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Influence of processing parameters on the microstructure and tensile property of 85 W-15Ni produced by laser direct deposition
摘要： The plate-like shape 85W-15Ni parts were produced by laser direct deposition technology with different processing parameters (laser power and scanning speed). The influence of processing parameters and their corresponding laser energy density on the microstructural characterization, phase composition and tensile property of 85W-15Ni samples was investigated. The results show that the relative density of samples increased with the laser energy density and the densification trend started to slow as the laser energy density reached 380-400 J/mm3, though the highest density value was obtained with laser energy of 425 J/mm3. With the increase of laser energy density, more disorder and fine W dendrites existed at the bonding region between deposition layers and more W-W grain boundaries formed at the central region of the layer. The 85W-15Ni samples produced with different processing parameters consisted of W and γ-Ni phase. To improve the tensile property, it is necessary to increase the laser energy density to obtain denser structure and reduce the residual pores or gaps. However, the excessive laser energy density resulted in the formation of more W-W grain boundaries that were detrimental to the tensile property. The best tensile properties were obtained at the laser energy density of 395 J/mm3.
关键词： 85W-15Ni,Laser direct deposition,Tensile property,Laser energy density,microstructural characterization
更新于2025-11-28 14:24:20
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Effects of laser shock peening on microstructure and fatigue behavior of Tia??6Ala??4V alloy fabricated via electron beam melting
摘要： Laser shock peening (LSP) is a post-treatment process that is widely used to modify the surface microstructure and mechanical properties of parts constructed by additive manufacturing (AM). In this study, the influence of LSP on the microstructure and fatigue behavior of Ti–6Al–4V alloy manufactured via electron beam melting (EBM), a popular method of AM, was investigated. The microstructure of the EBM sample consisted of the β phase (~6 vol%) and α lamellar phase. Grain refinement of the α phase occurred via both dislocation evolution and deformation twinning during LSP. A theoretical description of the microstructural evolution, particularly the distribution of deformation twins, was developed. The fatigue strength and micro-hardness of the EBM samples increased by approximately 17% and 11% after LSP treatment, respectively. The fatigue fracture morphologies at three defined damage stages (crack initiation, crack propagation, and instantaneous rupture) were examined for EBM samples before and after LSP. The dominant mechanism of fatigue strength enhancement by LSP was discussed. The effects of residual compressive stress assistant with adiabatic temperature increase and grain refinement of the α phase produced by LSP reduced the pre-existing crack size, suppressed crack initiation, and increased the required work for fatigue fracture.
关键词： Laser shock peening,Electron beam melting,Ti–6Al–4V titanium alloy,Fatigue behavior,Microstructural characterization
更新于2025-09-23 15:19:57
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An insight into microstructural heterogeneities formation between weld subregions of laser welded copper to stainless steel joints
摘要： The effect of laser beam welding (LBW) process on the microstructure?mechanical property relationship of a dissimilar weld between the copper (Cu) and stainless steel (SS) was investigated. Backscattered electron (BSE) based scanning electron microscopy (SEM) imaging was used to characterize the highly heterogeneous microstructural features across the LBW (Cu?SS) weld. The BSE analysis thoroughly evidenced the complex microstructures produced at dissimilar weld interfaces and fusion zone along with the compositional information. Widely different grain growths from coarse columnar grains to equiaxed ultrafine grains were also evident along the Cu?weld interface. A high-resolution electron backscattered diffraction (EBSD) analysis confirmed the existence of the grain refinement mechanism at the Cu?weld interface. Both tensile and impact properties of the dissimilar weld were found to be closely aligned with the property of Cu base metal. Microhardness gradients were spatially evident in the non-homogeneous material composition zones such as fusion zone and the Cu?weld interface regions. The heterogeneous nucleation spots across the weld sub-regions were clearly identified and interlinked with their microhardness measurements for a holistic understanding of structure?property relationships of the local weld sub-regions. The findings were effectively correlated to achieve an insight into the local microstructural gradients across the weld.
关键词： impact toughness,laser beam welding,stainless steel,microstructural characterization,copper,tensile property
更新于2025-09-23 15:19:57
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Experimental Optimization of Nimonic 263 Laser Cutting Using a Particle Swarm Approach
摘要： This paper presents an experimental study carried out on Nimonic 263 alloy sheets to determine the optimal combination of laser cutting control factors (assisted gas pressure, beam focus position, laser power, and cutting speed), with respect to multiple characteristics of the cut area. With the aim of designing laser cutting parameters that satisfy the specific specifications of multiple responses, an advanced multiresponse optimization methodology was used. After the processing of experimental data to develop the process measure using statistical methods, the functional relationship between cutting parameters and the process measure was determined by artificial neural networks (ANNs). Using the trained ANN model, particle swarm optimization (PSO) was employed to find the optimal values of laser cutting parameters. Since the effectiveness of PSO could be affected by its parameter tuning, the settings of PSO algorithm-specific parameters were analyzed in detail. The optimal laser cutting parameters proposed by PSO were implemented in the validation run, showing the superior cut characteristics produced by the optimized parameters and proving the efficacy of the suggested approach in practice. In particular, it is demonstrated that the quality of the Nimonic 263 cut area and the microstructure were significantly improved, as well as the mechanical characteristics.
关键词： artificial neural networks (ANNs),microhardness,laser cutting,microstructural characterization,Nimonic 263,parameters optimization,particle swarm optimization,simulated annealing (SA),surface roughness
更新于2025-09-16 10:30:52
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High-Brightness and High-Power Laser Welding of Powder Metallurgy Shape Memory Alloy: Welding-Parameter-Dependent Microstructure
摘要： Despite the growing interest in using powder metallurgy shape memory alloys, there is limited research on their joining and welding aiming to expand their applications. In this research, we utilized a high-power, high-brightness disk laser welding process to join spark-plasma-sintered Ti-51 at.% Ni shape memory alloy and studied the primary factors that affect the strength and functionality of the created sound welds such as intermetallics and martensite (B19￠) phase formation. The introduction of high-power laser could impede the formation of B19￠ and undesirable intermetallics such as TiNi3 and Ti2Ni; however, the desired Ti3Ni4 would also be suppressed and post-weld heat treatment was necessary to induce them again. The microstructure of fusion zones was significantly altered, producing coarse columnar grains with centerline and equiaxed weld centers. Additionally, high-power laser welding of powder metallurgy Ti-Ni alloy triggered amorphous phase formation in the welds due to rapid cooling. It was found that a laser power of 3 kW and welding speed of 6 m/min are optimal welding parameters, since the produced weld solidified along favorable [001] direction of strain recovery in Ti-Ni shape memory alloys.
关键词： disk laser welding,microstructural characterization,shape memory alloys,spark plasma sintering
更新于2025-09-16 10:30:52
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Fiber laser-MAG hybrid welding of DP/AISI 316 and TWIP/AISI 316 dissimilar weld
摘要： In this paper, TWinning-Induced Plasticity (TWIP), Dual Phase (DP) and austenitic stainless (AISI 316) steels were joined together by hybrid laser/arc welding with an austenitic steel filler. Microstructural and mechanical characterization of welded joints was carried out by optical microscopy, microhardness, tensile and bend tests. The heat affected zone (HAZ) at the TWIP side was fully austenitic and exhibited a grain coarsening; at the DP side, new martensite formed close to the fusion zone and other phase transformations occurred moving toward the base metal; at the AISI 316 side, stringers of untreated ferrite δ inside the austenitic matrix was observed. All the tensile welded specimens broke within austenitic stainless steel. TWIP/AISI 316 welds exhibited a greater tensile strength than DP/AISI 316 ones. The bending tests confirmed the ductility of both sorts of joints.
关键词： Dissimilar weld,AISI 316 steel,Hybrid laser arc welding,Mechanical and microstructural characterization,Austenitic filler,Twip steel,DP steel
更新于2025-09-12 10:27:22