Study of Microstructure and Residual Stresses in Dissimilar Al/Steels Welds Produced by Cold Metal Transfer

Recently a new welding technique, the so-called ‘Cold Metal Transfer’ (CMT) technique was introduced, which due to integrated wire feeding leads to lower heat input and higher productivity compared to other gas metal arc (GMA) techniques. Here microstructure formation and residual stress state in dissimilar steel to aluminum CMT welds are investigated. The intermetallic phase seam between the filler and the steel is only a few micrometers thick. Residual stress analyses reveal the formation of the typical residual stress state of a weld without phase transformation. Both in longitudinal and in transversal direction compressive residual stresses exist in the steel plate parent material, tensile residual stresses are present in the heat affected zone of the steel and the aluminum alloy. The area containing tensile residual stresses is larger in the aluminum alloy due to its higher heat conductivity than in the steel. Due to the symmetry in the patented voestalpine welding geometry and the welding from bottom and face side of the weld, the residual stress distributions at the top and at the bottom side of the weld are very similar.

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Dissimilar robotic cold metal transfer (CMT) welding of an aluminum alloy to galvanized steel

Materials Testing ◽

10.3139/120.111287 ◽

2019 ◽

Vol 61 (1) ◽

pp. 91-96

Author(s):

Haldun Numan ◽

Emel Taban

Keyword(s):

Aluminum Alloy ◽

Metal Transfer ◽

Galvanized Steel ◽

Cold Metal Transfer ◽

Cmt Welding ◽

Cold Metal

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Effect of path strategy on residual stress and distortion in laser and cold metal transfer hybrid additive manufacturing

Additive Manufacturing ◽

10.1016/j.addma.2021.102203 ◽

2021 ◽

pp. 102203

Author(s):

Runsheng Li ◽

Guilan Wang ◽

Xushan Zhao ◽

Fusheng Dai ◽

Cheng Huang ◽

...

Keyword(s):

Residual Stress ◽

Additive Manufacturing ◽

Metal Transfer ◽

Cold Metal Transfer ◽

Cold Metal

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About Residual Stress State of Castings: The Case of HPDC Parts and Possible Advantages through Semi-Solid Processes

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.327.272 ◽

2022 ◽

Vol 327 ◽

pp. 272-278

Author(s):

Elisa Fracchia ◽

Federico Simone Gobber ◽

Claudio Mus ◽

Yuji Kobayashi ◽

Mario Rosso

Keyword(s):

Residual Stress ◽

Stress State ◽

Residual Stresses ◽

Casting Process ◽

Ray Method ◽

Premature Failure ◽

Thin Walls ◽

Residual Stress State ◽

Semi Solid ◽

Pressure Die Casting

Nowadays, one of the most crucial focus in the aluminium-foundry sector is the production of high-quality castings. Mainly, High-Pressure Die Casting (HPDC) is broadly adopted, since by this process is possible to realize aluminium castings with thin walls and high specific mechanical properties. On the other hand, this casting process may cause tensile states into the castings, namely residual stresses. Residual stresses may strongly affect the life of the product causing premature failure of the casting. Various methods can assess these tensile states, but the non-destructive X-Ray method is the most commonly adopted. Namely, in this work, the residual stress analysis has been performed through Sinto-Pulstec μ-X360s. Detailed measurements have been done on powertrain components realized in aluminium alloy EN AC 46000 through HPDC processes to understand and prevent dangerous residual stress state into the aluminium castings. Furthermore, a comparison with stresses induced by Rheocasting processes is underway. In fact, it is well known that Semi-Solid metal forming combines the advantages of casting and forging, solving safety and environmental problems and possibly even the residual stress state can be positively affected.

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Comparative Study of Laser-Arc Hybrid Welding for AA6082-T6 Aluminum Alloy with Two Different Arc Modes

Metals ◽

10.3390/met10030407 ◽

2020 ◽

Vol 10 (3) ◽

pp. 407 ◽

Cited By ~ 1

Author(s):

Xiaohui Han ◽

Zhibin Yang ◽

Yin Ma ◽

Chunyuan Shi ◽

Zhibin Xin

Keyword(s):

Aluminum Alloy ◽

Heat Affected Zone ◽

Metal Transfer ◽

Inert Gas ◽

Hybrid Welding ◽

Cold Metal Transfer ◽

Melted Zone ◽

Cold Metal ◽

Fracture Features ◽

Softening Region

The effects of arc modes on laser-arc hybrid welding for AA6082-T6 aluminum alloy were comparatively studied. Two arc modes were employed: pulsed metal inert gas arc and cold metal transfer arc. The results indicated that joints without porosity, undercutting, or other defects were obtained with both laser-pulsed metal inert gas hybrid welding (LPMHW) and laser-cold metal transfer hybrid welding (LCHW). Spatter was reduced, and even disappeared, during the LCHW process. The sizes of equiaxed dendrites and the width of the partially melted zone in the LPMHW joint were larger than those in the LCHW joint. The microhardness in each zone of the LPMHW joint was lower than that of the LCHW joint. The softening region in the heat-affected zone of the LPMHW joint was wider than that of the LCHW joint. The tensile strength of the LCHW joint was higher than that of the LPMHW joint. For the two joints, the fractures all occurred in the softening region in the heat-affected zone, and the fracture morphologies showed ductile fracture features. The dimples in the fractograph of the LCHW joint were deeper than those of the LPMHW joint.

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Modelling shattered rim cracking in railroad wheels

Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit ◽

10.1177/0954409711403671 ◽

2011 ◽

Vol 225 (6) ◽

pp. 593-604

Author(s):

V Sura ◽

S Mahadevan

Keyword(s):

Residual Stress ◽

Stress Intensity Factor ◽

Finite Element ◽

Stress Intensity ◽

Stress State ◽

Intensity Factor ◽

Residual Stresses ◽

Equivalent Stress ◽

Crack Tip ◽

Residual Stress State

Shattered rim cracking, propagation of a subsurface crack parallel to the tread surface, is one of the dominant railroad wheel failure types observed in North America. This crack initiation and propagation life depends on several factors, such as wheel rim thickness, wheel load, residual stresses in the rim, and the size and location of material defects in the rim. This article investigates the effect of the above-mentioned parameters on shattered rim cracking, using finite element analysis and fracture mechanics. This cracking is modelled using a three-dimensional, multiresolution, elastic–plastic finite element model of a railroad wheel. Material defects are modelled as mathematically sharp cracks. Rolling contact loading is simulated by applying the wheel load on the tread surface over a Hertzian contact area. The equivalent stress intensity factor ranges at the subsurface crack tips are estimated using uni-modal stress intensity factors obtained from the finite element analysis and a mixed-mode crack growth model. The residual stress and wheel wear effects are also included in modelling shattered rim cracking. The analysis results show that the sensitive depth below the tread surface for shattered rim cracking ranges from 19.05 to 22.23 mm, which is in good agreement with field observations. The relationship of the equivalent stress intensity factor (Δ K eq) at the crack tip to the load magnitude is observed to be approximately linear. The analysis results show that the equivalent stress intensity factor (Δ K eq) at the crack tip depends significantly on the residual stress state in the wheel. Consideration of as-manufactured residual stresses decreases the Δ K eq at the crack tip by about 40 per cent compared to that of no residual stress state, whereas consideration of service-induced residual stresses increases the Δ K eq at the crack tip by about 50 per cent compared to that of as-manufactured residual stress state. In summary, the methodology developed in this article can help to predict whether a shattered rim crack will propagate for a given set of parameters, such as load magnitude, rim thickness, crack size, crack location, and residual stress state.

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Influence of Cooling Intensity on Residual Stress State of TIG Dressing Zone for T-Joint Welded Toe

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.148-149.1289 ◽

2011 ◽

Vol 148-149 ◽

pp. 1289-1294 ◽

Cited By ~ 1

Author(s):

Kun Zhou ◽

Chun Yuan Shi ◽

Cheng Jin

Keyword(s):

Finite Element Method ◽

Residual Stress ◽

Finite Element ◽

Stress State ◽

Residual Stresses ◽

Residual Stress Distribution ◽

Residual Stress State ◽

Cooling Intensity ◽

Stress Layer ◽

Spray Treatment

Using finite element method, the residual stress distribution of the TIG dressed welded toe followed by spray treatment with different cooling intensity was calculated. And the residual stresses of welded toe were also measured by using the blind-hole method. The results indicate that with the increase of cooling intensity, the longitudinal residual stresses in welded toe are gradually transited from tensile residual stresses to compressive ones, and there is no significant change for transverse residual stresses, and the depth of compressive stress layer increases at the welded toe region.

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MICRO-SCALE STUDY OF RESIDUAL STRESSES IN CR2O3 COATINGS SPRAYED BY APS

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2020.27.0042 ◽

2020 ◽

Vol 27 ◽

pp. 42-47

Author(s):

Franck Decroos ◽

Cécile Langlade ◽

Eric Bourillot ◽

Geoffrey Darut ◽

Manuel Francois

Keyword(s):

Residual Stress ◽

Stress State ◽

Residual Stresses ◽

Atmospheric Plasma ◽

Forming Process ◽

Characterization Methods ◽

Residual Stress State ◽

Microwave Microscopy ◽

Early Failures ◽

Material Forming

Whichever the application field, every material forming process generates residual stresses on the surface. While they are likely to enhance the aimed properties of the final mechanical part, these stresses may also drastically reduce them and result in early failures. Therefore, understanding the residual stress state remains a major challenge when coating complex parts, especially as most characterization methods at the microscopic scale involve specific sample preparation procedures which may affect the residual stresses field. This work investigates the residual stress state that exists in chromium oxide coatings deposited via Atmospheric Plasma Spray (APS), using two pioneering techniques featuring high spatial resolution: Scanning Microwave Microscopy and Raman Micro-Spectroscopy. The first technique combines the measurement of microwave electromagnetic capacities of a Vector Network Analyzer with the subnanometric resolution of an Atomic Force Microscope: it thus enables performing depth investigations at very accurately defined positions of the probe on the surface. The second technique relies on the principle of photons inelastic scattering and involves a laser beam aiming at the material sample: it allows a fine characterization of the microstructure as well as defects and stresses detection via molecular vibratory signatures. The investigation scale is limited here to a few cubic micrometers. Due to the highly localized scales of our investigations, which also depend on the device, the objective of our procedure required that the comparison should be made not on individual points but on definite mapped areas, every spot being analyzed and post-treated one after another, with optimum measuring parameters. Results have been correlated with XRD measurements to cross-check the average amount of stress observed over a wider area.

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