Cyclic-HPT加工により得られる定常結晶粒径に及ぼす1パスひずみの影響

抄録

The effect of one-pass strain, |±Δε|, on grain refinement was systematically investigated by cyclic - HPT straining with a repetitive deformation process in which positive and negative shear strain are introduced. The steady-state grain size, d_ss, depended on |±Δε| rather than the given total strain, Σ |±Δε|. The unstable dislocation cell walls formed by positive strain, +Δε, was discomposed by negative strain, −Δε. The stability of dislocation cell wall increased as the number of dislocations introduced by applying |±Δε| in a grain, n, increased. The decrease in n was caused by decreasing +Δε and grain size. It was found that n affected the stability of dislocation cell walls and was an important factor in determining d_ss.

Fig. 7　Relationship between the number of dislocations introduced by one-pass strain |±Δε| in one grain n and grain size d. The n at the steady-state grain size d_ss in c-HPT (|±Δε| < 3) were plotted. Each |±Δε| is indicated by a color in the color bar.