As a part of a project of improving the hot tearing resistance of the aerospace casting aluminum alloy A201, this thesis focuses on the effect of melt treatment, alloying elements, the addition of mischmetal and use of a magnetic field on the hot tearing of a number of alloys based on the Al-Cu system. Melt treatments such as grain refinement improves the hot tearing resistance marginally. In the case of alloying additions, magnesium was found to be detrimental to hot tearing. Mischmetal improves the hot tearing resistance of AlCu-Mg alloy quite significantly. Thermal analysis has shown that, Mischmetal (a cerium and lanthanum-based alloy with rare earth solutes as shown in Table 3.7) additions reduces the solidification range of the Al-Cu alloys. Optical microscopy and SEM micrographs reveal that Mischmetal modifies the eutectic phase and refines the microstructure of the alloy. Grain refining experiments were conducted using Al-Ti-13 master alloy and Mischmetal to find out the optimum amount of Al-Ti-13 which produces the finest structure, and to compare the effect on each grain of the structure. Tensile samples were cast and the results showed that Mischmetal additions increase the strength of the A201 alloy, however, the hardness was found to be decreased with increasing Mischmetal percentages.
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