| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 97 === Lightweight A384 aluminum alloy with high silicon content has good casting property for its good flowing of the liquid phase. Due to the advantages of high temperature and high erosion resistances, it can be used in the main carrier of the wind turbine. The as-cast A384 aluminum alloy with full-annealed treatment (represented as BM) was used as the base metal in this study. The BM specimens with friction stir processing (FSP) and peak aging treatment after FSP were used for studying the erosion properties of these specimens.
It is recognized that four segregate phases are exhibited in the casting A384 alloy, including Si particles, τ1 (Al9FeNi), ���n�vAl3CuNi) and Q (Al5Cu2Mg8Si6) precipitate phases. According to the experimental results, all of the specimens show a higher erosion rate at the oblique erosion impact angle. This phenomenon reveals that a characteristic of the ductile erosion. The second phases are precipitated and aggregated within DAS in the BM specimens that are easily to form a soft zone. The increasing erosion rate is owing to the soft zone cut by the erodent. Instead, the erosion resistance is increased after FSP. The refined and uniformly distributed second phases, which are resulted from the FSP, can help to increase the hardness and further reduce the brittle fracture of the specimens. Si and ���n�vAl3CuNi) phases are usually found near or end of the grooves with little fracture. But the τ1 (Al9FeNi) phase is easier to be removed by the erodent cutting. It can be inferred that Si and ���n�vAl3CuNi) are useful to improve the erosion resistance of A384 aluminum alloy, but τ1 (Al9FeNi) phase is detrimental for the erosion resistance of A384 aluminum alloy. Moreover, the maximum erosion of the BM and FSP specimens after peak aging treatment will be decreased. The hardness and the deformation resistance of peak aged specimens are increased. They have a brittle fracture tendency that the maximum erosion rate transfers 5 degree with decreasing ductility.
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