Effect of One-Pass Strain on Steady-State Grain Size by Cyclic - HPT Straining

Abstract

The e ff ect of one – pass strain, | ± Δε |, on grain re fi nement 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 a ff ected the stability of dislocation cell walls and was an important factor in determining d ss . ［ doi:10.2320 / jinstmet.J2020045 ］