Effect of three-stage heat treatment on the composite waveform and variable amplitude fatigue properties of TC4 titanium alloy pulsed laser-arc hybrid welded joints

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue Pub Date : 2024-11-13 DOI:10.1016/j.ijfatigue.2024.108673

Rui Su , Qianli Liu , Haizhou Li , Dirui Wang , Jinquan Guo , Shengbo Li , Wantong Wang , Aixin Feng , Zhongtao Sun , Hui Chen

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Abstract

Titanium alloy welded structures are often subjected to cyclic loading with composite waveform and variable amplitude during actual service, exacerbating the damage to the joints and leading to low fatigue life. Therefore, a three-stage heat treatment was adopted in this work to enhance the fatigue life of TC4 titanium alloy pulsed laser-arc hybrid welded joints, and its microstructure evolution and fracture mechanism were investigated. The results show that the high-density phase boundary formed by the finely dispersed secondary α phase precipitated after heat treatment was the main reason for the increase of life by 3 times. The crack initiation was mainly due to the accumulation of Pyramidal < c + a > dislocations and base < a > dislocations. The difference was that, combined with molecular dynamics calculations and characterization by TEM and EBSD, it was found that the heat-treated cracks underwent dislocation accumulation, deformation twinning, and low-angle grain boundaries before the initiation of the lamellar α-concave position.

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三级热处理对 TC4 钛合金脉冲激光-电弧混合焊接接头的复合波形和变幅疲劳特性的影响

钛合金焊接结构在实际使用过程中经常受到复合波形和变幅的循环加载，加剧了接头的损伤，导致疲劳寿命低。因此，本研究采用了三阶段热处理来提高 TC4 钛合金脉冲激光-电弧混合焊接接头的疲劳寿命，并研究了其微观结构演变和断裂机理。结果表明，热处理后析出的细小分散的二次α相形成的高密度相界是寿命提高 3 倍的主要原因。裂纹的产生主要是由于金字塔位错（Pyramidal < c + a >）和基底位错（base < a >）的积累。不同之处在于，结合分子动力学计算以及 TEM 和 EBSD 表征，发现热处理裂纹在形成片状 α 凹陷位置之前经历了位错积累、变形孪晶和低角度晶界。

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来源期刊

International Journal of Fatigue 工程技术-材料科学：综合

CiteScore

10.70

自引率

21.70%

发文量

619

审稿时长

58 days

期刊介绍： Typical subjects discussed in International Journal of Fatigue address: Novel fatigue testing and characterization methods (new kinds of fatigue tests, critical evaluation of existing methods, in situ measurement of fatigue degradation, non-contact field measurements) Multiaxial fatigue and complex loading effects of materials and structures, exploring state-of-the-art concepts in degradation under cyclic loading Fatigue in the very high cycle regime, including failure mode transitions from surface to subsurface, effects of surface treatment, processing, and loading conditions Modeling (including degradation processes and related driving forces, multiscale/multi-resolution methods, computational hierarchical and concurrent methods for coupled component and material responses, novel methods for notch root analysis, fracture mechanics, damage mechanics, crack growth kinetics, life prediction and durability, and prediction of stochastic fatigue behavior reflecting microstructure and service conditions) Models for early stages of fatigue crack formation and growth that explicitly consider microstructure and relevant materials science aspects Understanding the influence or manufacturing and processing route on fatigue degradation, and embedding this understanding in more predictive schemes for mitigation and design against fatigue Prognosis and damage state awareness (including sensors, monitoring, methodology, interactive control, accelerated methods, data interpretation) Applications of technologies associated with fatigue and their implications for structural integrity and reliability. This includes issues related to design, operation and maintenance, i.e., life cycle engineering Smart materials and structures that can sense and mitigate fatigue degradation Fatigue of devices and structures at small scales, including effects of process route and surfaces/interfaces.