Microstructural evolution in CoCrFeNi and CoCrCuFeNi alloys processed by autogenous fusion welding

The aim herein is to study the microstructural and mechanical changes generated in a welded joint of Ti‐containing twinning‐induced plasticity (TWIP) steel by the gas tungsten arc welding (GTAW) process. For this purpose, the welding parameters that allow the union of 5.6 mm‐thick butt plates with full penetration and without filler material are investigated. Microstructural changes are examined by light optical metallography. Segregation and second‐phase precipitated particles are investigated by scanning electron microscopy and electron‐dispersive spectroscopy. Phase transformations are evaluated using X‐ray diffraction. Finally, the mechanical behavior is assessed by Vickers microhardness and microtensile tests. In general, the welded joint shows dendritic structure formations in the fusion zone (FZ) and equiaxed grain growth in the heat‐affected zone (HAZ). The FZ shows a high degree of segregation, where Mn, Si, and C segregate in the interdendritic regions, whereas Al preferentially segregates in dendritic areas. In contrast, no effect on austenite stability is noticed. The welded joint shows an increase in microhardness, which is associated with the formation of precipitated particles. Finally, the microtensile results show a decrease in ultimate tensile strength (UTS) in the FZ, whereas the welding interface and HAZ show an increase in UTS compared with the base material.

In this work, laser welding of CoCrFeNi and CoCrCuFeNi HEA was carried out. X-ray diffraction, electron backscattered diffraction, mechanical property and microstructural analyses were performed. In CoCrFeNi alloy, a face centred cubic (FCC) structure was observed in both base metal and laser-welded conditions. The addition of Cu in CoCrFeNi alloy is resulted in two FCC phases and has increased the tensile strength from 593 to 666 MPa. The fusion zone of both the welds shows coarser columnar grain and lower hardness compared to that of base metals. Post-welding results show 53% decrease in tensile strength in the alloy containing Cu (CoCrFeNiCu). Whereas only a marginal decrease in strength is observed in CoCrFeNi alloy.

This experimental study investigates the effects of welding low nickel Cr-Mn austenitic stainless steel with gas tungsten arc welding process with and without filler (autogenous) weld by varying the welding currents (120A, 130A and 140A). The microstructural examination of weld has been carried out with optical microscope and mechanical properties with Vickers microhardness and tensile tester. The corrosion behaviour of the welded joints are analysed by double loop electrochemical potentio-kinetic reactivation test to obtain degree of sensitisation. The microstructural examination of welded joints revealed that, as the welding current increases, the inter-dendritic spacing as well as the dendrite size increases. The tensile strength and hardness decrease with increasing welding current for 308 L filler and autogenous weld. The degree of sensitisation increases with increasing welding current for both the welds. The results reveal that the autogenous welds have higher tensile strength, higher hardness and lower degree of sensitisation as compared to welds with 308 L filler.

Martensitic steels have been successfully employed in resource-based industries where components must endure aggressive conditions. In industrial practice, many parts of these components are joined by welding techniques. The aim of this work was to understand the influence of welding on the wear resistance of quenched and tempered carbon martensitic steel subjected to dry linear reciprocating sliding micro-wear tests. Weld-joints were produced using autogenous Gas Tungsten Arc Welding process (GTAW). Micro-wear tests were performed at base metal (BM), weld metal (WM), coarse grained heat affected zone (CG-HAZ) and lowest hardness region of heat affected zone (LHR-HAZ). LHR-HAZ was softened during welding process so plastic deformation was facilitated, and consequently adhesion, material displacement and micro-ploughing. WM and CG-HAZ presented a similar martensitic structure, which explain the similarities found on wear behavior. These regions presented the lowest worn volume average values (w). It was interesting to note that despite its highest microhardness value, the highest w was observed for BM. For some BM samples, debris had a key role promoting material loss by micro-cutting which causes great extent of material removal compared to other micro-wear mechanisms as micro-ploughing and adhesion. Due to debris action BM also presented a great dispersion in w results. The results suggest that material loss of welded joint and BM was strongly controlled by micro-wear mechanisms.

This study examines procedures for consistently producing sound (crack and void free) welds using the autogenous (without filler metal) gas tungsten arc (GTA) welding process. Cast alloy Ti-48Al-2Cr-2Nb (at. pct) and extruded alloy Ti-46Al-2Cr-2Nb-0.9Mo (at. pct) have been examined to determine if sound welds can be produced using autogenous GTA welding without any preheat. Experimentation consisted of GTA spot welding samples of gamma titanium aluminide at weld current levels of 45, 55, 65, and 75 A for a duration of 3 seconds. For the cast alloy, current levels of 45, 55, and 65 A for 3 seconds produced similar fusion zone microstructures, which consisted of a dendritic solidification structure. The fusion zone microstructure of the 75 A for 3 seconds current level differed significantly from the lower current levels. It also consisted of a dendritic solidification structure; however, the morphology was quite different. For the extruded alloy, current levels of 45 and 55 A for 3 seconds produced fusion zone microstructures similar to the lower current level samples of the cast γ-TiAl, which consisted of a dendritic solidification structure. The fusion zone microstructures of the 65 and 75 A samples were similar to each other, but they had a dendritic solidification structure of a different morphology than that of the 45 and 55 A samples. For both alloys at all current levels, microhardness profiles showed an increase in hardness from the base metal to the fusion zone. There were no significant differences in the average fusion zone hardness as a function of increasing current level. However, nanoindentation testing did show that certain phases and microconstituents in the fusion zone did have significant variations in hardness in relation to the enrichment and depletion of chromium.

Ferritic stainless steels of the 400 series have been available for automotive exhaust system, heat exchanger, radiater etc. in various industrial because heat resistance, corrosion resistance and strength are excellent. Especially, automotive exhaust system is required good heat resistance because typical temperature of exhaust system exposed during operation of engine is reach up to . However, research for effect of high temperature in ferritic stainless steels is not enough. In this study, high temperature tensile properties of lap weld of ferritic stainless steels(STS 429) were investigated. In accordance with heat input, lap welds had been produced and were evaluated at high temperature() to compare high temperature tensile properties. In addition, room temperature tensile tests were carried out for non-aging and aging specimens. As a result of R.T tensile test, non-aging specimens were fractured in base metal except for low heat input specimen and aging specimens were fractured in weld metal. Also high temperature tensile test were carried out by aging specimen. After high temperature tensile test, fracture of aged specimen was occurred in base metal except for low heat input specimen. Fracture surface of low heat input specimen in weld metal was confirmed as brittle fracture with observation using scanning electron microscope(SEM). Significant decrease in ultimate tensile strength (between 82 and 85%) was observed for aged ferritic stainless steels(STS 429) when tested at high temperature.

This work was performed to characterize the dissimilar austenitic grade SS304 L and martensitic grade creep strength of an enhanced P92 steel welded joint. The welded joint was prepared using the autogenous gas tungsten arc welding process. The welded joint was subjected to conventional heat treatment consisting of tempering at 760 °C for 2 hours, followed by air cooling and unconventional heat treatment (UHT) consisting of normalizing (1040 °C/40 min), further followed by air cooling and, finally, stabilized tempering at 760 °C for 2 hours. The heat-treated welded joint was subjected to the microstructural characterization and mechanical testing. The room temperature Charpy toughness (CT) testing for both the weld fusion zone (WFZ) and heat-affected zone, tensile testing, and hardness testing were performed to characterize the dissimilar welded joint. Stabilized microstructure associated with improved mechanical properties were observed for UHT. The CT and tensile strength were optimum for the UHT.

The use of low‐density (LD) steels has become increasingly important due to the advantages they offer, such as high strength, high ductility, and principally weight reduction. However, there are few studies regarding their weldability by conventional processes due to the metallurgical complexity of these alloys, including kappa carbides precipitation and hot‐cracking associated with the high contents of Mn, Al, and C. Herein, the main objective is the characterization of the fusion zone and different heat‐affected zones of austenitic Fe–Mn–Al–C LD steels microalloyed with Ti/B and Ce/La. For this purpose, weld nuggets were prepared by autogenous gas tungsten arc welding process using heat inputs of 660 and 975 J. The weld nuggets were characterized metallographic, structural, and mechanically by light optical microscopy, scanning electron microscopy, X‐ray diffraction, and Vickers microhardness. In general, weld nuggets shows three well‐defined zones where γ‐austenite is the main phase and AlN and MnS particles act as nuclei of complex precipitated particles of microalloying elements such as TiC and (Ce, La)O. A considerable decrease in hot‐cracking was noticed in the microalloyed grades. A modulated structure of kappa‐carbide particles was responsible of the largest hardness values (≈450 Vickers microhardness) in the second heat‐affected zone.

Dissimilar weldments of AISI 316 and Monel 400 are extensively used in boiler feed water heaters where the weld roots are exposed to high pressure and hot corrosive environments. In this research, metallurgical and mechanical properties of dissimilar weldments of AISI 316 and Monel 400 obtained by pulsed current gas tungsten arc welding (PCGTAW) and constant current gas tungsten arc welding (CCGTAW) processes were compared. The heat input rate and filler wire were same in both welding techniques. Metallurgical properties are studied by employing optical microscope (OM) and scanning electron microscope (SEM). Mechanical properties of dissimilar weldments are determined by tension test and Vickers hardness. The metallurgical study has revealed fine grain structures with clear grain boundaries at the heat-affected zone in PCGTAW weldment. The ultimate tensile strength in PCGTAW and CCGTAW weldments was observed as 554 and 542 MPa, respectively. The ratio of yield strength to ultimate tensile strength is higher in PCGTAW weldment than CCGTAW weldment. The weldment developed by using PCGTAW technique has shown a higher microhardness value at HAZ of both the base metals than the weldment developed in CCGTAW technique.

An extensive analysis of GTAW process and its influence on the microstructure and mechanical properties of SDSS 2507

Study on effect of grain refinement of P92 steel base plate on mechanical and microstructural features of the welded joint

Physical and mechanical modeling of the neutron irradiation effect on ductile fracture. Part 2. Prediction of swelling effect on drastic decrease in strength

Tensile mechanical properties of glass fiber reinforcement polymer (GFRP) bars under temperature effect is very important for engineering application. Based on three types of GFRP bars with different diameters under elevated and low temperature, change law of ultimate tensile strength and tensile elastic modulus in the temperature range of -20 °C to 300 °C were studied on GFRP bars. The results show that ultimate tensile strength decreases with the rise of temperature from -20 °C to 300 °C. Ultimate tensile strength and tensile elastic modulus decrease linearly below 100 °C. Above 100 °C, ultimate tensile strength decreases faster, temperature is higher. These

The mechanical behavior of the uranium-3/4 weight percent titanium alloy in the aged condition has been characterized by tension, notched tension, and compression tests. These tests were made over a temperature range of {minus}196{degree}C to 80{degree}C, at strain rates from .001 s{sup {minus}1} to 2000 s{sup {minus}1}. Metallography on selected samples using optical and scanning electron microscopes was used to identify fracture modes. Compression and smooth tensile tests showed a linear decrease in yield strength with increasing temperature, and for tensile tests, a linear decrease in ultimate tensile strength with increasing temperature. The corresponding tensile ductility was relatively constant at temperatures above 0{degree}C, then decreased rapidly with decreasing temperature. Notched tensile tests showed a ductile-to-brittle transition at about {minus}40{degree}C. SEM photographs showed a mixture of ductile-dimple fracture and brittle cleavage areas in all notched tensile sample fracture surfaces. Fracture surfaces on smooth tensile test samples showed a ductile-dimple structure at 80{degree}C, a primarily ductile-dimple structure with some long narrow cleavage facets at 24{degree}C, and a mostly cleavage structure at {minus}54{degree}C. The mechanical threshold stress model was fit to yield stress data and the parameters for an equation describing yield stress as a function of temperature and strain rate were determined.more » 15 refs., 32 figs., 4 tabs.« less

This study examines the mechanical and microstructural characteristics of 2205 duplex stainless steel (DSS) sheets welded using Autogenous Gas Tungsten Arc Welding (A-GTAW) under optimized conditions. A 2 mm thick DSS plate was butt-welded using a welding current of 100 A, an arc length of 2.4 mm, and a welding speed of 250 mm/s. The welded joint was evaluated for tensile strength, hardness, ductility, bending performance, and formability. The joint exhibited an ultimate tensile strength of 705 MPa, representing a 34% improvement over the base metal (BM), with an elongation of 56.5%. Bending tests confirmed that the joint maintained its structural integrity under severe plastic deformation, with an r/t bending ratio of 2, demonstrating excellent ductility. Microhardness measurements showed a 12.5% increase in hardness in the fusion zone (FZ) relative to the BM, attributed to δ-ferrite and γ-austenite phase transformations. The microstructural analysis revealed the formation of Widmanstätten austenite (WiA), secondary austenite (SA), and partially transformed austenite (PTA) in the FZ, with quantified phase percentages contributing to the enhanced mechanical properties. Fractographic analysis identified ductile failure characterized by dimples, microvoid coalescence, and secondary cracks. The stress-strain curve exhibited a second jump, attributed to strain hardening effects in the welded joint. The Erichsen formability index increased by 10%, indicating superior forming behavior. These results demonstrate that A-GTAW, when applied under carefully controlled parameters, significantly enhances the mechanical performance and structural reliability of 2205 DSS joints, making it a viable technique for critical industrial applications requiring high strength, ductility, and corrosion resistance.