Mechanical properties of low-transformation-temperature weld metals after low-temperature postweld heat treatment

Wu, Shipin; Wang, Dongpo; Zhang, Zhi; Li, Chengning; Liu, Xiuguo; Meng, Xianqun; Feng, Zhongyuan; Di, Xinjie

doi:10.1080/13621718.2018.1492776

Cited by 21 publications

(10 citation statements)

References 35 publications

(44 reference statements)

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“…According to Singh et al [34], ductility (% elongation) of base metal and weld joint was improved after heat treatment, which may be the key reason for the reduction of impact toughness. These results are in contrast with results (for steel) reported by Lu et al [56] and Wu et al [57].…”

Section: Impact Toughnesscontrasting

confidence: 99%

Microstructural and Mechanical Behaviour Evaluation of Mg-Al-Zn Alloy Friction Stir Welded Joint

Singh¹,

Singh²,

Singh³

2020

IJAME

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The weight reduction concept is most effective to reduce the emissions of greenhouse gases from vehicles, which also improves fuel efficiency. Amongst lightweight materials, magnesium alloys are attractive to the automotive sector as a structural material. Welding feasibility of magnesium alloys acts as an influential role in its usage for lightweight prospects. Friction stir welding (FSW) is an appropriate technique as compared to other welding techniques to join magnesium alloys. Field of friction stir welding is emerging in the current scenario. The friction stir welding technique has been selected to weld AZ91 magnesium alloys in the current research work. The microstructure and mechanical characteristics of the produced FSW butt joints have been investigated. Further, the influence of post welding heat treatment (at 260 °C for 1 h) on these properties has also been examined. Post welding heat treatment (PWHT) resulted in the improvement of the grain structure of weld zones which affected the mechanical performance of the joints. After heat treatment, the tensile strength and elongation of the joint increased by 12.6 % and 31.9 % respectively. It is proven that after PWHT, the microhardness of the stir zone reduced and a comparatively smoothened microhardness profile of the FSW joint obtained. No considerable variation in the location of the tensile fracture was witnessed after PWHT. The results show that the impact toughness of the weld joints further decreases after post welding heat treatment.

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Section: Impact Toughnesscontrasting

confidence: 99%

Microstructural and Mechanical Behaviour Evaluation of Mg-Al-Zn Alloy Friction Stir Welded Joint

Singh¹,

Singh²,

Singh³

2020

IJAME

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“…In particular, the proof that compressive residual stresses are formed [3,4], the investigation of the mechanisms of stress formation [5,6], and the effect on the fatigue strength [7,8] have been the subject of many research projects. Recent publications also deal with extended topics such as microstructure and the associated mechanical properties [9][10][11][12][13], the behaviour during multilayer welding [14][15][16][17][18], and the application of LTT in beam welding [19].…”

Section: Ltt Filler Metalsmentioning

confidence: 99%

Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals

et al. 2020

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The subject of this study is how, and to what extent, Varestraint/Transvarestraint test results are influenced by both testing parameters and characteristics of evaluation methods. Several different high-alloyed martensitic LTT (low transformation temperature) filler materials, CrNi and CrMn type, were selected for examination due to their rather distinctive solidification cracking behaviour, which aroused interest after previous studies. First, the effects of different process parameter sets on the solidification cracking response were measured using standard approaches. Subsequently, microfocus X-ray computer tomography (μCT) scans were performed on the specimens. The results consistently show sub-surface cracking to significant yet varying extents. Different primary solidification types were found using wavelength dispersive X-ray (WDX) analysis conducted on filler metals with varying Cr/Ni equivalent ratios. This aspect is regarded as the main difference between the CrNiand CrMn-type materials in matters of cracking characteristics. Results show that when it comes to testing of modern highperformance alloys, one set of standard Varestraint testing parameters might not be equally suitable for all materials. Also, to properly accommodate different solidification types, sub-surface cracking has to be taken into account.

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“…While considering the higher solubility of hydrogen in an austenitic phase, the large fraction of retained austenite (24.6%) at room temperature in the weld metal could reduce dramatically the tendency towards HICC compared with fully martensitic microstructure. In addition, the yield strength of the two phase (martensite and retained austenite microstructure) would be much lower than single phase martensitic microstructure, as reported by Wu et al [33], which is another benefit of a reduced tendency towards HICC. Finally, as the Ms in the weld is low (158.3 °C), the volume expansion induced by phase transformation from austenite to martensite could significantly reduce the tensile residual stress in the weld metal region [34].…”

Section: Discussionmentioning

confidence: 87%

A Combination of Keyhole GTAW with a Trapezoidal Interlayer: A New Insight into Armour Steel Welding

et al. 2019

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The ballistic performance of armour steel welds using austenitic filler materials is poor on account of the disparity in the mechanical properties of the weld and base metals. Consequently, a novel Keyhole Gas Tungsten Arc Welding process with a trapezoidal AISI309 austenitic stainless steel interlayer was developed to tailor chemical composition and microstructure by controlling the solidification sequence. Results show that the dilution rate in the weld metal region can reach up to 43.5% by placing a specially designed interlayer in between the base metal, providing a major scope for microstructure modification. Detailed weld analysis was undertaken by X-ray diffraction, optical and secondary and transmission electron microscopy, energy dispersive spectroscopy and electron back-scattering diffraction. The results from Vickers hardness indents and Charpy impact toughness testing at −40 °C show that the properties of the weld metal region are comparable to that of the base metal. This is ascribed to the weld metal comprising a two phase microstructure of martensite and retained austenite, which contribute to improvements in strength and toughness, respectively. Furthermore, the tailored chemical composition, microstructure and low temperature phase transformation in the weld metal may reduce the tendency toward both solidification cracking and hydrogen assisted cold cracking.

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Mechanical properties of low-transformation-temperature weld metals after low-temperature postweld heat treatment

Cited by 21 publications

References 35 publications

Microstructural and Mechanical Behaviour Evaluation of Mg-Al-Zn Alloy Friction Stir Welded Joint

Microstructural and Mechanical Behaviour Evaluation of Mg-Al-Zn Alloy Friction Stir Welded Joint

Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals

A Combination of Keyhole GTAW with a Trapezoidal Interlayer: A New Insight into Armour Steel Welding

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