New insight into precipitation of Al3Zr and correlative effect on recrystallization behavior in a rapidly-solidified Al-Zn-Mg-Cu-Zr alloy

The influence of temperature of first-step pretreatment on the precipitation and crystal structure of Al3Zr in a spray-formed (SFed) Al-Zn-Mg-Cu alloy was systematically explored. With different first-step pretreatments, the microstructure evolutions during hot extrusion and solution treatment were studied. The results show that pretreatment before hot-working is necessary for rapidly-solidified Al-Zn-Mg-Cu alloy and temperature of first -step pretreatment is crucial for stabilizing microstructures. In detailed, the homogenous nucleation of L1(2) Al3Zr is limited at low first-step temperature (< 250?C), while the transformation from L12 Al3Zr to D023 Al3Zr is simulated and high first-step temperature (>= 420?C). The crystallographic orientation relationship between D023 Al3Zr precipitate (P) and Al matrix is recognized as: [001](Al)//[011](P), (200)(Al)//(011)(P), (020)(Al)//(200)(P), which is different from the previous works. When the first-step temperature is 250-350?C, the dispersed eta-Mg(Zn,Al,Cu)2 phases formed during spray forming can act as heterogeneous nucleation sites of Al3Zr precipitation. The recrystallization resistance of SFed Al-Zn-Mg-Cu alloy during solution treatment is markedly enhanced by an optimized pretreatment of 250?C@36 h + 470?C@24 h.

Automated summary

The influence of temperature of first-step pretreatment on the precipitation and crystal structure of Al3Zr in a spray-formed Al-Zn-Mg-Cu alloy was systematically studied. The results show that the temperature of first-step pretreatment is crucial for stabilizing microstructures, and an optimized pretreatment can significantly enhance the recrystallization resistance during solution treatment.