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19 pages, 13875 KiB

Open AccessFeature PaperArticle

Residual Stress Reduction with the LTT Effect in Low Carbon Manganese-Steel through Chemical Composition Manipulation Using Dissimilar Filler Material in Laser Beam Welding

by Fatma Akyel, Maximilian Gamerdinger, Simon Olschok, Uwe Reisgen, Alexander Schwedt and Joachim Mayer

Metals 2022, 12(6), 911; https://doi.org/10.3390/met12060911 - 26 May 2022

Cited by 4 | Viewed by 1822

Abstract

This paper investigates the manipulation of chemical composition of a laser weld by dissimilar filler material and its effect on residual stress. The aim is to minimize residual stresses in the weld seam. In order to negate residual stresses, dissimilar combinations of low-carbon [...] Read more.

This paper investigates the manipulation of chemical composition of a laser weld by dissimilar filler material and its effect on residual stress. The aim is to minimize residual stresses in the weld seam. In order to negate residual stresses, dissimilar combinations of low-carbon manganese steel (S235JR) base material with high-alloyed solid filler wires (G19 9 and G25 20), as well as similar combinations with low-alloyed solid filler wire G3Si1 are analyzed. The goal of the paper is to show that the so-called low-transformation-temperature effect can be used to induce residual compressive stresses in a weld without the use of specially manufactured filler wires. Chemical compositions are generated within a laser-beam-welding process by means of dilution, proving that the concept of in situ alloying is usable in order to affect the martensite formation on a weld. Dilatometry measurements show that a varying Cr and Ni content in a weld reduces the phase-transformation temperature and increases dilatation. EBSD analysis indicates that a fully martensitic weld with a negligible amount of retained austenite is created while the base material preserves its ferritic-pearlitic microstructure. Residual stress measurements with the hole-drilling method demonstrate a reduction in longitudinal tensile residual stresses, whereby the magnitude of the induced residual compressive stresses depend on the M_s temperature. As a result of this research, it was proven that a reduction in tensile residual stress by means of targeted alloying with conventional materials in low-carbon manganese steel is possible. Under the experimental conditions, residual stress in the weld seam could be reduced to 0 MPa. In some cases, even compressive residual stress in the weld could be achieved. Full article

(This article belongs to the Special Issue Experimental, Modeling, Simulation and Optimization of Laser Processing in Metallic Materials)

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9 pages, 3101 KiB

Open AccessFeature PaperArticle

Lift-Off Ablation of Metal Thin Films for Micropatterning Using Ultrashort Laser Pulses

by Byunggi Kim, Han-Ku Nam, Young-Jin Kim and Seung-Woo Kim

Metals 2021, 11(10), 1586; https://doi.org/10.3390/met11101586 - 5 Oct 2021

Cited by 1 | Viewed by 2249

Abstract

Laser ablation of metal thin films draws attention as a fast means of clean micropatterning. In this study, we attempt to remove only the metal thin film layer selectively without leaving thermal damage on the underneath substrate. Specifically, our single-pulse ablation experiment followed [...] Read more.

Laser ablation of metal thin films draws attention as a fast means of clean micropatterning. In this study, we attempt to remove only the metal thin film layer selectively without leaving thermal damage on the underneath substrate. Specifically, our single-pulse ablation experiment followed by two-temperature analysis explains that selective ablation can be achieved for gold (Au) films of 50–100 nm thickness by the lift-off process induced as a result of vaporization of the titanium (Ti) interlayer with a strong electron–phonon coupling. With increasing the film thickness comparable to the mean free path of electrons (100 nm), the pulse duration has to be taken shorter than 10 ps, as high-temperature electrons generated by the ultrashort pulses transfer heat to the Ti interlayer. We verify the lift-off ablation by implementing millimeters-scale micropatterning of optoelectronic devices without degradation of optical properties. Full article

(This article belongs to the Special Issue Experimental, Modeling, Simulation and Optimization of Laser Processing in Metallic Materials)

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14 pages, 13021 KiB

Open AccessArticle

The Effect of Plume Generated on the Microstructural Behavior of the Weld Mixed Zone in High-Speed Laser Dissimilar Welding

by Su-Jin Lee, Seiji Katayama, Jong-Do Kim and Jeong Suh

Metals 2021, 11(10), 1556; https://doi.org/10.3390/met11101556 - 29 Sep 2021

Cited by 2 | Viewed by 1948

Abstract

Dissimilar laser welding has been researched to combine the excellent anticorrosion and high strength properties of Ti and the low weight and cost of Al. However, when welding dissimilar Al and Ti sheets, many kinds of intermetallic compound are easily generated. Therefore, intermetallic [...] Read more.

Dissimilar laser welding has been researched to combine the excellent anticorrosion and high strength properties of Ti and the low weight and cost of Al. However, when welding dissimilar Al and Ti sheets, many kinds of intermetallic compound are easily generated. Therefore, intermetallic compounds and differences in material properties make joining such dissimilar metals very difficult. Previous studies clarified that ultra-high welding speed could suppress the weld defects. To elucidate the mechanism of Al and Ti dissimilar laser welding, material behavior of the weld fusion zone and components of fume generated during the ultra-high speed welding process were observed and analyzed using energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high speed cameras, and a spectrometer. The results show that the atom movement of Al and Ti in the weld plume affects the behavior of elemental components distributed in the weld fusion zone. Full article

(This article belongs to the Special Issue Experimental, Modeling, Simulation and Optimization of Laser Processing in Metallic Materials)

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17 pages, 5573 KiB

Open AccessArticle

FE Analysis of Laser Shock Peening on STS304 and the Effect of Static Damping on the Solution

by Ryoonhan Kim, Jeong Suh, Dongsig Shin, Kwang-Hyeon Lee, Seung-Hoon Bae, Dae-Won Cho and Won-Geun Yi

Metals 2021, 11(10), 1516; https://doi.org/10.3390/met11101516 - 24 Sep 2021

Cited by 6 | Viewed by 2105

Abstract

Laser shock peening creates compressive residual stress on the surface of the material, reducing stress corrosion cracking and increasing fatigue life. FE simulation of laser shock peening is an effective way to determine the mechanical effects on the material. In conventional FE simulations [...] Read more.

Laser shock peening creates compressive residual stress on the surface of the material, reducing stress corrosion cracking and increasing fatigue life. FE simulation of laser shock peening is an effective way to determine the mechanical effects on the material. In conventional FE simulations of laser shock peening, explicit analysis is used while pressure loads are applied and switched into implicit analysis to dissipate kinetic energy. In this study, static damping was adopted to dissipate kinetic energy without conversion into implicit analysis. Simulation of a single laser shock and multiple shocks was performed, and deformation and minimum principal stress were compared to evaluate the static damping effect. The history of the internal and kinetic energy were analyzed to compare the stabilization time depending on the damping value. Laser shock peening experiments were also performed on stainless steel 304 material. The residual stress of the specimen was measured by the hole drilling method and it was compared to the FE simulation result. The residual stress from the experiment and the simulation results showed similar distributions in the depth direction. Anisotropic residual stress distribution due to the laser path was observed in both results. Full article

(This article belongs to the Special Issue Experimental, Modeling, Simulation and Optimization of Laser Processing in Metallic Materials)

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14 pages, 4177 KiB

Open AccessFeature PaperArticle

Arc Plasma Flow Variation by Obstruction Structures between Anode and Cathode

by Young-Tae Cho, Gwang-Ho Jeong, Chan-Kyu Kim, Won-Pyo Kim and Young-Cheol Jeong

Metals 2021, 11(9), 1416; https://doi.org/10.3390/met11091416 - 7 Sep 2021

Cited by 3 | Viewed by 2190

Abstract

Arc plasma flow between electrodes has been investigated in several studies. However, in the industrial field, arc plasma flow between electrodes is hindered by interfering materials such as filler metal in arc welding, substrates in chemical vapor deposition, and powders in sintering. Therefore, [...] Read more.

Arc plasma flow between electrodes has been investigated in several studies. However, in the industrial field, arc plasma flow between electrodes is hindered by interfering materials such as filler metal in arc welding, substrates in chemical vapor deposition, and powders in sintering. Therefore, in this study, high temperature arc plasma flow analysis via three obstruction structure shapes was performed to understand the inter-electrode interference phenomena. COMSOL Multiphysics was used for the analysis; COMSOL interface such as electric field, magnetic field, heat transfer, and fluid flow (laminar flow) was applied and Multiphysics such as plasma heat source and temperature coupling were considered. The temperature and velocity of the arc plasma were determined and the energy transfer between the electrodes was analyzed. We confirmed that the concave shape has a lower average heat flux than the other shapes, with the arc pressure evenly distributed in the anode. It is concluded that the concave shape can reduce the flow of the plasma from the anode and obtain even distribution of the arc plasma in the radial direction. Full article

(This article belongs to the Special Issue Experimental, Modeling, Simulation and Optimization of Laser Processing in Metallic Materials)

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17 pages, 33027 KiB

Open AccessArticle

Study on Microstructure and In Situ Tensile Deformation Behavior of Fe-25Mn-xAl-8Ni-C Alloy Prepared by Vacuum Arc Melting

by Yaping Bai, Meng Li, Chao Cheng, Jianping Li, Yongchun Guo and Zhong Yang

Metals 2021, 11(5), 814; https://doi.org/10.3390/met11050814 - 17 May 2021

Cited by 4 | Viewed by 1800

Abstract

In this study, Fe-25Mn-xAl-8Ni-C alloys (x = 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%) were prepared by a vacuum arc melting method, and the microstructure of this series of alloys and the in situ tensile deformation behavior were studied. The [...] Read more.

In this study, Fe-25Mn-xAl-8Ni-C alloys (x = 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%) were prepared by a vacuum arc melting method, and the microstructure of this series of alloys and the in situ tensile deformation behavior were studied. The results showed that Fe-25Mn-xAl-8Ni-C alloys mainly contained austenite phase with a small amount of NiAl compound. With the content of Al increasing, the amount of austenite decreased while the amount of NiAl compound increased. When the Al content increased to 12 wt.%, the interface between austenite and NiAl compound and austenitic internal started to precipitate k-carbide phase. In situ tensile results also showed that as the content of Al increased, the alloy elongation decreased gradually, and the tensile strength first increased and then decreased. When the Al content was up to 11 wt.%, the elongation and tensile strength were 2.6% and 702.5 MPa, respectively; the results of in situ tensile dynamic observations show that during the process of stretching, austenite deformed first, and crack initiation mainly occurred at the interface between austenite and NiAl compound, and propagated along the interface, resulting in fracture of the alloy. Full article

(This article belongs to the Special Issue Experimental, Modeling, Simulation and Optimization of Laser Processing in Metallic Materials)

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11 pages, 6385 KiB

Open AccessArticle

Underwater Laser Welding of Pure Ti: Oxidation and Hardening Behaviors

by Manlelan Luo, Pengyu Wei, Quanhong Li, Renzhi Hu, Anguo Huang and Shengyong Pang

Metals 2021, 11(4), 610; https://doi.org/10.3390/met11040610 - 9 Apr 2021

Cited by 7 | Viewed by 3331

Abstract

The local dry underwater laser welding of cp-Ti, with air as an assisting gas, and in a simulated underwater facility was researched, aiming to find a viable and economical method for repairing titanium alloy underwater vehicles in situ in the future. Macro-morphology, microstructure, [...] Read more.

The local dry underwater laser welding of cp-Ti, with air as an assisting gas, and in a simulated underwater facility was researched, aiming to find a viable and economical method for repairing titanium alloy underwater vehicles in situ in the future. Macro-morphology, microstructure, and microhardness of the cp-Ti laser welds, as a function of welding parameters, were experimentally characterized. The oxidation and hardening behaviors of the welds were also studied in detail. It was found that local dry underwater laser welding with air assisted blowing is feasible for obtaining a complete and glossy weld. Compared with a weld in atmosphere, the cross-section morphology of the weld was almost unaffected by the special underwater welding environment. The weld presented a three-layer structure. High temperature and high pressure water vapor and local blowing are the direct causes of weld oxidation, and porosity defects further aggravate the oxidation behavior. The oxygen-enriched areas were mostly concentrated in the top area of the weld center and near the fusion zone, because of the higher number of grain boundaries and phase boundaries. In addition, the partial oxidation caused by local blowing and water vapor atmosphere, and also the higher strength acicular martensite caused by the rapid cooling effect of water, will lead to weld hardening. However, adjusting the welding process parameters, such as increasing the welding speed, can effectively reduce the microhardness of the weld. Our findings can provide an understanding of the influence of water environment on underwater laser welding, and verify the feasibility of a more economical method for the in situ repair of large underwater facilities. Full article

(This article belongs to the Special Issue Experimental, Modeling, Simulation and Optimization of Laser Processing in Metallic Materials)

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Review

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15 pages, 2555 KiB

Open AccessReview

Innovations in Monitoring, Control and Design of Laser and Laser-Arc Hybrid Welding Processes

by Zheng-Xiong Ma, Pei-Xin Cheng, Jie Ning, Lin-Jie Zhang and Suck-Joo Na

Metals 2021, 11(12), 1910; https://doi.org/10.3390/met11121910 - 26 Nov 2021

Cited by 6 | Viewed by 3140

Abstract

With the rapid development of high power laser, laser welding has been widely used in many fields including manufacturing, metallurgy, automobile, biomedicine, electronics, aerospace etc. Because of its outstanding advantages, such as high energy density, small weld size, easy automation. Combining the two [...] Read more.

With the rapid development of high power laser, laser welding has been widely used in many fields including manufacturing, metallurgy, automobile, biomedicine, electronics, aerospace etc. Because of its outstanding advantages, such as high energy density, small weld size, easy automation. Combining the two heat sources of laser and arc for welding can achieve excellent results due to the synergistic effect. Laser welding is a complicated physical and chemical metallurgical process, involving the laser beam and molten pool, keyholes and materials melting, evaporation and multiple physical process. Process monitoring and quality control are important content of research and development in the field of laser welding, which is the premise to obtain fine weld with high quality. Numerical simulation technology can describe many complex physical phenomena in welding process, which is very important to predict weld forming and quality and clarify the underline mechanism. In this paper, the research progress of process monitoring, quality control and autonomous intelligent design of laser and laser-arc hybrid welding based on numerical simulation were reviewed, and the research hotspots and development trends of laser welding in the future are predicted. Full article

(This article belongs to the Special Issue Experimental, Modeling, Simulation and Optimization of Laser Processing in Metallic Materials)

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