Low pressure lost foam process for casting magnesium alloys

Abstract

The lost foam process is capable of making castings with extremely complicated shapes at high soundness levels and with low manufacturing costs. However, there are several challenges to produce magnesium castings using the conventional lost foam process because of the low heat content of magnesium alloys. Therefore, a novel low pressure lost foam process has been developed especially for magnesium castings, in which the melt is filled under counter gravity conditions at low pressure. This paper introduces the low pressure lost foam process. The measurement of flow profiles in the plate shape and the L shape EPS patterns under different conditions reveals that the process can offer unique advantages for achieving laminar flow and fully controlled flow during melt filling. The dimensional accuracy with the specially designed castings shows that CT4–8 is achievable for magnesium castings produced by the low pressure lost foam process, according to the dimensional tolerance grading given in ISO8062–1994. A comparison and Weibull statistics analysis of the mechanical properties of AZ91E alloy confirms that the low pressure lost foam process gives comparable yield strength, ultimate tensile strength, and elongation to the conventional precision sand process.