首页|Temperature-dependent yield strength and deformation mechanism of a casting Ni-based superalloy containing low volume-fraction γ′ phase
Temperature-dependent yield strength and deformation mechanism of a casting Ni-based superalloy containing low volume-fraction γ′ phase
扫码查看
点击上方二维码区域，可以放大扫码查看
原文链接
NSTL
Elsevier
? 2022 Elsevier B.V.This study investigates the temperature-dependent yield strength and deformation mechanism of a new casting Ni-based superalloy K4750. This alloy exhibits yield strength anomaly (YSA) at 650–750 °C though it contains only low volume-fraction γ′ phase (22%). Using the interrupted samples after ~1.0% plastic strain, the dominant deformation mechanisms at the initial yielding stage are identified as: (ⅰ) (anti-phase boundary)APB-coupled dislocation pairs shearing γ′ from room temperature to 650 °C, (ⅱ) dislocations bypassing γ′ and creating loops above 650 °C, and (ⅲ) dislocations overcome γ′ by the thermally activated cross-slip and local climb at 850 °C. Additionally, with the proceeding of deformation, superlattice stacking faults shearing is active above 750 °C, implying that the deformation mechanism changes as the deformation progresses. According to the theoretical calculation, the critical resolved shear stress of Orowan looping decreases faster than APB shearing with the temperature increase, which is in agreement with the observed transition of deformation mechanism. Moreover, the remaining loops hinder the movement of subsequent dislocations, resulting in severe dislocation entanglement and high dislocation density in the heterogeneous slip bands, contributing to YSA. By contrast, dislocations can easily surmount γ′ phase by cross-slip and climb at 850 °C, leading to a rapid degradation of yield strength.
NSTL
Elsevier
