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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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Microstructure refinement and properties of 1.0C-1.5Cr steel in a duplex treatment combining double quenching and laser surface quenching
摘要： The 1.0C-1.5Cr steel was subjected to conventional quenching and laser surface quenching treatment. A process combing double quenching and laser surface quenching was proposed for enhancing surface hardness and obtaining finer microstructure. The cementite dissolution and grain growth behavior in the austenitizing process of single quenching, double quenching, and laser surface quenching were studied. The results indicated that compared with single quenching, mean diameter of undissolved cementite particles (UCP) was much finer in double quenching, and the final prior austenite grain size (PAGS) could be decreased by nearly 40% to about 4.5 μm. Both grain and cementite particles near the surface will coarsen after laser surface treatment. Compared with single quenching, the PAGS within hardened layer can be decreased by at least 11% through double quenching, and the mean diameter of UCP at the bottom of hardened layer can be decreased by about 20%. Compared with conventional quenching, surface hardness was enhanced by about 20% through laser surface quenching, contributing to the wear resistance. However, the hard and brittle surface layer tends to be crack source during the impact process, leading to the deterioration of final impact toughness. Under the identical laser parameters, the impact absorbed energy is similar in both single and double quenching, which is about 25% of that before laser surface quenching. The impact absorbed energy can be increased from 22J to 28J by preheating at 160 C during the laser surface quenching.
关键词： Impact toughness,Grain size,Cementite,Laser surface quenching,Double quenching,Wear
更新于2025-09-19 17:13:59
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Effects of Stress-Relieving Heat Treatment on Impact Toughness of Direct Metal Laser Sintering (DMLS)-Produced Ti6Al4V (ELI) Parts
摘要： The impact toughness of as-built (AB) and stressed-relieved (SR) direct metal laser sintering-produced Ti6Al4V (ELI) was investigated using the standard Charpy impact test over the temperature range of ?130°C to 250°C. Stress-relieving heat treatment was conducted at 650°C for a soaking period of 3 h in argon gas atmosphere. The results showed improvements in the impact toughness after stress-relieving heat treatment. Stress relieving also shifted the established ductile-to-brittle transition temperature to lower temperatures. Comparative analysis of the impact toughness values for AB and SR specimens at ambient temperature showed them to be 48% and 22% lower than recommended values for use in aircraft structures, respectively.
关键词： Impact Toughness,Stress-Relieving Heat Treatment,Ti6Al4V (ELI),Direct Metal Laser Sintering,Charpy Impact Test
更新于2025-09-12 10:27:22