Effect of Fe₃O₄ particles on thermal expansion behavior of Al₁₈B₄O₃₃ whisker reinforced aluminum composite

It is shown that the addition of Fe₃O₄ particles can decrease the coefficient of thermal expansion (CTE) of aluminum borate whisker reinforced aluminum composite. The reason is that the Fe₃O₄ particles were partially oxidized during fabrication, the oxidized Fe₃O₄ particles were reduced during the thermal expansion measurement, resulting in decreasing of the volume of Fe₃O₄ particles, which restricted the expansion of matrix aluminum and could be considered as a negative CTE reinforcement to reduce the CTE of the composite. On the basis of the measured thermogravimetric curve analysis of Fe₃O₄ particles in the composite, the change of residual stress of Fe₃O₄ particles during heat-cycling was also analyzed.