Comprehensive investigation of residual stress in selective laser melting based on cohesive zone model. (June 2022)

• Record Type: Journal Article
• Authors: Zou, Sheng; Xiao, Xinyi; Li, Zongchen; Liu, Min; Zhu, Chao; Zhu, Ze; Chen, Chentong; Zhu, Feng
• Is Part Of: Materials today communications. Volume 31(2022)
• Publication Date: 2022-06
• Subjects: Ti-6Al-4V -- Residual stress -- Selective laser melting -- Analytical model -- Cohesive zone model; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2022.103283
• Languages: English
• ISSNs: 2352-4928

Abstract

Abstract: The residual stress in selective laser melting (SLM)-printed structures may induce cracks and distortions, and has been widely investigated. However, the focus of most of previous studies has been on the distribution of residual stress after the SLM process rather than on the evolution of stress and strain during the process. The temperature gradient mechanism, which is commonly used to qualitatively evaluate residual stress distribution, lacks theoretical proof and cannot be used to obtain the function of residual stress and process parameters. This study takes the commonly used Ti-6Al-4V titanium alloy as the research object. A numerical model that involves phase transitions and Marangoni effect considerations is proposed and verified by experimental results. The distributions and evolutions of stress and strain during the SLM process with different scan lengths, scan speeds, and hatch spaces are investigated. Furthermore, a cohesive-zone-model-based analytical model is established to reveal the functional relationship between the residual stress and process parameters and to analyze the results. The results indicate that the residual stress is determined by the scan length, plastic strain, fusion zone (FZ) dimension, and interface displacement. The longitudinal maximum stress is located in the middle of the FZ and it increases as the scan length increases. When the scan length exceeds 3 mm, the rate of increase of the peak residual stress with respect to the scan length decreases rapidly. As the scan speed increases from 500 mm/s to 1000 mm/s, the width of the high-stress zone increases from 3.6 mm to 4.1 mm. The residual stresses under multiple scanning conditions are 25% lower than that of a single track. In addition, the residual stress increases slightly with the hatch space. This work can provide a new insight into the understanding of the residual stress in the SLM process and help to rationally plan the process to reduce residual stress.