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 Al 3 Zr 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 Al 3 Zr is limited at low first-step temperature (<250°C), while the transformation from L1 2 Al 3 Zr to D0 23 Al 3 Zr is simulated and high first-step temperature (≥420°C). The crystallographic orientation relationship between D0 23 Al 3 Zr precipitate (P) and Al matrix is recognized as: [001] Al //[011] P , (200) Al //(01 1 ¯) P , (020) Al //(200) P , which is different from the previous works. When the first-step temperature is 250–350°C, the dispersed η-Mg(Zn,Al,Cu) 2 phases formed during spray forming can act as heterogeneous nucleation sites of Al 3 Zr 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. [Display omitted] • The first-step pretreating temperature was crucial for pretreatment in SF 7050 alloy. • η phases promoted heterogeneous nucleation of L1 2 Al 3 Zr during pretreatment. • The orientation between D0 23 Al 3 Zr and Al matrix was identified and discussed. • Recrystallization resistance was affected by crystal structure of Al 3 Zr precipitates. [ABSTRACT FROM AUTHOR]