Welding Metallurgy of
01 Jan 1987-
About: The article was published on 1987-01-01 and is currently open access. It has received 991 citations till now. The article focuses on the topics: Welding.
Citations
More filters
TL;DR: In this paper, microstructural development, post-weld ageing response and mechanical properties of gas tungsten arc and CO2 laser welded Al-6 %Cu (AA2219) alloy were investigated.
Abstract: Microstructural development, post-weld ageing response and mechanical properties of gas tungsten arc and CO2 laser welded Al-6 %Cu (AA2219) alloy were investigated in the present study. The fusion zone of laser weld consists of three parts: the fine grains in the middle part, the columnar zone and equiaxed zone adjacent to fusion boundary. In contrast, fusion zone of gas tungsten arc weld consists of two parts: the columnar zone in the middle part and the equiaxed zone adjacent to fusion boundary. The size of the equiaxed grains in the fusion zone was the least in the laser welds when compared to gas tungsten arc welds. Laser welds have exhibited higher hardness, post weld ageing response, yield strength, ductility and fatigue strength when compared with gas tungsten arc welds. Fine equiaxed grain morphology and discontinues eutectic distribution in the laser weld fusion zone could be attributed to the improved tensile and fatigue properties of laser welded samples. ‘Thermal pinning effect’, due ...
5 citations
TL;DR: In this paper, the thermodynamic calculations of the complex process of the water decomposition under the conditions of high electric arc temperatures at a pressure of 1 1/m of steam are discussed.
Abstract: The pore and crack formations in the weld bead during underwater wet welding are the main cause of failure to reach the required mechanical properties of the weld metal. These defects are closely associated with the decomposition of the water molecule under electric arc conditions. In this paper, the thermodynamic calculations of the complex process of the water decomposition under the conditions of high electric arc temperatures at a pressure of 1 atm of steam are discussed. The values of the partial pressures of the five main products of the vaporizations and decomposition of the water (H2O(g), H2, O2, H and O) are calculated for temperatures between 1870 and 4000 K. Due to the fact that atomic hydrogen is mainly responsible for pore formation in the weld metal, its partial pressure as a function of partial pressures of atomic oxygen and steam (water vapour) is expressed. Hydrogen solubility values in the liquid metal under the conditions of underwater wet welding at depths of 50 and 100 m, and a compar...
5 citations
TL;DR: In this paper, a method for predicting solidification cracking during laser welding by accurately obtaining the high temperature ductility and weld strain of weld metal was developed, where the U-type hot cracking behavior was in-situ observed by a high speed camera so that the critical strain for the initiation of solidification crack was measured precisely.
Abstract: This study is purposed to develop a systematic method for prediction of solidification cracking during laser welding by accurately obtaining the high temperature ductility and weld strain of weld metal. The U-type hot cracking test was carried out under various initial loads; solidification cracking behavior was in-situ observed by a high speed camera so that the critical strain, for the initiation of solidification crack, was measured precisely. With the critical strain and temperature history measured at the solidification crack, the high temperature ductility curve was achieved. Meanwhile, a three dimensional FEM-analysis was performed to obtain the detailed strain history at the crack initiation point during laser welding. In order to get the accurate strain history, it is necessary to obtain the accurate material properties of weld metal at the elevated temperature up to solidification temperature range. The FEM-analysis was carried out by using the obtained high temperature material properties, which were measured by a developed high temperature tensile test with in-situ observation. Therefore, it became possible to predict the occurrence of solidification cracking during laser welding accurately by using both of the detailed high temperature ductility curve measured experimentally and the strain history obtained by the 3D FEM-analysis.
5 citations
TL;DR: In this paper , the authors compared the properties of three groups of as-built nitinol (NiTi) samples fabricated using three pre-determined volumetric energy densities (VED) as calculated based on hatch spacings ( VED H = 40, 80, and 120 J/mm 3 ).
Abstract: In this study, direct comparisons between the properties of three groups of as-built nitinol (NiTi) samples fabricated using three pre-determined volumetric energy densities (VED) as calculated based on hatch spacings ( VED H = 40, 80, and 120 J/mm 3 ), were examined. The additive manufacturing technique adopted is the powder bed fusion using a laser beam (PBF-LB), and the powder feedstock is Ni 50 Ti 50 . Although the three VED H ' s increased by 100% for each sample group, each VED H value was within the range of those recommended in the literature, as well as equivalent to 100 J/mm 3 ( VED f ), VED as calculated based on laser spot size. Significant differences were found between the thermal profiles and normalised thermal gradients, resulting in compositional differences, defects, phase, and phase transformation behaviour, Young's modulus, hardness, and microstructure. Thermal gradients and full-wave amplitude of the in-situ melt pool thermal radiation waveforms increased as VED H increased. Higher VED H 's resulted in more martensitic NiTi samples with larger melt pool volume and >98% sample relative density. Austenite transformation temperatures increased with an increase in at.% Ti for each increase in VED H , consequent on the higher normalised average melt pool temperatures. The calculated thermal gradient (normalised) was correlated to higher thermal stresses as VED H increased, resulting in residual stress-induced weld-metal liquation microcracks. This work has demonstrated the potential of post-processed in-situ melt pool thermal radiation data, in providing insights into the physical property variations of as-built nitinol samples fabricated via PBF-LB.
5 citations
01 Jan 2010
TL;DR: In this article, the mechanical properties of austentic stainless steel for the process of TIG and MIG welding are discussed. And the voltage is taken constant and various characteristics such as strength, hardness, ductility, grain structure, modulus of elasticity, tensile strength breaking point, HAZ are observed in two processes and analyzed and finally concluded.
Abstract: In this Paper we discuss about the mechanical properties of austentic stainless steel for the process of TIG and MIG welding. As with other welding processes such as gas metal arc welding, shielding gases are necessary in GTAW or MIG welding is used to protect the welding area from atmospheric gases such as nitrogen and oxygen, which can cause fusion defects, porosity, and weld metal embrittlement if they come in contact with the electrode, the arc, or the welding metal. The gas also transfers heat from the tungsten electrode to the metal, and it helps start and maintain a stable arc. We used the TIG and MIG process to find out the characteristics of the metal after it is welded .The voltage is taken constant and various characteristics such as strength, hardness, ductility, grain structure, modulus of elasticity, tensile strength breaking point, HAZ are observed in two processes and analyzed and finally concluded.
5 citations
References
More filters
TL;DR: In this article, the state of the art in selective laser sintering/melting (SLS/SLM) processing of aluminium powders is reviewed from different perspectives, including powder metallurgy (P/M), pulsed electric current (PECS), and laser welding of aluminium alloys.
1,172 citations
TL;DR: In this article, the authors show that the pre-existing dislocation network, which maintains its configuration during the entire plastic deformation, is an ideal modulator that is able to slow down but not entirely block the dislocation motion.
557 citations
TL;DR: In this article, the fundamental understanding of structure-properties relationship in automotive steels resistance spot welds is discussed. And a brief review of friction stir spot welding, as an alternative to RSW, is also included.
Abstract: Spot welding, particularly resistance spot welding (RSW), is a critical joining process in automotive industry. The development of advanced high strength steels for applications in automotive industry is accompanied with a challenge to better understand the physical and mechanical metallurgy of these materials during RSW. The present paper critically reviews the fundamental understanding of structure–properties relationship in automotive steels resistance spot welds. The focus is on the metallurgical characteristics, hardness–microstructure correlation, interfacial to pullout failure mode transition and mechanical performance of steel resistance spot welds under quasi-static, fatigue and impact loading conditions. A brief review of friction stir spot welding, as an alternative to RSW, is also included.
369 citations
TL;DR: In this article, a unified equation to compute the energy density is proposed to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.
369 citations
TL;DR: This study attempted to predict solidification defects by DNN regression with a small dataset that contains 487 data points and found that a pre-trained and fine-tuned DNN shows better generalization performance over shallow neural network, support vector machine, and DNN trained by conventional methods.
314 citations