Al-Mg-Si鋁合金拉伸性質與可靠度之固溶化處理效應

Abstract

6xxx-series aluminum alloys are age hardening alloys which have many excellent properties, such as light weight, good formability, high specific strength and good resistance to corrosion. They are widely used in transportation applications, for instance, automobiles, aircraft industry, and architectures as well. The main precipitation phase of the series is Mg2Si and the conditions of heat treatment will have a great impact on the mechanical properties. In this study, we apply solid solution treatment and then use the artificial aging treatment (T6). The higher temperature of solid solution will have larger amount of solid solution, but it will also lead to the problem of remelting second phase. Therefore, the tensile properties of T6 treatment 6066 and 6067 aluminum alloys taking two different solid solution temperatures will be discussed. In addition, reliability is an important property and it will be estimated by Weibull analysis. According to the tensile testing, T6 treatment 6066 aluminum at solid solution temperature of 520℃ has higher strength than that at solid solution temperature of 550℃ by 100MPa. This may caused by the Q phase which left the tiny voids in alloy when 6066 aluminum took solid solution temperature of 550℃. However, 6067 aluminum may have the opposite condition. It has higher strength under solid solution temperature of 520℃. This was probably due to the higher precipitates density. On the other hand, both two alloys have good ductility when taking solid solution temperature of 550℃. In this study, 6067-HCu aluminum was used to verify the Q phase effect in chapter 5. In terms of reliability, this study used Weibull analysis to estimate the YS and TE properties which took solid solution temperature of 550℃. Observation indicated that for both YS and TE, 6066 aluminum has a constant failure rate, and it may be due to the Q phase. However, 6067 aluminum has an increasing failure rate, and it has better reliability than 6066 aluminum. Furthermore, 6067-HCr aluminum was used to verify the effect of hard phases on reliability in chapter 5.