The effect of elevated temperature exposure on fracture resistance and fracture path in a precipitation strengthened aluminum alloy

摘要

There is currently significant interest in increasing the allowable service temperatures of aluminum alloys[ 1,2]. Unfortunately, precipitation strengthened alloys present special problems with regard to elevated temperature service. Generally, the microstructures of precipitation strengthened alloys are not stable for long times at elevated temperature [ 1,3-S]. Previous studies have shown that tensile strength and ductility are not adequate indicators of microstsuctural stability [7,8]. Tensile properties may remain nearly constant, while fracture toughness degrades significantly after elevated temperature exposure. Frac- ture path changes from transgranular to ductile or brittle intergranular/intersubgranular have been ob- served [7,8]. The use of precipitation strengthened aluminum alloys for elevated temperature applications will therefore require better understanding of the related mechanisms of microstructural evolution and property degradation. The objective of the present study is to assess the effect of thermal exposure on the fracture properties of an Al-Cu-Mg-Ag alloy and relate those properties to the fracture path and to grain boundary precipitation.