| The grain growth characteristics of dual-phase brass have been investigated using pure Cu, Cu -15%, -30%, -36%, -38%, -40% and -45% Zn brass which are composed of α-, β- and (α+β) dual-phase. The heat treatment has been performed at 600∼800℃ for 1∼100h and the relation between mean grain radius γ￣ and annealing time t can be described as follows : (γ￣)²-(γ￣_0)²=k₂·t (1) In the case of dual-phase brass, the grain growth needs diffusion of alloying elements, because, the chemical composition of α- and β- phase differs each other. The grains of minor phase grow in a mode of Ostwald, ripening while, the grains of major phase are restricted by pinning by the minor phase grains. In the β-rich dual-phase brass, the grain growth is controlled by volume diffusion in the α-phase, and the growth rate is expressed by the equation (2) (γ￣)³-(γ￣_0)³=k₃·t (2) In the α-rich dual-phase brass however, boundary diffusion is predominant over volume diffusion in the β-phase, and the growth rate is expressed as follows : (γ￣)⁴- (γ￣_0)⁴=k₄·t (3) |
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