high oil price and rigorous policies on energy saving, carbon emission reduction and materials recycling.Most magnesium alloys are produced by pressure die casting, which brings many pores in parts. Pores inside mean low strengths and inable to be heat treated. The most widely used magnesium alloys in automobiles are Mg-Al alloys, creep property of which is bad. Consequently, Mg-Al alloys can't work under high temperature for long time. All these factors inhibit the application of magnesium alloys in automobiles.In order to solve these problems, China, USA and Canada initiate a project-"Magnesium Front End Research and Development Project". Magnesium alloys are introduced to fabricate front end parts in automobiles instead of aluminum alloys and steel.As a branch of this project, this paper avails of vacuum die casting and horizontal squeeze casting to manufacture magnesium alloys parts to eliminate pores and enhance the strengths, including optimizing the manufacturing parameters and studying on how manufacturing methods, alloy component, heat treatment influence on parts'properties. And the main conclusions are listed as below:Both AZ91D and AM60 products'microstructures are comprised ofα-Mg matrix and Mg17Al12 eutectic along the boundary. After solid solution, the eutectic phase dissolves into the matrix and precipitates after aing. For AZ91D, the supersaturated Al precipitates from the boundary into grains discontinuously in the form of Mg17Al12 eutectic, which strengthes the matrix and enhances the mechanical properties. But AM60's supersaturated Al precipitates in the boundary and grains in a granular form, which means its mechanical properties are not so good as AZ91D. The strength of AZ91D is higher than that of AM60 while the elongation is less for the latter one has less Mg17Al12 eutectic phase precipitateing in solidifying. After solid solution, all Al dissolves into the matrix, so AZ91D's elongation is equivalent to that of AM60. The grains grow bigger as solid solution goes on. Accordingly, yield strength and elongation stay the same while ultimate tensile strength decreases a little. Vacuum die casting can not so effectively eliminate shrinkages in products as the pores, especially in thick part. Only by optimizing the products'structure and modules'design can reduce these shrinkages.On the other hand, Mg-Nd-Zn alloy's grain size and mechanical properties reach to a peak as the casting pressure or injection velocity increases and then drop. In the case of this alloy, the best casting pressure is 70MPa and the best injection velocity is 4MPa. Horizontal squeeze casting performs as well in refining the grains of Mg-Nd-Zn alloy as adding Zr element. It also cuts the cost. In addition, the products of horizontal squeeze casting have higher mechanical properties than products by gravity casting. According to the test, the best solid solution should be 6 hours under 500℃. Meanwhile, the aging treatment shoule be 10h under 200℃. There still exist shrinkages in the products for the pressure in squeeze casting hasn't been optimized, which needs further study.
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