Cu-30 mass%Zn合金の多軸鍛造により形成される超微細結晶粒組織とその熱的および機械的特性

Abstract

A Cu-30 mass%Zn alloy was multi directionally forged (MDFed) at 300 K and 77 K. Dislocation walls, subboundaries and grain boundaries were gradually developed with increasing strain to form ultra fine grains (UFGs). Furthermore, the evolution of UFGs was drastically stimulated by mechanical twinning. Therefore, it was revealed that the grain refinement in a Cu-Zn alloy during MDF was induced by both mechanisms of mechanical twinning and continuous dynamic recrystallizatrion. When MDFed to a cumulative strain of ΣΔe=6, the grain size obtained was 18 nm at 77 K and 22 nm at 300 K. The MDFed alloy exhibited almost constant ductility irrespective of cumulative strain and MDF temperature, while the tensile strength increased monotonically with increasing cumulative strain. Thermal stability of the UFGed Cu-Zn alloy decreased with increasing cumulative strain and decreasing MDF temperature.