Severe grain deformation and fracture in shear-based material removal test for Ni-based superalloy

Abstract

Material loading test is a necessary approach to characterize the grain deformation and fracture mechanisms. The study of material deformation and failure mechanisms can only be conducted through purposeful deformation and destruction of the materials. However, existing material loading test methods struggle to effectively evaluate deformation states involving severe grain deformation and fracture. In this study, a new material loading test method based on shear-based material removal under the quasi-static condition was proposed. The offset loading configuration between the cutting insert and the specimen induces severe compressive and shear deformation within the deformation zones. Moreover, a microscale quasi-static-cutting (MQSC) test rig was developed to obtain the grain-scale images and microstructure information in the shear-based material removal test (SMRT). Polycrystal Inconel 718 was used as a case study to characterize the severe deformation and fracture behavior of materials. Based on the digital image correlation (DIC) technique and microscopic images taken by the MQSC test rig, the strain and stress fields were obtained to characterize the grain deformation and fracture state at the grain scale. It was found that the fracture mechanisms of Ni-based superalloy can be divided into severe shear-induced fracture and void-crack-induced fracture under severe shear deformation. The SMRT testing method provides a more intense shear and compressive deformation state, offering new insights into the behavior of grains under extreme deformation conditions.