Orientation of silicon particles in a binary Al–Si alloy

摘要

The orientations Si-crystals take in aluminium, in an alloy with composition Al–1.3at%Si, were investigated by transmission electron microscopy. Hardness was measured for isothermal heat-treatments at 175 °C and 260 °C. Conditions analysed by TEM were 17 h at 175 °C and an additional 3 h at 260 °C, both containing a high density of small Si-crystals, the finest corresponding to 175 °C. Two main orientation relationships were found: (001)Al || (001)textSi, [100]Al || [100]textSi and (001)Al || (110)textSi, [1 [`1] [`1]] textSi || [010]textAl.(001)hbox{Al},||,(001)text{Si}, [100]hbox{Al},||,[100]text{Si} hbox{ and } (001)hbox{Al},||,(110)text{Si}, [1;overline{1};overline{1}] text{Si},||,[010]text{Al}. The first accounted for approximately 60% of Si precipitates in condition 17 h_175 °C. Despite a high number density and well-aligned interfaces, the Si precipitates have negligible influence on hardness. Findings are consistent with Ge particles in Al–Ge alloys.