Effects of thermal processing on thermal expansion coefficient of a 50 vol.% SiCp/Al composite

Abstract

Abstract The thermal expansion coefficients (CTE) of a 50 vol.% SiCp/Al composite prepared by a squeeze casting route were measured and examined from room temperature to 600°C using thermomechanical analysis (TMA) method, under the conditions of as-cast (AS), water-quenched (WQ), furnace-cooled (FC) and air-cooled (AC). The influence of thermal processing on CTE of the SiCp/Al composite was studied in terms of thermal residual stresses generated upon cooling from the processing temperature. It is found that the introduction of high volume fraction of SiC particles to Al matrix could notably reduce the CTE of matrix, leading to the low CTE values of the composite either at room temperature or at high temperature. The CTEs of both the composite and the unreinforced Al matrix increase with increasing of temperature, while the composite shows a much slower increasing rate than the unreinforced Al matrix resulting from the restriction of SiC particles on Al matrix during thermal expanding process. The thermal expansion behavior of the SiCp/Al composite is influenced by the previous thermal processing history. The WQ and AS specimens present lower CTEs compared to the FC and AC ones, which is thought to be due to the difference in original thermal residual stresses within these specimens and their releasing behavior during subsequent heating.