Effective method to simultaneously release residual stress and promote planarization of surface indentation achieved by secondary indentation

Abstract Regarding the surface residual stress and accompanied pile-up phenomenon produced during indentation, a novel method was proposed to effectively release residual stress and promote surface planarization. The procedures included an initiation indentation by using Vickers indenter and a secondary indentation at nano-scale on already formed surface by using a cube-corner indenter. Both finite element analysis and indentation experiments revealed significant stress release and surface planarization, which were closely dependent with the indentation depth and location. A 33.03% stress reduction and an internal energy reduction of 6.04 × 10−8 J were obtained through finite element analysis. Meanwhile, due to the effect of secondary indentation, the average residual stress and crystallinity of AlSi7Mg0.3 alloy specimen were reduced by 64.09% and 49.72%, respectively, which was calculated by X-ray microdiffraction (μXRD), the atomic force microscopy (AFM) micrographs of initiation and secondary indentation edges also indicated a pile-up reduction with 368.7 ± 46.1 nm, which verified the planarization through the comparison of pile-up displacements between symmetrical paths.