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

• Published in: Applied surface science 2020-04, Vol.509, p.144712, Article 144712
• Main Authors: Ma, Zhichao, Jiang, Dongying, Zhao, Hongwei, Qiang, Zhenfeng, Zhang, Zhihui, Liu, Dongni, Ren, Luquan
• Format: Article
• Language: English
• Subjects: Elastic energy; Nanoindentation; Pile-up; Residual stress; Surface planarization
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.144712

[Display omitted] •Simultaneous residual stress release and planarization of surface indentation.•Rapid release of internal energy trough by secondary indentation.•Adjacent to the edge, the convex shape facilitates the plastic flow and stress release. 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.