Arc additive manufacturing of gradient hot forging die with shaped waterways

Under the working environment of high temperature and strong load impact,hot forging die is prone to failure which reduces the service life of die.Using arc additive manufacturing in the die cavity,a gradient material hot forging die with high precision,superior per-formance,and conformal cooling channels is developed.This improves the toughness of the die cavity and reduces the working temperature,thereby forming an isothermal field,which is an effective method to enhance the lifespan of the hot forging die.Three kinds of gradient flux-cored wires are designed for the surface of 5CrNiMo steel,and the microstructure and mechanical properties between gradient interfaces were studied.Based on the spatial curved structure of shaped waterways in the hot forging die cavity,a study was conducted on the strategy of partitioned forming for the manufacturing of the die with shaped waterways.In order to avoid interference with the arc gun,the hot for-ging die is divided into four regions,namely the transition region,upper,middle,and lower region,based on a combination of cavity depth and internal U-shaped and quadrilateral structures.The results show that the developed flux-cored wires have good moldability with straight sides of deposited metal under different process parameters and flat surface without cracks,pores and other defects.Under the same working conditions,the life of hot forging die formed by the gradient materials is more than multiple times that of the single material hot forging die,and the temperature gradient field of the shaped waterway die is 7℃/cm smaller than that of traditional straight waterway.

Customized heat treatment process enabled excellent mechanical properties in wire arc additively manufactured Mg-RE-Zn-Zr alloys

Customized heat treatment is essential for enhancing the mechanical properties of additively manufactured metallic materials,especially for alloys with complex phase constituents and heterogenous microstructure.However,the interrelated evolutions of different microstructure features make it difficult to establish optimal heat treatment processes.Herein,we proposed a method for customized heat treatment process exploration and establishment to overcome this challenge for such kind of alloys,and a wire arc additively manufactured(WAAM)Mg-Gd-Y-Zn-Zr alloy with layered heterostructure was used for feasibility verification.Through this method,the optimal microstructures(fine grain,controllable amount of long period stacking ordered(LPSO)structure and nano-scaleβ'precipitates)and the corresponding customized heat treatment processes(520°C/30 min+200°C/48 h)were obtained to achieve a good combination of a high strength of 364 MPa and a considerable elongation of 6.2%,which surpassed those of other state-of-the-art WAAM-processed Mg alloys.Furthermore,we evidenced that the favorable effect of the undeformed LPSO structures on the mechanical properties was emphasized only when the nano-scaleβ'precipitates were present.It is believed that the findings promote the application of magnesium alloy workpieces and help to establish customized heat treatment processes for additively manufactured materials.

Study on anisotropy of microstructure and mechanical properties of AZ31 magnesium alloy fabricated by wire arc additive manufacturing

Based on wire arc additive manufacturing(WAAM)technology,AZ31 magnesium alloy in bulk was successfully fabricated,and its microstructure as well as mechanical properties in different planes were observed and analyzed.The AZ31 magnesium alloy has a similar microstructure in the building direction(Z)and travel direction(X),both of which are equiaxed grains.There are heat-affected zones(HAZs)with coarse grains below the fusion line.The second phase is primarily composed of the Mg17Al12 phase,which is evenly distributed in different directions.In addition,the residual stress varies in different directions.There is no significant difference in the hardness of the AZ31 alloy along the Z and X directions,with the average hardness being 68.4 HV and 67.9 HV,respectively.Even though the specimens’ultimate tensile strength along the travel direction is higher in comparison to that along the building direction,their differences in elongation and yield strength are smaller,indicating that the anisotropy of the mechanical properties of the material is small.

Deformation Characteristics and Mechanical Properties of Ti/Al Bimetallic Composite Materials Fabricated by Wire Plus Arc Additive Manufacturing

We focused on Ti/Al composite materials fabricated by wire and arc addictive manufacturing,and the microstructure and interface characteristics of them before and after hot compression deformation were compared.After compression deformation,allαstructures of titanium were compacted with the emergence of Widmanstatten structures.Coarsened coloniesαof titanium were elongated and waved along the original growth direction,resulting in anisotropy of grains.Pores and Ti/Al intermetallic compounds of aluminum are significantly decreased after hot compression.Meanwhile,a good bonding interface between titanium and aluminum is obtained after hot compression,and the element diffusion is more intense.In addition,the mechanical properties and fracture behaviors of Ti/Al composite material with different clad ratio that is defined as the ratio of the thickness of titanium to that of the Ti/Al composite material are investigated by uniaxial tensile test.The experimental results show that the ultimate tensile strength of Ti/Al composite material is between that of single deposited titanium and aluminum,while the elongation of Ti/Al composite material with low clad ratio is lower than that of single aluminum due to the metallurgical reaction.As the clad ratio increases,the two component layers are harder to separate during deformation,which is resulted from the decrease of the inward contraction stress of three-dimensional stress caused by necking of aluminum.This work may promote the engineering application of Ti/Al bimetallic structures.

Wire arc additive manufacturing of a heat-resistant Al-Cu-Ag-Sc alloy:microstructures and high-temperature mechanical properties

With a high energy efficiency,low geometric limitation,and low cracking susceptivity to cracks,wire arc additive manufacturing(WAAM)has become an ideal substitute for casting in the manufacturing of load-bearing high strength aluminum components in aerospace industry.Recently,in scientific researches,the room temperature mechanical performance of additive manufactured high strength aluminum alloys has been continuously broken through,and proves these alloys can achieve comparable or even higher properties than the forged counterpart.Since the aluminum components for aerospace usage experience high-low temperature cycling due to the absence of atmosphere protection,the high temperature performances of additive manufactured high strength aluminum alloys are also important.However,few research focuses on that.A special 2319Ag Sc with 0.4 wt.%Ag and 0.2 wt.%Sc addition designed for high temperature application is deposited successfully via cold metal transfer(CMT)based on WAAM.The microstructures and high temperature tensile properties are investigated.The results show that the as-deposited 2319Ag Sc alloy presents an alternate distribution of columnar grains and equiaxed grains with no significant textures.Main second phases are Al_(2)Cu and Al3Sc,while co-growth of Al_(2)Cu and bulk Al_(3)Sc is found on the grain boundary.During manufacturing,nanoscale Al_(2)Cu can precipitate out from the matrix.Ag and Mg form nano-scaleΩphase on the Al_(2)Cu precipitates.At 260℃,average yield strengths in the horizontal direction and vertical direction are 87 MPa±2 MPa,87 MPa±4 MPa,while average ultimate tensile strengths are 140 MPa±7 MPa,141 MPa±11 MPa,and average elongations are 11.0%±2.5%,13.5%±3.0%.Anisotropy in different directions is weak.

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.

Enhanced strength-ductility synergy in a wire and arc additively manufactured Mg alloy via tuning interlayer dwell time

Strength-ductility trade-off is a common issue in Mg alloys. This work proposed that a synergistic enhancement of strength and ductility could be achieved through tuning interlayer dwell time(IDT) in the wire and arc additive manufacturing(WAAM) process of Mg alloy.The thermal couples were used to monitor the thermal history during the WAAM process. Additionally, the effect of different IDTs on the microstructure characteristics and resultant mechanical properties of WAAM-processed Mg alloy thin-wall were investigated. The results showed that the stable temperature of the thin-wall component could reach 290 ℃ at IDT=0s, indicating that the thermal accumulation effect was remarkable. Consequently, unimodal coarse grains with an average size of 39.6 μm were generated, and the resultant room-temperature tensile property was poor. With the IDT extended to 60s, the thermal input and thermal dissipation reached a balance, and the stable temperature was only 170 ℃, closing to the initial temperature of the substrate. A refined grain structure with bimodal size distribution was obtained. The remelting zone had fine grains with the size of 15.2 μm, while the arc zone owned coarse grains with the size of 24.5 μm.The alternatively distributed coarse and fine grains lead to the elimination of strength-ductility trade-off. The ultimate tensile strength and elongation of the samples at IDT=60s are increased by 20.6 and 75.0% of those samples at IDT=0s, respectively. The findings will facilitate the development of additive manufacturing processes for advanced Mg alloys.

Microstructure and mechanical properties of TA15/TC11 graded structural material by wire arc additive manufacturing process

A graded structural material(GSM)with a material transition from TA15 to TC11 was fabricated by wire arc additive manufacturing(WAAM)method.The grain morphology,chemical composition,microstructure and mechanical properties of the as-deposited GSM were all characterized to investigate their variations along the deposition direction.The results indicate that from TA15 to TC11,the grain size decreases and a transition from columnar grains to equiaxed grains occurs.The content of alloy element alters greatly within a short distance,and the width of the mutation zone is 800μm.Both TA15 and TC11 regions exhibit basketweave microstructure withα-phase andβ-phase.However,during the transition from TA15 to TC11,theα-lath becomes fine,which leads to an increase in microhardness.The tensile test shows that the bonding strength at the interface is higher than the longitudinal strength of TA15,and the lateral elongation at the interface is higher than that of TA15 and TC11.

Effect of heat treatment on the microstructure and mechanical properties of AZ80M magnesium alloy fabricated by wire arc additive manufacturing

To maximize the benefits of wire arc additive manufacturing(WAAM)processes,the effect of post-deposition heat treatment on the microstructure and mechanical properties of WAAM AZ80M magnesium(Mg)alloy was investigated.Three different heat treatment procedures(T4,T5 and T6)were performed.According to the results,after T4 heat treatment,the microsegregation of alloying elements was improved with the eutectic structure dissolved.Samples after T5 heat treatment inherited the net-like distribution of secondary phases similar to the as-deposited sample,where the eutectic structure covering the interdendritic regions and theβ-phase precipitated around the eutectic structure.After T6 heat treatment,the tinyβ-phases re-precipitated from the matrix and distributed in inner and outer of the grains.The hardness distribution of the samples went through T4 and T6 heat treatment was more uniform in comparison to that of T5 heat treated samples.The tensile test showed that the T6 heat treatment improved the strength and ductility,and the anisotropy between horizontal and vertical can be eliminated.Moreover,T4 treated samples exhibited highest ductility.

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.

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 4043 Al alloy using a cold metal transfer method

Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts were also characterized.Experimental results showed that welding at a speed of 8 mm/s and a wire feeding speed of 4.0 m/min was suitable to manufacture thin-walled parts,and the reciprocating scanning method could be adopted to manufacture thick-walled parts.The thin-walled parts of the C+P mode had fewer pores than those of the cold metal transfer(CMT)mode.The thin-and thick-walled parts of the C+P mode showed maximum tensile strengths of 172 and 178 MPa,respectively.Hardness decreased at the interface and in the coarse dendrite and increased in the refined grain area.

Effect of interlayer cooling time on the temperature field of 5356-TIG wire arc additive manufacturing

In the paper, the finite element model(FEM) of wire arc additive manufacturing(WAAM) by TIG method was established by the ABAQUS soft, and the phase transformation latent heat was considered in the model. The evolution rules of temperature field at the interlayer with the cooling time of 10 s, 30 s and 50 s were obtained by the model. The WAAM experiment were performed by 5356 aluminum alloy welding wire with φ1.2 mm, and the simulated temperature field were varified by the thermocouple. The result shows that the highest temperature at the molten pool center increases with the increased interlayers at the same interlayer cooling time;the highest temperature drops gradually and the decline is smaller with the increased interlayer cooling time at the same layer. No remelting occurs at the top layer, and at least two remelting times occur in the other layers, resulting in complex temperature field evolution.

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.

Droplet-targeting laser hybrid indirect arc for additive manufacturing technology-A preliminary study

The contradiction between manufacturing accuracy and manufacturing efficiency is discussed in this paper.In order to solve this problem,a novel droplet-targeting laser hybrid indirect arc for additive manufacturing technology is proposed in which a couple of wires are melted using the alternating current with interwire indirect arc to achieve high deposition rate.On the other hand,droplets actively target the laser beam and detach from wire tip under the recoil pressure subjected to pulsed laser irradiating at desired position and with controlled mass for a precise bead forming.The process of alternative droplet growing at desired position are mathematically analyzed and then preliminary verified by experiment.By precisely controlling the wire feed speed and current frequency,the melting process at desired position and mass of wire is successfully obtained which is the fundamental for next-step for the droplet actively targeting laser.

Numerical analysis on the effect of process parameters on deposition geometry in wire arc additive manufacturing

Here we develop a two-dimensional numerical model of wire and arc additive manufacturing(WAAM)to determine the relationship between process parameters and deposition geometry,and to reveal the influence mechanism of process parameters on deposition geometry.From the predictive results,a higher wire feed rate matched with a higher current could generate a larger and hotter droplet,and thus transfer more thermal and kinetic energy into melt pool,which results in a wider and lower deposited layer with deeper penetration.Moreover,a higher preheat temperature could enlarge melt pool volume and thus enhance heat and mass convection along both axial and radial directions,which gives rise to a wider and higher deposited layer with deeper penetration.These findings offer theoretical guidelines for the acquirement of acceptable deposition shape and optimal deposition quality through adjusting process parameters in fabricating WAAM components.

Self-Adaptive Control System for Additive Manufacturing Using Double Electrode Micro Plasma Arc Welding

Wire arc additive manufacturing(WAAM)has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost.However,in the process of automatically manufacturing the high-quality metal parts by WAAM,several problems about the heat build-up,the deposit-path optimization,and the stability of the process parameters need to be well addressed.To overcome these issues,a new WAAM method based on the double electrode micro plasma arc welding(DE-MPAW)was designed.The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically.The effects between the parameters,wire feed rate and torch stand-off distance,in the process of WAAM were investigated experimentally.In addition,a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance.Finally,a series of tests were performed to evaluate the control system’s performance.The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system.Further,the deposition paths about the metal part’s layer heights in WAAM are simplified.Finally,the appearance of the WAAM-deposited metal layers is also improved with the use of the control system.

Microstructure and Mechanical Properties of Wire + Arc Additively Manufactured 2050 Al–Li Alloy Wall Deposits

Aluminum–Lithium(Al–Li) alloy is a topic of great interest owing to its high strength and light weight, but there are only a few applications of Al–Li alloy in wire ss, a special AA2050 Al–Li alloy + arc additive manufacturing(WAAM) process. To identify its feasibility in WAAM procewire was produced and employed in the production of straight-walled components, using a WAAM system based on variable polarity gas tungsten arc welding(VP-GTAW) process. The influence of post-deposited heat treatment on the microstructure and property of the deposit was investigated using optical micrographs(OM), scanning electron microscopy(SEM), X-ray diffraction(XRD), hardness and tensile properties tests. Results revealed that the microstructures of AA2050 aluminum deposits varied with their location layers. The upper layers consisted of fine equiaxed grains, while the bottom layer exhibited a coarse columnar structure. Mechanical properties witnessed a significant improvement after post-deposited heat treatment, with the average micro-hardness reaching 141 HV and the ultimate tensile strength exceeding 400 MPa. Fracture morphology exhibited a typical ductile fracture.

Formability,microstructure evolution and mechanical properties of wire arc additively manufactured AZ80M magnesium alloy using gas tungsten arc welding

Wire arc additive manufacturing(WAAM)technology has been used to fabricate the multi-layer single-pass deposited wall of AZ80M magnesium(Mg)alloy by gas tungsten arc welding.The formability,thermal cycles,microstructural evolution and mechanical properties of the WAAM AZ80M Mg alloy were investigated.The results show that there was significant difference in the temperature variation and the geometries between the original several layers and the subsequent deposited layers.Owing to the arc energy input,the interpass temperature rised rapidly and then stabilized at 150℃.As a result,the width of the deposited wall increased and then kept stable.There were obvious differences in the microstructure of the WAAM AZ80M Mg alloy among the top zone,intermediate zone and bottom zone of deposited wall.During the arc deposition process,theβphase of the WAAM AZ80M Mg alloy redissolved due to the cyclic heat accumulation,and then precipitated in the grain boundary.The cyclic heat accumulation also led to weakening of dendrite segregation.From the substrate to the top zone,the hardness of the deposited wall decreased gradually,and the intermediate zone which was the main body of deposited wall had relatively uniform hardness.The tensile properties of the WAAM AZ80M Mg alloy were different between the vertical direction and the horizontal direction.And the maximum ultimate tensile strength of the WAAM AZ80M Mg alloy was 308 MPa which was close to that of the as-extruded AZ80M Mg alloy.

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.