Article
Engineering, Mechanical
Tao Gao, Hongqian Xue, Zhidan Sun, Delphine Retraint, Yanli He
Summary: The fatigue behavior and damage mechanisms of a Ti-8Al-1Mo-1V alloy were investigated in the very high cycle fatigue (VHCF) regime. It was found that the crack initiation area is characterized by nano-marking facets and flat facets induced by slip activity. The large scatter in fatigue life can be attributed to slip inhomogeneity.
INTERNATIONAL JOURNAL OF FATIGUE
(2021)
Article
Engineering, Mechanical
Weiqian Chi, Gen Li, Wenjing Wang, Chengqi Sun
Summary: This study investigates the very high cycle fatigue behavior of additively manufactured Ti-6Al-4V material under different stress ratios. The fracture surface analysis reveals the presence of a fine granular area (FGA) with discontinuous regions of nanograins in the crack initiation and early growth region. The crack growth rate in the FGA can be used to predict the fatigue life.
INTERNATIONAL JOURNAL OF FATIGUE
(2022)
Article
Materials Science, Multidisciplinary
Tao Gao, Xu Zhao, Hongqian Xue, Zhidan Sun
Summary: The fracture surface characteristics and micromechanisms of fish-eye crack initiation in a Ti-6Al-4V alloy under VHCF loading were investigated. The crack initiation area exhibited ragged-like mountains, dimples, and various irregular rods/particles, grooves, and microvoids. These characteristics were primarily attributed to the nucleation and coalescence of microvoids and grooves at the alpha(s)/beta(r) interface inside the beta(trans). The beta(trans) played a dominant role in the fish-eye crack initiation and early propagation process.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Nanoscience & Nanotechnology
Xiaolu Gui, Guhui Gao, Baifeng An, R. D. K. Misra, Bingzhe Bai
Summary: The study investigated the effects of inclusion size and microstructural features on HCF/VHCF in a B/M steel. It was found that fatigue crack initiation was mainly influenced by inclusions, with the majority of fatigue life consumed by the crack initiation process regardless of the source of the crack. The ratio of fatigue crack initiation life to total fatigue life exhibited a wide scatter due to variations in the B/M hierarchical structure within individual prior austenite grains when cracks initiated from sub-surface microstructure.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Nanoscience & Nanotechnology
Zhihong Wu, Hongchao Kou, Jinshan Li, Nana Chen, Zhicheng Xi, Fan Sun, Frederic Prima
Summary: In this study, low-cycle fatigue tests were conducted on the dual phase titanium alloy Ti-5Al-7.5V at room temperature to investigate the deformation mechanisms and crack initiation. It was found that planar dislocation slip, localized at the basal and prismatic planes of the alpha phase, was the primary deformation mode. Multiple slips occurred simultaneously within a single grain. Microcracks were observed along the basal slip bands, but were confined within the primary alpha grains without propagating to the surrounding transformed beta matrix. The presence of silicides in contact with the microcracks and slip bands did not lead to crack initiation. It remains unclear whether the silicides can act as dislocation sources for planar slips and facilitate crack nucleation.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Nanoscience & Nanotechnology
Alice Cervellon, Chris J. Torbet, Tresa M. Pollock
Summary: The anisotropic fatigue properties of three Ni-based SX superalloys were investigated in the very high cycle fatigue regime. The [111] orientation showed higher fatigue lives at high stresses but lower fatigue lives at very low stresses. The resolved shear stress on the octahedral slip systems and the pseudo-cube slip in the matrix were identified as the main reasons for the anisotropy effect.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Materials Science, Multidisciplinary
Guhui Gao, Rong Liu, Yusong Fan, Guian Qian, Xiaolu Gui, R. D. K. Misra, Bingzhe Bai
Summary: This study investigates the fatigue crack initiation behavior of advanced bainitic steels during high cycle fatigue/very high cycle fatigue regimes and the role of retained austenite in crack initiation and propagation. The study identifies multiple micro-mechanisms responsible for fatigue crack initiation and discusses the formation of fine grains that assist crack advancement. The findings provide insights into the cyclic response of multiphase structures and the mechanisms of fatigue crack initiation during very high cycle fatigue.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2022)
Article
Nanoscience & Nanotechnology
Jialong Tian, Wei Wang, Huabing Li, Ke Yang, Zhouhua Jiang
Summary: The microstructure and high cycle fatigue property of maraging stainless steels with Ti addition were studied. The crack initiation mechanism in HCF depends on the value of normalized applied stress, where high NAS is controlled by yield strength dominated by nano-size precipitates and low NAS is controlled by the distance between TiN inclusion and specimen surface.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Engineering, Mechanical
Leiming Du, Xiangnan Pan, Guian Qian, Liang Zheng, Youshi Hong
Summary: The crack initiation mechanisms of a selective laser melted Ti-6Al-4V alloy were investigated under two stress ratios and up to very-high-cycle fatigue (VHCF) regime. Different types of defects induced crack initiation under different stress ratios, and a nanograin layer formed underneath the crack initiation region for VHCF cases at R = -1, contributing to fatigue life extension.
INTERNATIONAL JOURNAL OF FATIGUE
(2021)
Article
Materials Science, Multidisciplinary
Zhihong Wu, Hongchao Kou, Nana Chen, Zhixin Zhang, Fengming Qiang, Jiangkun Fan, Bin Tang, Jinshan Li
Summary: The study investigated the effect of microstructure features on the high-cycle fatigue behavior of Ti-7Mo-3Nb-3Cr-3Al (Ti-7333) alloy. It was found that fatigue strength is closely related to microstructure features, especially the alpha(p) percentage. The alloy with lower alpha(p) percentage exhibited higher scatter in fatigue data and bimodal fatigue behavior.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2021)
Article
Engineering, Mechanical
Chen Chen, Tao Gao, Tianyue Chen, Bin Li, Zhi Qin, Rui Chen, Hongqian Xue
Summary: This study investigated the fatigue crack initiation mechanism of equiaxed Ti-6Al-4V alloy in the very high cycle fatigue (VHCF) regime. Ultrasonic fatigue experiments were conducted on Ti-6Al-4V specimens and a detailed analysis of the failure mechanism was carried out using scanning electron microscopy (SEM). The crystal plasticity finite element (CPFE) method was used to investigate the localized cyclic plastic response of the alloy and the impact of the βt phase on VHCF behavior.
ENGINEERING FAILURE ANALYSIS
(2023)
Article
Engineering, Mechanical
Chengqi Sun, Weiqian Chi, Wenjing Wang, Yan Duan
Summary: This study investigates the very high cycle fatigue behavior of an additively manufactured Ti-6Al-4V using different fatigue tests, finding that crack initiation is related to loading types. The mechanism of crack initiation and early growth in VHCF regime is proposed to be attributed to grain refinement caused by dislocation interaction. The fatigue performance of the AM Ti-6Al-4V is comparable to conventionally processed Ti-6Al-4V.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2021)
Article
Materials Science, Multidisciplinary
Donghyuk Kim, Rong Jiang, Ian Sinclair, Philippa Reed
Summary: The effects of unimodal secondary gamma' size and grain orientation on fatigue crack initiation and early crack propagation at room temperature were investigated in RR1000 alloy. The results showed that cracks mainly initiated at slip bands and/or pores followed by crystallographic facet formation. More diffuse strain localisation around the pores was observed by SEM-DIC analysis. Fatigue lifetime was found to be linked to the number of crack initiations and consequent crack coalescence, which accelerated crack propagation. Slip trace analysis with EBSD mapping indicated that cracks are likely to propagate along the primary active slip system with a relatively high Schmid Factor. In the conducted tests, the stochasticity of crack initiation events had a greater impact on overall lifetime than variations in secondary gamma' size.
MATERIALS SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Mechanical
S. Hemery, J. C. Stinville
Summary: This study monitored the microstructurally small crack growth in Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo with equiaxed and bimodal microstructures. The influence of microstructure on the lifetime variability observed in Ti alloys was evaluated, and primary alpha grains, basal plane cracking, and misalignment across boundaries were identified as key features for high crack growth rates. Dwell periods were found to induce significant small crack acceleration.
INTERNATIONAL JOURNAL OF FATIGUE
(2022)
Article
Materials Science, Multidisciplinary
Zhi Qin, Bin Li, Chen Chen, Tianyue Chen, Rui Chen, Han Zhang, Hongqian Xue, Changfeng Yao, Liang Tan
Summary: The study investigated the high cycle and very high cycle fatigue behavior of the GH4169 superalloy. The results showed that failures in different fatigue regimes had different initiations, and significant strain localization occurred at the twin boundaries of the material under fatigue cyclic loading.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)