Al and Mg Alloys for Aerospace Applications Using Rapid Solidification and Powder Metallurgy Processing

摘要

The work performed during the past three years has involved studies of some elevated temperature Aluminum and Magnesium alloys, and in addition a preliminary study of intermetallic compounds based on Al3X, where X is Ti, V, and Ni+Ti. In the case of the Al alloys, this work was in essence a continuation of the work performed during the preceeding three years of study, where rapid solidification processing (RSP) of Al alloys was investigated. Two areas were investigated, one involving alloys which might exhibit high elastic moduli, and the second concerned the improvement in fracture toughness when Si is added to Al-Fe-Mo alloys. It was found that the modulus increases Al-Be alloys processed by rapid solidification were as expected from theory, whereas those for Al-Mn alloys were somewhat below expectation. This latter result was attributed to casting porosity present in our samples. In terms of the AL-8Fe-2Mo-Si alloys (where both 0.5% and 1.0% si have been added), the development of microstructure following RSP has been studied in alloys with, and without, the Si additions. The presence of Si resulted in the information of the compound alpha-ALFeSi, with space group determined to be Im3 by convergent beam electron diffraction. The morphology of the precipitates of this compound were found to be approximately spherical and when compared with the lenticular precipitates in the case of consolidated Al-8Fe-2Mo, this shape is thought to account for the difference in fracture toughness results. Keywords: Powder metallurgy, Powder compaction. (aw)