The Low-Cycle Fatigue Behavior, Failure Mechanism and Prediction of SLM Ti-6Al-4V Alloy with Different Heat Treatment Methods

Abstract

Selective laser melting (SLM) is a promising additive manufacturing (AM) process for high-strength or high-manufacturing-cost metals such as Ti-6Al-4V widely applied in aeronautical industry components with high material waste or complex geometry. However, one of the main challenges of AM parts is the variability in fatigue properties. In this study, standard cyclic fatigue and monotonic tensile testing specimens were fabricated by SLM and subsequently heat treated using the standard heat treatment (HT) or hot isostatic pressing (HIP) methods. All the specimens were post-treated to relieve the residual stress and subsequently machined to the same surface finishing. These specimens were tested in the low-cycle fatigue (LCF) regime. The effects of post-process methods on the failure mechanisms were observed using scanning electron microscopy (SEM) and optical microscopy (OM) characterization methods. While the tensile test results showed that specimens with different post-process treatment methods have similar tensile strength, the LCF test revealed that no significant difference exists between HT and HIP specimens. Based on the results, critical factors influencing the LCF properties are discussed. Furthermore, a microstructure-based multistage fatigue model was employed to predict the LCF life. The results show good agreement with the experiment.

Effect of shot peening on fatigue behavior and microstructure of additively manufactured Co‐Cr‐Mo alloy

“…The findings presented in Figure 9 suggest that M samples with higher yield strength display elevated LCF behavior, while HT + M sample with higher strain values exhibit superior HCF behavior. These outcomes are consistent with those reported by Xi et al 37 …”

“…The findings presented in Figure 9 suggest that M samples with higher yield strength display elevated LCF behavior, while HT + M sample with higher strain values exhibit superior HCF behavior. These outcomes are consistent with those reported by Xi et al 37 The fatigue characteristics of materials are known to be susceptible to residual stresses. Because most fatigue fractures migrate inward from the surface, residual compressive stresses caused by deformation processes causing significant plastic deformation can effectively inhibit crack initiation and propagation.…”

“…These findings highlight the influence of material properties on fatigue behavior and underscore the importance of considering the appropriate fatigue regime when evaluating the performance of structural components. Previous research has indicated that samples with elevated yield strength and reduced elongation exhibit inferior fatigue strength in the HCF region yet demonstrate improved fatigue strength in the LCF region 37 . In this study, the HT + M samples underwent stress relief heat treatment.…”

“…Previous research has indicated that samples with elevated yield strength and reduced elongation exhibit inferior fatigue strength in the HCF region yet demonstrate improved fatigue strength in the LCF region. 37 In this study, the HT + M samples underwent stress relief heat treatment. Upon comparison of the fatigue test results of the M and HT + M samples, it was observed that the HT + M samples exhibited reduced fatigue life in the LCF regime (i.e., <10 5 cycles), whereas they demonstrated superior fatigue behavior in the HCF region (i.e., >10 5 cycles).…”

Anisotropy in the Tensile Properties of a Selective Laser Melted Ti-5Al-5Mo-5V-1Cr-1Fe Alloy during Aging Treatment

“…Despite the widely studied α + β alloys such as the Ti-6Al-4V alloy [ 13 , 14 , 15 , 16 , 17 , 18 ], AM of near β-titanium alloys such as the Ti-55511 alloy has attracted less attention. There are some reports on the microstructure, crystallographic texture, dislocation density, and mechanical properties of the AMed Ti-55511 alloy, which are demonstrated in Table 1 [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ].…”