Zn-Al合金における加工中の析出，回復再結晶と加工軟化

Abstract

In Zn-Al alloys, work-hardening in Al-rich alloys and work-softening in Zn-rich alloys were observed respectively. The micro-Vickers hardness of work-softened specimens was increased and, on the contrary, that of work-hardened-specimens was decreased by solution treatments. The electrical resistivity was increased by solution treatments in both work-softened and work-hardened specimens. The structures of cold-rolled textures and those in the midst of recovery and recrystallization were observed in the work-hardened and work-softened specimens, respectively. In the work-softened alloys, the lattice parameters of the Al-rich phase were determined by X-ray diffraction to be in approximate agreement with that of pure Al, and those of the Zn-rich phase, in agreement with that of pure Zn. Age-hardening was observed and the electrical resistivity increased in the work-hardening Al-rich alloys when aged at room temperature after solution treatments. On the other hand, age-softening was observed and the electrical resistivity decreased in the work-softening Zn-rich alloys. These experimental results provided the evidence for the precipitation, recovery and recrystallization during working. Based upon these discussions, the mechanism of work-softening in Zn-Al alloys is as follows: Cold-working causes the precipitation of dissolved Al, which results in the lowering of recrystallization temperature and the work-softening occurs due to the recovery and recrystallization at room temperature.