Strengthening of Al 2O3/6061Al particulate composite at liquid nitrogen temperature

Abstract

Particulate reinforced Al matrix composites are of potential use in many structural applications, because of their high specific modulus, high specific strength, high wear resistance, low thermal expansion, and relatively low cost of production. Significant research has been undertaken with the purpose of increasing the authors understanding of the room and elevated temperature mechanical behavior of this subclass of composites. In contrast, little attention has been focused on their cryogenic behavior. To have a knowledge of this aspect, the present work investigates the tensile behavior of an Al{sub 2}O{sub 3}/6061 Al particulate composite at liquid nitrogen temperature. By comparing the results so obtained with those obtained at room temperature, an insight into the underlying mechanisms is discussed. Conclusions from the present study on the Al{sub 2}O{sub 3}/6061 Al composite are as follows: (1) both the naturally and artificially aged materials exhibited strength enhancement at liquid nitrogen temperature, (2) the composite exhibited well-bonded matrix-reinforcement interfaces and essentially identical deformation and fracture characteristics at both room and liquid nitrogen temperatures, (3) the markedly improved yield strength and the slightly reduced ductility of the NA material at liquid nitrogen temperature are expected to be the joint effect of the low temperature related strengtheningmore » of the 6061 Al matrix because of its f.c.c. structure and the dislocation hardening due to the enlargement of plastic zones, while the simultaneously improved cryogenic strength and elongation of the artificially aged materials are primarily due to the low temperature related strengthening.« less