Pulse current pressure sintering of al/al₂O₃ functional graded material

This chapter discusses the pulse current pressure sintering on hardness and thermal expansion of Al/Al₂O₃ functionally graded material (FGM) This FGM consists of an aluminum layer, an α- Al₂ O₃ layer and seven intermediate layers between the two outermost layers. Aluminum and Al (OH)₃ powders are used as starting materials. Al (OH)₃ powder transformed into several types of Al₂ O₃ after the sintering process. The hardness of the intermediate layers gradually increased in proportion to the volume fraction of γ-A L₂ O₃. The top layer, which consists of α-A l₂ O₃, is about 1000 HV on average and 1500 HV at the surface. One feasible technique to improve the thermal resistance of aluminum alloy is to combine it with ceramics, which have high thermal resistance such as alumina, but the difference in the rate of thermal expansion between aluminum and alumina creates an obstacle to use them together.