Influence of solidification condition and solution treatment on fracture property of Al-Zn-Mg alloy ingots.

Abstract

The toughness of Al-Zn-Mg was a function of dendrite arm spacing and concentration of nonequilibrium secondphase. The primary and secondary dendrite arm spacing becomes smaller gradually according to an increase in cooling rate, and the toughness value becomes higher. When these materials are solution treated the toughness value increases by prolonging solution time. It depends on the solid solution of the nonequilibrium second-phase. In this case, longer solution time is necessary to obtain the maximum toughness when the initial concentration is higher. The highest toughness is achieved within short solution time when the secondary arm spacing is smaller. If the grain boundary lies at preference site of crack initiation and is propagation, the fracture toughness depends on the secondary arm spacing and is proportional to the minus one-half power of its spacing. The fracture toughness is indicated as a function of nonequilibirium second-phase particles volume fraction, and is proportional to the minus one-seventh power.