In situ observation of interfacial fatigue crack growth in diffusion bonded joints of austenitic stainless steel

Li, Shuxin; Xuan, Fu‐Zhen; Tu, Shan‐Tung

doi:10.1016/j.jnucmat.2006.12.026

Cited by 26 publications

(6 citation statements)

References 20 publications

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“…The bonding interfaces are generally weak and are prone to the formation of cracks and voids. Discrete microvoids were observed at diffusion-bonded joints where fatigue crack initiation occurs [12].…”

Section: Micro-heat Exchangermentioning

confidence: 99%

Exploring the fabrication limits of thin-wall structures in a laser powder bed fusion process

Narra

Rollett

2020

Int J Adv Manuf Technol

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Although additive manufacturing (AM) is becoming increasingly popular for various applications, few studies have addressed design and potential problems in thin wall fabrication for the laser powder bed fusion (LPBF) process. In the LPBF process, rapid cooling induces thermal shrinkage, which in turn, results in high residual stress and complicates thin wall fabrication. The minimum wall thickness is limited by the parameters and machine settings while the dimensional accuracy is controlled by the powder size, scan strategy, and part geometry. The ability to fabricate thin-wall components is important for applications such as heat exchangers (HX). This study explores the performance of the LPBF process by fabricating thin walls with extreme geometries in different processing conditions and alloys using an EOS M290 LPBF machine. Results show that the material, part design, and scanning strategy contribute to the variation in thin wall dimensions. A maximum inclination angle of 60°and a minimum wall thickness of1 00 μm in Ti-6Al-4V, Inconel 718, and AlSi10Mg were achieved using optimized part design and processing conditions. The effects of part design and material on the thermal distortion and surface finish of thin walls were also investigated leading to a discussion on how the scan mode assigned by the EOS software affects design and fabrication. Additionally, synchrotron-based X-ray micro-tomography (μSXCT) was utilized to quantify the porosity in thin-wall structures and to correlate it with the integrity of the structures. Comprehensive design guidelines presented in this work can increase the success rate of fabricating thin-wall geometries. Keywords Additive manufacturing (AM). Laser powder bed fusion (LPBF). Thin wall. Design guidelines. Porosity. X-ray computed tomography (XCT) Abbreviations AM Additive manufacturing LPBF Laser powder bed fusion μSXCT Synchrotron-based X-ray micro-tomography CAD Computer-aided design μHX Micro-heat exchanger XCT X-ray computed tomography EDM Electrical discharge machining APS Advanced Photon Source

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Section: Micro-heat Exchangermentioning

confidence: 99%

Exploring the fabrication limits of thin-wall structures in a laser powder bed fusion process

Narra

Rollett

2020

Int J Adv Manuf Technol

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“…Comparatively, the joint diffusion-bonded at 1110 °C has superior tensile strength and elongation of 1045 MPa and 22.7%, as illustrated in Figure 7. The apparent microvoids and frail diffusion zones in the joints obtained at low temperatures limited the joint performance [25,29,30]. Both tensile strength and elongation of the joint were improved with bonding temperature elevated to 1110 °C due to high temperature promoting the elimination of microvoids and formation of a sturdy diffusion zone, which sufficiently corresponds to the above microstructural examination.…”

Section: Mechanical Properties Of the Diffusion-bonded Mea/dd5 Jointmentioning

confidence: 83%

Microstructure and Mechanical Properties of Diffusion-Bonded CoCrNi-Based Medium-Entropy Alloy to DD5 Single-Crystal Superalloy Joint

Sun

et al. 2021

Crystals

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This study focuses on the diffusion bonding of a CoCrNi-based medium-entropy alloy (MEA) to a DD5 single-crystal superalloy. The microstructure and mechanical properties of the joint diffusion-bonded at variable bonding temperatures were investigated. The formation of diffusion zone, mainly composed of the Ni3(Al, Ti)-type γ′ precipitates and Ni-rich MEA matrix, effectively guaranteed the reliable joining of MEA and DD5 substrates. As the bonding temperature increased, so did the width of the diffusion zone, and the interfacial microvoids significantly closed, representing the enhancement of interface bonding. Both tensile strength and elongation of the joint diffusion-bonded at 1110 °C were superior to those of the joints diffusion-bonded at low temperatures (1020, 1050, and 1080 °C), and the maximum tensile strength and elongation of 1045 MPa and 22.7% were obtained. However, elevated temperature produced an adverse effect that appeared as grain coarsening of the MEA substrate. The ductile fracture of the joint occurred in the MEA substrate (1110 °C), whereas the tensile strength was lower than that of the MEA before diffusion bonding (approximately 1.3 GPa).

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“…A micro‐fatigue testing system was used for the in situ observation of multi‐scale fatigue crack propagation of 304 SS. Details of the test system can be seen in Li et al The stress‐control fatigue tests were performed at room temperature with a sine‐waveform frequency of 1 Hz and stress ratios of 0.1 and 0.5. Three different maximum stresses, σ max , namely 270, 360 and 500 MPa, were applied on the plane with the smallest cross section, that is the middle part of the specimen.…”

Section: Methodsmentioning

confidence: 99%

Multi‐scale fatigue crack propagation in 304 stainless steel: experiments and modelling

Zhang

Gong

et al. 2017

Fatigue Fract Eng Mat Struct

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The stages of fatigue crack initiation and small crack propagation usually occupy most part of fatigue life. The multi‐scale fatigue crack propagation mechanism of 304 stainless steel using in situ optical microscopy was investigated in this paper. An analytical model was also proposed to predict the multi‐scale crack growth rate. Results indicated that grain boundaries inhibit the small crack propagation and lead to the fluctuation of crack growth rate when the applied stress is relatively low. The prediction results using the proposed model agree well with the experimental result. The effect of grain size distribution on crack growth rate can be identified by the present model. Moreover, the prediction capacity of the proposed model is further verified by using another two materials, for example 7075‐T6 and U720Li.

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In situ observation of interfacial fatigue crack growth in diffusion bonded joints of austenitic stainless steel

Cited by 26 publications

References 20 publications

Exploring the fabrication limits of thin-wall structures in a laser powder bed fusion process

Exploring the fabrication limits of thin-wall structures in a laser powder bed fusion process

Microstructure and Mechanical Properties of Diffusion-Bonded CoCrNi-Based Medium-Entropy Alloy to DD5 Single-Crystal Superalloy Joint

Multi‐scale fatigue crack propagation in 304 stainless steel: experiments and modelling

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