Microstructure and mechanical properties of high-strength low alloy steel by wire and arc additive manufacturing

A high-building multi-directional pipe joint(HBMDPJ)was fabricated by wire and arc additive manufacturing using high-strength low-alloy(HSLA)steel.The microstructure characteristics and transformation were observed and analyzed.The results show that the forming part includes four regions.The solidification zone solidifies as typical columnar crystals from a molten pool.The complete austenitizing zone forms from the solidification zone heated to a temperature greater than 1100℃,and the typical columnar crystals in this zone are difficult to observe.The partial austenitizing zone forms from the completely austenite zone heated between Ac1(austenite transition temperature)and1100℃,which is mainly equiaxed grains.After several thermal cycles,the partial austenitizing zone transforms to the tempering zone,which consistes of fully equiaxed grains.From the solidification zone to the tempering zone,the average grain size decreases from 75 to20μm.The mechanical properties of HBMDPJ satisfies the requirement for the intended application.

Determination of Surface Roughness in Wire and Arc Additive Manufacturing Based on Laser Vision Sensing

Wire and arc additive manufacturing(WAAM) shows a great promise for fabricating fully dense metal parts by means of melting materials in layers using a welding heat source. However, due to a large layer height produced in WAAM, an unsatisfactory surface roughness of parts processed by this technology has been a key issue. A methodology based on laser vision sensing is proposed to quantitatively calculate the surface roughness of parts deposited by WAAM.Calibrations for a camera and a laser plane of the optical system are presented. The reconstruction precision of the laser vision system is verified by a standard workpiece. Additionally, this determination approach is utilized to calculate the surface roughness of a multi-layer single-pass thin-walled part. The results indicate that the optical measurement approach based on the laser vision sensing is a simple and effective way to characterize the surface roughness of parts deposited by WAAM. The maximum absolute error is less than 0.15 mm. The proposed research provides the foundation for surface roughness optimization with different process parameters.

Solidification microstructure evolution and its correlations with mechanical properties and damping capacities of Mg-Al-based alloy fabricated using wire and arc additive manufacturing

Magnesium(Mg)alloys,as the lightest metal structural material with good damping capacities,have im-portant application prospects in realizing structural lightweight and vibration reduction.However,their engineering application is greatly limited by poor plastic formability.Wire and arc additive manufactur-ing(WAAM)provides a potential approach for fabricating large-scale Mg alloy components with high manufacturing flexibility.In this study,the evolution of the solidification microstructure of a WAAM-processed Mg-Al-based alloy was quantitatively analyzed based on the analytical models;then,the cor-relations between the solidification microstructure and mechanical properties/damping capacities were investigated.The results revealed that the WAAM-processed Mg-Al-based alloy with an equiaxed-grain-dominated microstructure displayed a simultaneous enhancement in mechanical properties and damping capacities compared to those of the cast Mg-Al-based alloy.The good combination of mechanical prop-erties and damping capacities are mainly attributed to the weakened basal texture with a relatively high Schmid factor for basalslip,the twinning-induced plasticity(TWIP)effect associated with the profuse{10-12}tensile twinning,and the relatively high dislocation density caused by the thermal stress during the WAAM process.

Effect of grain refinement induced by wire and arc additive manufacture (WAAM) on the corrosion behaviors of AZ31 magnesium alloy in NaCl solution

Additive manufacturing(AM)of Mg alloys has become a promising strategy for producing complex structures,but the corrosion performance of AM Mg components remains unexploited.In this study,wire and arc additive manufacturing(WAAM)was employed to produce single AZ31 layer.The results revealed that the WAAM AZ31 was characterized by significant grain refinement with non-textured crystallographic orientation,similar phase composition and stabilized corrosion performance comparing to the cast AZ31.These varied corrosion behaviors were principally ascribed to the size of grain,where cast AZ31 and WAAM AZ31 were featured by micro galvanic corrosion and intergranular corrosion,respectively.

Effect of deposition rate on microstructure and mechanical properties of wire arc additive manufacturing of Ti-6Al-4V components

Wire arc additive manufacturing(WAAM)is a novel manufacturing technique by which high strength metal components can be fabricated layer by layer using an electric arc as the heat source and metal wire as feedstock,and offers the potential to produce large dimensional structures at much higher build rate and minimum waste of raw material.In the present work,a cold metal transfer(CMT)based additive manufacturing was carried out and the effect of deposition rate on the microstructure and mechanical properties of WAAM Ti-6Al-4V components was investigated.The microstructure of WAAM components showed similar microstructural morphology in all deposition conditions.When the deposition rate increased from 1.63 to 2.23 kg/h,the ultimate tensile strength(UTS)decreased from 984.6 MPa to 899.2 MPa and the micro-hardness showed a scattered but clear decline trend.

Wire and arc additive manufacturing of dissimilar 2319 and 5B06 aluminum alloys

Aluminum alloy is the most widely used light alloy at present.By combining different types of aluminum alloys,their functional properties can be expanded.In the present research,two components composed of 2319(Al-6.5Cu)and 5B06(Al-6.4Mg)dissimilar alloys were fabricated by wire and arc additive manufacturing(WAAM).The deposited component with the bottom half of 2319 and the top half of 5B06 exhibits better mechanical properties than its counterpart deposited vice versa.Its ultimate tensile strength,yield strength,and elongation are 258.5 MPa,139.3 MPa,and 5.6%,respectively,which are only slightly inferior to the mechanical properties of 2319 base metal.The results show that for both components,fracture occurred at a layer thickness above the interface layer during the tensile test,regardless of the deposition order.It appears that the thermal stress due to the long dwell time and the remelting of the S-AlCu Mg phase are the main factors promoting crack initiation.Depending on the deposition order,cracks propagate either along the aggregated pores or stripθ-AlCu phase distributed along the grain boundary.By analyzing the heat input and selecting the appropriate depositing order,the strength of WAAM dissimilar aluminum alloys can be effectively improved through the proper control of microstructure and internal defects.

Effects of Cd addition in welding wires on microstructure and mechanical property of wire and arc additively manufactured Al-Cu alloy

Wall structures were made by cold metal transfer-based wire and arc additive manufacturing using two kinds of ER2319 welding wires with and without Cd elements. T6 heat treatment was used to improve mechanical properties of these wall structures. Due to the higher vacancy binding energy of Cd, Cd-vacancy clusters are formed in the aging process and provide a large number of nucleation locations for θ′ phases. The higher diffusion coefficient of the Cd-vacancy cluster and the lower interfacial energy of θ′ phase lead to the formation of dense θ′ phases in the heat-treated α(Al). According to the strengthening model, after adding Cd in ER2319 welding wires, the yield strength increases by 43 MPa in the building direction of the heat-treated wall structures.

Effects of cold metal transfer mode on the reaction layer of wire and arc additive-manufactured Ti-6Al-4V/Al-6.25Cu dissimilar alloys

Components of Ti and Al dissimilar alloys were obtained by wire and arc additive manufacturing using two cold metal transfer(CMT)modes.Direct current CMT(DC-CMT)mode was used for Ti alloy deposition,and DC-CMT or CMT plus pulse(CMT+P)mode was used for the Al alloy deposition.During deposition of the first Al alloy layer,little and a significant amount of Ti alloy were melted using DC-CMT and CMT+P mode,respectively.TiAl_(3)formed in the reaction layer when DC-CMT mode was used,while TiAl_(3),TiAl,and Ti3Al formed in the reaction layer when CMT+P mode was used.Compared to using DC-CMT mode,more cracks occurred when using CMT+P.The nanohardness of the reaction layer was between that of the Al and Ti alloys,irrespective of the CMT modes.The average tensile strengths of the samples using DC-CMT and CMT+P mode were 108 MPa and 24 MPa,respectively.DC-CMT mode was more suitable for the wire and arc additive manufacturing of Ti/Al dissimilar alloys.

Effects of heat treatment on microstructures and properties of a heterostructured alloy with dissimilar components fabricated by WAAM

Heat treatment significantly influences homogeneous material microstructures and mechanical properties,which can be improved by an optimal heat treatment process.However,heat treatment application to heterogeneous materials presents significant challenges due to compositional and microstructural heterogeneities.Herein,a laminated heterostructured alloy comprising alternating316L stainless steel(SS)and 18Ni300 maraging steel(MS)layers fabricated using wire and arc additive manufacturing was investigated.A solution treatment was applied at900℃for 0.5 h.Subsequently,the solution-treated and asfabricated(AF)samples were aged at 500℃for 4 h;these samples were denoted SA and AT,respectively.The AT phase compositions and orientations were similar to those of AF.The SA 316L SS layer resembled that of AF,but the SA 18Ni300 MS layers exhibited a reduced austenite phase fraction and refined grain size,attributable to solid-state transformation.In the AT sample,aging induced the formation of nanoscale acicularωphase and ellipsoidal Ni_(3)Ti,Fe_(2)Mo,and X precipitates in the 18Ni300 MS layers.Conversely,the SA precipitates contained acicular Fe Ni_(2)and ellipsoidalω,Ni_(3)Ti,and X precipitates,and their fractions were lower than those in AT precipitates.The18Ni300 MS layer microhardness in the heat-treated samples increased due to nanoprecipitation,but the 316L SS layer microhardness resembled that of AF.The AT and SA ultimate tensile strengths increased to(1360±50)and(1473±41)MPa,respectively,attributable to precipitation strengthening.The SA 316L SS layer exhibited a high stress-induced martensite fraction,enhancing the ductility of heated samples.