1,720,977 research outputs found
New approach for assessing the weldability of precipitation strengthened nickel-base superalloys
No full textElectron beam welding of difficult-to-weld austenitic stainless steel/Nb-based alloy dissimilar joints without interlayer
No full textAdditive manufacturing of functionally graded metallic materials: A review of experimental and numerical studies
No full textInspired by nature, advanced functionally graded materials (FGMs) are an appropriate response to high-performance multi-functional applications. The introduction of modern additive manufacturing technology to the processing of gradient metallic materials opened up a great opportunity for further development of this class of engineering materials owing to several advantages of this technology, e.g., high manufacturing flexibility. The phenomena prevailing in the additive manufacturing of gradient metallic materials, such as melting and solidification, have drawn special attention to this field from the viewpoint of materials science and engineering to the extent that many experimental and numerical research studies have been done in this regard in recent years. After briefly introducing FGMs and providing a brief overview of manufacturing methods with a focus on additive manufacturing processes, this paper discusses experimental studies in three sections: metal–metal, metal-ceramic, and metal-intermetallic gradient materials. Then, numerical studies are reviewed from the perspective of materials science and engineering. In the end, important results achieved so far are summarized and an outlook is provided for further research in the future
The effect of laser surface melting on the microstructure, microsegregation and solidification path of service-aged ECY768 cobalt-based gas turbine nozzle
No full textIn this study, the laser surface melting of cobalt-based superalloy ECY768, which has been in service for 40,000 h at a temperature of 1000 °C, has been investigated. Subsequently, laser surface welding and post-welding heat treatment is performed on the samples. This study was conducted in order to restore the microstructure of the damaged service-aged gas turbine nozzle to as-cast state. The results showed that by performing laser surface remelting, the microstructure of as-cast state can be approached. Also, the results of this study have investigated the weldability, microsegregation and solidification path of this superalloy, and it can be used in the repairing this superalloy in the industry. Laser surface melting was performed using a continuous wave fiber laser at various speeds of 10, 12, 14, 20, 50, and 70 mm/s. The microstructure and phase characteristics of the samples were examined using optical and scanning electron microscopes. Upon analyzing the macrostructure of the weld metal, it was observed that the depth of the melt zone at the speed of 12 mm/s is 585 ± 40 μm. In the investigating the microstructure of the solidification modes, namely planar, cellular, columnar dendritic, and equiaxed dendritic, it was observed that microsegregation occurs during laser welding of the samples due to the presence of heavy elements such as tantalum and tungsten. The solidification distribution coefficient for tantalum was calculated to be 0.37, which increased to 0.60 after the solution annealing heat treatment, resulting in an improved segregation behavior. Characterizing the surface hardness profiles of laser-melted samples it was observed that the hardness in the melt zone significantly increased compared to the base metal. The results of the current research indicate that the weldability (resistance to various welding defects, especially hot cracks) of the cobalt-based superalloy ECY768 is acceptable, and this process can be used for rejuvenating service-aged ECY768 cobalt-based gas turbine nozzle
Microstructural study of additively-manufactured carbon steel-stainless steel 316L - Inconel 625 functionally graded material: Simulation and experimental approaches
No full textThis study aims to analyze the microstructure and present phases of functionally graded carbon steel - stainless steel 316L - Inconel 625 using experimental methods and computational software (JMatPro). Both FE-SEM and SEM-EDS equipment were employed to evaluate the materials. The JMatPro software accurately simulated the present phases and their formation temperatures. The microstructure in the plain carbon steel part formed the ferrite phase at 900 °C, while a small amount of pearlite structure formed at 700 °C, remaining stable at ambient temperature. Chromium phase in stainless steel 316 L layers increased with solidification, with a higher increase in the delta ferrite phase. Inconel 625 at 1130 °C, the Laves nucleated with austenite, stable up to ambient temperature. As liquid decreased, niobium and molybdenum accumulation increased, potentially leading to Laves formation. The significant increase in niobium content at the interface of stainless steel 316L-Inconel 625 is attributed to an increase in iron content. The research indicated a good correlation between the observed and predicted microstructures
Effect of electron beam welding current variations on the microstructure and mechanical properties of Nb-1Zr advanced alloy
No full textMetallurgical, physical, mechanical and oxidation behavior of lead-free chromium dissolved Sn–Cu–Bi solders
No full textAccording to the European Union's (EU) legislation in 2006, the Restriction of Hazardous Substances (RoHS) led to eliminating Sn–Pb conventional solders from electronic assemblies. Despite this elimination, the use of lead-bearing solders in car electronics was persisted, and eventually, in 2014 the lead usage prohibition was introduced for the automotive industry. The reliability and safety issues are still arguable in this industry, notwithstanding the lead-free solders substitution. The Sn–Cu solder is one of the alternatives modified by alloying elements to improve its moderate mechanical properties. In order to fabricate a cost-effective solder that has simultaneously a good level of mechanical properties and oxidation behavior, the Cr along with Bi was added to the Sn–Cu base solder. In this research, a comparative study has been conducted on the Sn-0.8Cu-1.8Bi-xCr (x = 0, 0.01, 0.1 wt.%). The effect of adding these alloying elements on the physical and mechanical properties is studied compared to Sn-0.8Cu and Sn-0.8Cu-1.8Bi solders. The physical properties of synthesized solders such as microstructure, XRD, thermal properties, wettability, oxidation behavior, and density were investigated. Also, these experienced mechanical tests such as uniaxial tensile test, microhardness test, and fractography to evaluate the effect of Cr and Bi on mechanical properties. The results showed that the addition of the minor amount of Cr along with Bi can consequently improve the microstructure, add some kinds of new IMCs, modifies the oxidation behavior and the wettability. The mechanical properties of the base solder got better by the adding these alloying elements
The effect of Nd:YAG laser pulse duration and post-weld heat treatment on the microstructure and mechanical properties of laser-welded NiTi shape memory alloy
No full textThe heat input is the most critical factor in pulsed Nd:YAG laser welding and affects the microstructure and mechanical behavior of the welded alloys. NiTi alloy has been used for various applications such as medical equipment and MEMS due to its unique shape memory effect, superelasticity, and excellent corrosion and fatigue performance. This research investigated the effect of heat input and post-weld heat treatment (PWHT) on the microstructure and mechanical properties of similar NiTi shape memory wires joints. For this purpose, NiTi wires were welded with pulse widths of 5, 8, and 11 ms, and then, heat treatment was performed. Microstructures of the welded alloys were examined using optical and electron microscopes and chemical composition was analyzed with an EDS analysis system. The mechanical properties were evaluated using tensile and microhardness tests. A desirable NiTi SMA joint was achieved by Nd:YAG laser, and the properties were improved by following post weld heat treatment.Investigations showed that microstructure and mechanical properties were changed by increasing the heat input. After applying PWHT due to recrystallization and the creation of new phases in the weld zone, the final strength of the joints increased up to 80%, and the behavior of the plateau region became similar to shape memory behavior in the NiTi alloy
Investigating the microstructure and mechanical properties in furnace brazing Ti–6Al–4V to 17-4 PH stainless steel dissimilar joint with BNi-2 filler metal
No full textDue to the distinct physical and metallurgical characteristics of titanium and steel, the welding of these two materials poses challenges and holds significant importance. This study investigates the impact of brazing time and temperature on the microstructure and mechanical properties of dissimilar brazing between 17-4 PH stainless steel and Ti–6Al–4V using BNi-2 as a filler metal, focusing on the formation of brittle compounds like FeTi and Fe2Ti during the brazing process. The joint between these materials is commonly utilized in various industrial applications. The assessment involved the use of optical microscope, scanning electron microscope, shear – tensile test, microhardness test, and wettability measurement. Brazing of the base metals was conducted at temperatures of 1050/1100 °C for durations of 15 and 30 min to determine the optimal temperature and time combination. The results indicated that the best joint properties were achieved at 110 °C for 15 min, with an average shear strength of 38.46 MPa. Contact angle measurements revealed that BNi-2 exhibited superior wettability on 17-4 PH compared to Ti–6Al–4V. Furthermore, increasing the temperature from 1050 to 1100 °C led to a reduction in contact angle from 9.98 to 8.83° for 17-4 PH, and from 16.51 to 10.12° for Ti–6Al–4V indicating an improvement in wettability
- …
