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Filler metal distribution and processing stability in laser-arc hybrid welding of thick HSLA steel
摘要： Welds made by high power laser beam have deep and narrow geometry. Addition of filler wire by the arc source, forming the laser-arc hybrid welding (LAHW) process, is very important to obtain required mechanical properties. Distribution of molten wire throughout the entire weld depth is of concern since it tends to have low transportation ability to the root. Accurate identification of filler metal distribution is very challenging. Metal-cored wires can provide high density of non-metallic inclusions (NMIs) which are important for acicular ferrite nucleation. Accurate filler distribution can be recognized based on statistical characterization of NMIs in the weld. In the present study, it was found that the amount of filler metal decreased linearly towards the root. The filler metal tends to accumulate in the upper part of the weld and has a steep decrease at 45–55 % depth which also has wavy pattern based on longitudinal cuts. Substantial hardness variation in longitudinal direction was observed, where in the root values can reach > 300 HV. Excessive porosity was generated at 75 % depth due to unstable and turbulent melt flow based on morphology of prior austenite grains. The delicate balance of process parameters is important factor for both process stability and filler metal distribution.
关键词： Filler metal distribution,Microstructure,Thick steel,Non-metallic inclusions,High strength steel,Mechanical properties,Laser-arc hybrid welding
更新于2025-09-23 15:19:57
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Study on mechanical and metallurgical properties of fiber laser welded Nb-1% Zr-0.1% C alloy
摘要： Laser welding of Nb-1% Zr-0.1% C was attempted in butt-welding configuration using top and bottom sided inert gas shielding. The precautionary measure during welding was to limit the reactivity of niobium alloy in ambient atmosphere. The ranges of input parameters, that is, laser power (P), welding speed (V) and beam diameter (D) for full penetration welding were attempted by carrying out bead-on-plate (BOP) experiments. The selection of the combination of process parameters was such that the formed weld area could be minimized without hampering the depth of penetration. Bead-geometry, hardness and tensile strength were quantified to study the influence of input process parameters during laser welding. Base metal had an average hardness of 108 VHN and the average hardness of fusion zone (FZ) was found to lie between 278 and 546 VHN. The steeper increment in microhardness value of the FZ could be due to the grain refinement, dissolution of precipitates and formation of brittle intermetallic phases of carbide and oxides, which were evident by the result of energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) phase analysis. The weld joint that failed in the weld zone exhibited the brittle failure, and ductile mode was achieved in the joint, where failure occurs at base metal. The range of elongation in laser welded joints varied in between 1.97 and 5.73 mm. The reduction of tensile strength and ductility of the joints could be due to marginal enhancement of microhardness and increment of brittle phase density in fusion zone, as were evident from XRD phase analysis. The main focus of the present work was intended towards the establishment of laser welding as an alternative technique for fabrication of reactive niobium alloy in ambient atmosphere.
关键词： Cooling rate,Laser welding,Grain refinement,Niobium alloy,Mechanical properties,Nb-1% Zr-0.1% C
更新于2025-09-23 15:19:57
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Rationally designed functionally graded porous Ti6Al4V scaffolds with high strength and toughness built via selective laser melting for load-bearing orthopedic applications
摘要： Functionally graded materials (FGMs) with porosity variation strategy mimicking natural bone are potential high-performance biomaterials for orthopedic implants. The architecture of FGM scaffold is critical to gain the favorable combination of mechanical and biological properties for osseointegration. In this study, four types of FGM scaffolds with different structures were prepared by selective laser melting (SLM) with Ti6Al4V as building material. All the scaffolds were hollow cylinders with different three-dimensional architectures and had gradient porosity resembling the graded-porous structure of human bone. Two unit cells (diamond and honeycomb-like unit cells) were used to construct the cellular structures. Solid support structures were embedded into the cellular structures to improve their mechanical performances. The physical characteristics, mechanical properties, and deformation behaviors of the scaffolds were compared systematically. All the as-built samples with porosities of ~52–67% exhibited a radial decreasing porosity from the inner layer to the outer layer, and their pore sizes ranged from ~420 to ~630 μm. The compression tests showed the Young’s moduli of all the as-fabricated samples (~3.79–~10.99 GPa) were similar to that of cortical bone. The FGM structures built by honeycomb-like unit cells with supporting structure in outer layer exhibited highest yield strength, toughness and stable mechanical properties which is more appropriate to build orthopedic scaffolds for load-bearing application.
关键词： Additive manufacturing,Orthopedic scaffolds,Mechanical properties,Functionally graded materials
更新于2025-09-23 15:19:57
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Selective Laser Melting and Remelting of Pure Tungsten
摘要： The processing of pure tungsten encounters a substantial challenge due to its high melting point and intrinsic brittleness. Selective laser melting (SLM) technique is gaining popularity and offers an excellent processing approach for refractory metals. Herein, dense pure tungsten specimens are produced by optimizing SLM processing parameters. The mechanical property of the SLM-produced tungsten with an ultimate compressive strength of about 1200 MPa, which is obviously superior to that reported in other literature, is achieved. The increased laser energy input is instrumental in raising density and surface roughness of tungsten specimens. Interestingly, additional remelting of processed layers during SLM improves the surface quality and the microstructure and achieves the highest relative density (98.4% (cid:1) 0.5%). After laser remelting, the surface roughness is reduced by 28% and a large number of ?ne grains are obtained. The ?ow of ?uids caused by remelting plays a decisive role in the formation of ?ne grains and the defect level. Therefore, these ?ndings offer a new insight into SLM of pure tungsten.
关键词： microstructure,tungsten,selective laser melting,mechanical properties,laser remelting
更新于2025-09-23 15:19:57
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Effect of fiber laser welding on solute segregation and proprieties of CoCrCuFeNi high entropy alloy
摘要： The effect of fiber laser welding on solute segregation and proprieties of CoCrCuFeNi high entropy alloy was investigated. The microstructure and mechanical properties of the parent metal and the fusion zone were comparably studied. The parent metal was dendrite, with elemental Cu segregated to interdendrites owing to small bonding energies with Fe, Co, Ni, and Cr atoms. After laser welding, the microstructure in the center of the fusion zone was predominantly equiaxial grains, whereas that in the edge region was mainly columnar crystals oriented perpendicular to the fusion line. The segregation of Cu in the fusion zone is alleviated by grain refinement and molten pool agitation. Because of the fine-grain strengthening and precipitation hardening effect, the hardness and yield stress of the fusion zone are 12.84% and 26.87% greater than those of the parent metal, respectively.
关键词： CoCrCuFeNi,mechanical properties,fiber laser welding,solute segregation
更新于2025-09-23 15:19:57
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Experimental Study of the Technology Parameters Affect in the Laser Welded Joints
摘要： The laser welding technology is improving immediately rapidly nowadays. It has many advantages again the traditional welding technologies. The heat affected zone in case of the laser welding is very thin and the penetration of the joint is depth. This high energy technology work by a focused high energy laser light accompanied by protective gases. For welding process well known the different laser devices (gas laser, solid-state laser, disc laser). The effect of the gases and the technological parameters are not well known yet. In this work, we wanted to find some relationship between the welding parameters and the joint mechanical properties. To find this relationship it was welded the joint by different technologies parameters and the samples experimented the joint mechanical properties with different parameters and controlled by the experimental way.
关键词： technology parameters,Nd:YAG laser,laser welding,joint mechanical properties,CO2 laser
更新于2025-09-23 15:19:57
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Recent progress in laser additive manufacturing of aluminum matrix composites
摘要： Laser additive manufacturing (LAM) can produce high-performance and near net shape parts of aluminum matrix composite (AMC) with higher specific strength, better wear resistance and more outstanding physical properties than aluminum alloys, which are widely used in automotive and aerospace fields. This article covers emerging researches on particle-reinforced AMCs fabricated by LAM techniques. The current research status is reviewed from the perspectives of powder preparation, microstructure characterization and mechanical properties. The microstructure evolution of AMCs is discussed in depth and the formation mechanism of in situ phase is analyzed. In addition, different strengthening mechanisms of AMCs are studied in detail. The last part summarizes the merits and demerits of AMCs and proposes the existing problems and future research directions.
关键词： Laser additive manufacturing,Mechanical properties,Microstructure,Aluminum matrix composites,Strengthening mechanisms
更新于2025-09-23 15:19:57
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ANALYSIS OF THE PROPERTIES OF AW2099 ALUMINIUM-LITHIUM ALLOY WELDED BY LASER BEAM WITH AW5087 ALUMINIUM-MAGNESIUM FILLER MATERIAL
摘要： EN AW2099 aluminium lithium alloy, 2.0 mm in thickness, was used as an experimental material. EN AW2099 belongs to the 3rd generation of aluminium lithium alloys. The third generation was developed to improve the disadvantages of the previous generation, such as anisotropy in mechanical properties, low fracture toughness, corrosion resistance and resistance to fatigue crack growth, as well. Aluminium magnesium 5087 ?ller wire with a diameter of 1.2 mm was used for the welding. Crack free weld joints were produced after an optimization of welding parameters. The microstructure of weld metal and mechanical properties of weld joints were investigated. Equiaxed zone (EQZ) was observed at the fusion boundary. The character of grains changed in the direction towards the weld centre, from the columnar dendrite zone to equiaxed dendrite zone in the weld centre. The microstructure of the weld metal matrix consisted of α-aluminium. Alloying elements enrichment was found at the inter-dendritic areas, namely copper and magnesium. The microhardness decrease in the weld metal due to a dissolution of strengthening precipitates was measured. The microhardness was slightly higher in comparison to a weld produced by a laser welding without a ?ller material. The tensile strength of the weld joint reached around 67 % of the base material’s strength and the fracture occurred in the weld metal.
关键词： electron microscopy,microstructure,Aluminium lithium alloy,laser beam welding,equiaxed zone,mechanical properties
更新于2025-09-23 15:19:57
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A fundamental investigation on threea??dimensional laser material deposition of AISI316L stainless steel
摘要： Laser material deposition (LMD), a direct laser deposition additive manufacturing technology, has been widely used to build full density metal parts. However, owing to the parallel deposition way which is universal used in LMD process, the staircase e?ect is presented even the collision occurs during the shape of target part is irregular and relatively complex. In this paper, the appropriate range of z-increment, which can assure the thin-walled part is perfectly fabricated, was veri?ed initially. Based on the e?ects of defocusing and z-increment on the deposited height, a novel three-dimensional laser material deposition process, which can provide new ways of avoiding the staircase e?ect and eluding the collision, was proposed. An experimental investigation, which contains the e?ects of deposition strategies (parallel and three-dimensional deposition way) and slope angle on the microstructures, hardness, and tensile properties of the fabricated slope thin-walled part, was conducted. The results showed that the grain size near the high side of slope thin-walled part increased with the increase of the slope angle regardless of the deposition way due to the increased accumulated heat. The average hardness of the parts with di?erent deposition way were basically the same, but the distributions of harness were quite di?erent. In addition, with the increase of the deposition height, the hardness increased until the distance to the substrate was about 25 mm and then decreased. The UTS and elongation of the LMD part in parallel deposition way were slightly higher than those of the part in three-dimensional deposition way. The UTS and elongation increased ?rstly and then decreased with the increase of the angle (β) between tensile loading direction and horizontal direction regardless of the deposition way. In the case of parallel and three-dimensional deposition way, the biggest UTS was presented during the β was 45° and 25° respectively because the direction of tensile loading was approximately perpendicular to the sliding surface that ensure the shearing force was smallest and the boundaries of molten pool could su?er from the highest tensile force. The smallest UTS showed when the β was 90°.
关键词： Mechanical properties,Z-increment,Microstructures,Three-dimensional deposition way,Laser material deposition
更新于2025-09-23 15:19:57
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Study of Microstructure and Properties of 316L with Selective Laser Melting Based on Multivariate Interaction Influence
摘要： The selective laser melting technique is widely used in aerospace and biomedical industries, and the performance of formed 316L parts is significantly subject to the forming angle. As the selective laser melting 316L parts are constrained by multiple performance indexes, the study involves multivariate interaction influenced on the forming parameters such as the angle with the xz plane, the angle with the xy plane, laser power, scan speed, powder thickness, and hatching space on the indexes like tensile strength, density, and surface roughness with linear regression equations based on multiobjective optimization to obtain the best process parameters. The study results of microstructure performance of the formed 316L parts show that the angle with the xz plane has significant effect on the experiment indexes, while the layer thickness has the greatest effect on the indexes. After stretching, the molten pools are obviously elongated and the microstructure of the formed 316L parts is composed of equiaxed crystals and columnar crystals with a grain width of 0.28–0.4 nm. The secondary growth of the dendrites is not obvious, and the crystallinity of the selective laser melting 316L parts is not as good as the standard parts, with the microstructure showing directional solidification due to grain refinement and microscopic distortion of crystals. As the fracture has dimples, it is a ductile fracture and typical plastic fracture. The hardness near the fracture is higher than that of the substrate, whilst the indexes regarding the selective laser melting parts are higher than the ASTM-A182 and ASTM-F3184-16 standards. Since the theoretical model built in this study has less error, the findings have practical engineering application value.
关键词： microstructure,multivariate interaction,selective laser melting,mechanical properties,316L stainless steel
更新于2025-09-23 15:19:57