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Journal of Materials Processing Technology
Elsevie
Journal of Materials Processing Technology

Elsevie

0924-0136

Journal of Materials Processing Technology/Journal Journal of Materials Processing TechnologyISTPSCIEI
正式出版
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    Efficacy of elemental mixing of in situ alloyed Al-33wt%Cu during laser powder bed fusion

    Skelton, J. M.Sullivan, E. J.Fitz-Gerald, J. M.Floro, J. A....
    9页
    查看更多>>摘要：Challenges in developing novel alloys, specifically for use in laser powder bed fusion, may be overcome by in situ alloying of elemental powders during laser melting. This process could expedite prototyping of various alloy compositions and alleviate the restrictions and cost barriers of creating custom made alloy powder. In this research, the efficacy of in situ alloying is studied with respect to particle size distributions of the powder blends and the laser process parameters. The microstructure of the Al-Cu eutectic system is used here as an indicator of mixing quality of the constituent elements during laser melting of the particles. Hypo-or hypereutectic regions are readily visible through the dendritic growth of the alpha or theta phases, indicating regions where the solute con-centration deviates from the nominal eutectic composition. Samples were built from four powder blends at a range of scan speeds and powers to show how mixing is affected at different processing parameters. Image analysis and Vickers microhardness tests are both used to characterize the degree of mixing within the samples. Results of this study show that poor mixing can occur due to segregation of elemental powder within the powder blend. This produces local build compositions different than the mean powder composition when the mean particle volume is large enough that the melt pool encompasses too few particles to be a stochastic representation of the blend. Liquid phase intermixing limitations within the pool are thought to be less important than the melt pool volume itself.
      原文链接:
    • NSTL
    • Elsevier

    Failure behavior of resistance spot welded advanced high strength steel: The role of surface condition and initial microstructure

    Ghatei-Kalashami, A.Zhang, S.Shojaee, M.Goodwin, F....
    14页
    查看更多>>摘要：The continuous galvanizing process (CGP) under high dew point temperature has been recognized as a viable technique for improving the coating quality of advanced high-strength steels (AHSS). However, the effect of this surface modification technique on resistance spot welding (RSW) process is not clear. The aim of this study is to investigate the role of different surface conditions and initial microstructures obtained through CGP on me-chanical properties and failure behavior of resistance spot welded AHSS. It has been shown that the formation of internal oxides during the annealing and subsequent coating process reduced the heat input during RSW, resulting in smaller nugget size and consequently, lower tensile-shear peak load values. Finite element modeling (FEM) and experimental results indicated that in the case of the as-received sample, higher fusion zone/base-metal (FZ/BM) hardness ratio leads to a failure location closer to heat-affected zone (HAZ). However, the lower FZ/BM hardness ratio in the case of annealed-bare and annealed-coated specimens leads to failure location more towards FZ. It was shown that nugget size will not control the failure location during lap-shear loading but does affect nugget load-carrying capability. However, failure behavior is controlled by microstructural charac-teristics of different weld regions.
      原文链接:
    • NSTL
    • Elsevier

    Effects of interlayer metal on microstructures and mechanical properties of friction stir lap welded dissimilar joints of magnesium and aluminum alloys

    Peng, PaiWang, WenZhang, TingLiu, Qiang...
    11页
    查看更多>>摘要：The content of intermetallic compounds (IMCs) in friction stir lap welded (FSLW) dissimilar joints of Mg and Al alloys could be reduced by the addition of interlayer metal to improve the mechanical properties of the joints, while the underlying mechanism is still unclear. In this study, Cu and Ni powders are added as the interlayer materials into the FSLW joints of AZ31 Mg alloy and Al-Zn-Cu-Mg alloy, respectively. The types, sizes, and distributions of IMCs have been characterized, and the shear properties of the joints have been evaluated. Moreover, the mechanism underlying the influence of the interlayer metals on the evolution of IMCs in the joints and the effect of IMCs on the shear properties of the joints have been studied. The results showed that the order of phase formation in the joint without interlayer was Al12Mg17, Al3Mg2, MgZn2, CuMg2, Al2Cu, while the order of phase formation in the joint with added Cu interlayer was Al2Cu, CuMg2, AlCu, Al12Mg17, Al3Mg2, Cu5Zn8, and that in the joint with added Ni interlayer was Mg2Ni, Al3Ni, Al3Ni2, MgNi2, AlNi, Al12Mg17, Al3Mg2, MgZn2, Ni3Zn22, NiZn, Al2Cu. Due to the formed physical barrier and the mechanism of phase formation, the addition of interlayer metal effectively inhibited the formation of a Mg-Al phase. The bonding strengths between Mg-Cu, Al-Cu, Al-Ni, and Mg-Ni phases and matrix were higher than that between Mg-Al phase and matrix, which improved the shear properties of the joints with Cu and Ni interlayers.
      原文链接:
    • NSTL
    • Elsevier

    In situ X-ray and thermal imaging of refractory high entropy alloying during laser directed deposition

    Wang, HuiGould, BenjaminMoorehead, MichaelHaddad, Marwan...
    13页
    查看更多>>摘要：MoNbTiV high-entropy alloy was in situ alloyed with laser power-blown directed energy deposition additive manufacturing from a mixture of four elemental powders of Mo, Nb, Ti, and V. This study provides a fundamental understanding of the alloying process through in situ high-speed synchrotron X-ray imaging and infrared imaging. High-speed X-ray imaging was used to investigate the in situ alloying process through direct observation. The particle delivery velocities of four different elemental powders under the same processing conditions were studied to reveal the performance of the powders during the in situ alloying process. We found that the Ti and Nb powders showed the greatest and smallest averaged particle-delivery velocities among these four powders, respectively, and the particle delivery velocity would be affected by the particle characteristics, particle size, and density of powders. The velocities of the resulting melt pool flow were measured to show the melt flow dynamics in such a process. The residence time of each elemental powder was also obtained, and Mo powders showed the largest residence time followed by Nb, V, and Ti powders. The porosity induced by unmelted particles and entrapped gas occurred in the alloying process. The Mo powders resulted in the most unmelted particles, and the entrapped gas porosity was mainly induced by the keyhole fluctuation. With the assistance of an infrared camera, we reported the emissivity of the melt pool, the change of thermal properties, and melt pool morphology during alloying.
      原文链接:
    • NSTL
    • Elsevier

    Magnetic manipulation in directed energy deposition using a programmable solenoid

    Jackson-Crisp, AlexSegal, JoelClare, Adam T.Smith, Peter H....
    14页
    查看更多>>摘要：Laser directed energy deposition is useful for the manufacture and repair of aerospace components. Its inability to focus powder streams into narrow concentrations limits application for production of fine (<1 mm) features. In the case of magnetic feedstock materials, use of a magnetic field in the track vicinity can allow successful manipulation of track properties. In this work, a solenoid coaxially aligned to the laser beam is used to manipulate track dimensions and powder behaviour. A methodology is demonstrated which allows magnetic fields to dynamically manipulate processing conditions. An improvement to material efficiency of 25 % was achieved, and the effects of critical parameters were also examined. A solenoid fixed to a specific location along the toolpath was used to increase the cross-sectional area of tracks by up to 83 % in those positions. The placement of magnetic fields in the deposition zone were systematically investigated to better understand the mechanisms of powder incorporation. Magnetic manipulation of magnetic feedstocks in DED should therefore be considered as an adaptive control technique in cases where greater control of track dimensions or enhanced material feed control is required.
      原文链接:
    • NSTL
    • Elsevier

    Understanding the effect of scanning strategies on the microstructure and crystallographic texture of Ti-6Al-4V alloy manufactured by laser powder bed fusion

    Liu, JiangweiLi, GuichuanSun, QidongLi, Hu...
    11页
    查看更多>>摘要：In this work, experimental and numerical approaches are performed to explore the influence of scanning strategies on the microstructure, crystallographic texture as well as the mechanical behavior of Ti-6Al-4V alloy manufactured by Laser Powder Bed Fusion (LPBF). In-situ monitored data of the energy intensity show that different scanning strategies result in variations of energy intensity distribution. The characterization of the microstructure and crystallographic texture reveals that the sample with hexagon scan pattern displays the structure with columnar primary 13 phase, while the specimens with chessboard scan exhibit equiaxial-like morphology. EBSD and TEM results provide evidence of the appearance of residual 13 nanoparticles. A finite element model is developed to further explain the phase transformation during LPBF and the formation mechanism of residual 13 particles. The numerical results indicate that the appearance of the residual 13 phase is attributed to the preheating/reheating effect by the adjacent tracks and successive layers, and the final phase composition of the LPBF-built Ti-6Al-4V alloy combines the alpha ', alpha, and 13 phases. Findings in the present paper show that various scanning strategies lead to a clear diversification in the microstructure, crystallographic texture, and phase composition of LPBF-built samples, which opens a route towards the tailoring of mechanical properties and isotropic behaviors in additive manufacturing.
      原文链接:
    • NSTL
    • Elsevier

    Thermodynamically revealing the effect mechanism of Cu on the interfacial metallurgical reaction for Al/steel welding-brazing joint

    Yang, TaoDai, WeiChen, LongZhuang, Yuan...
    8页
    查看更多>>摘要：Developing excellent mechanical properties of Al/steel welding-brazing joint adding alloy elements for vehicle structure lightweight is in immediate need to reveal the effect mechanism of alloy elements on the interfacial metallurgical reaction. Here, the Al/steel welding-brazing joints with different Cu-coating thicknesses were designed to determine the effect rule of Cu on mechanical properties and interfacial microstructure evolution. More importantly, the action mechanism of Cu element on diffusion behavior of interfacial elements was clarified by synchrotron radiation light source and thermodynamic models. The results showed that appropriate Cu could improve the tensile strength of joints. And the Cu could efficiently inhibit the growth of interfacial brittle intermetallic compounds (IMCs) and the Fe diffusion into molten pool. Because the chemical potential of Fe in the molten pool increased with an increasing Cu content, which weakened the driving force of Fe diffusion. Besides, Cu and Al would react with each other to form Al2Cu with a lower Gibbs free energy under higher Cu content, which deteriorated the tensile strength of joints. Unambiguously, this work will deepen the understanding of the effect mechanism of Cu on the interfacial metallurgical reaction, which will be beneficial to the development and application of excellent properties of Al/Cu-coating/steel welding joints.
      原文链接:
    • NSTL
    • Elsevier

    A comprehensive investigation on the damage induced by the shearing process in DP780 steel

    Han, S.Chang, Y.Wang, C. Y.Dong, H....
    20页
    查看更多>>摘要：Sheared edge cracking phenomenon is a key problem limiting the application of high-strength steels. Therefore, it is very necessary to explore the cracking causes to promote the solution of this problem. In this paper, the damage in the sheared edge of DP780 steel is investigated by microstructure characterization, micro/macro mechanical property evaluation, and numerical simulation. Microvoids, microcracks, and work hardening behavior are identified as damage factors affecting the sheared edge cracking. Two types of microvoids are found based on the position of microvoids. Microvoids formed at phase interfaces have the characteristics of small size (<= 5 mu m) and large number (276-340), while microvoids generated from inclusions hold large size (> 5 mu m) and small number (6-18). The damage degree of microvoids is evaluated by number, size, and distribution. The result shows the damage of microvoids becomes more serious with the increasing shearing clearance. During shearing, microvoids are split to form microcracks. These microcracks become the cracking source in the subsequent process. Therefore, microcracks are the most crucial to the formability. Reducing microcracks is an effective method to avoid sheared edge cracking. Furthermore, the shearing process is simulated in ABAQUS. A VUSDFLD subroutine is developed for implementing the constitutive model of DP780 steel. The simulated results match the experiment results very well, which indicates the damage of DP780 steel during shearing can be predicted by simulations. The research of this paper is beneficial to understand the cause of sheared edge cracking and design an optimal shearing process.
      原文链接:
    • NSTL
    • Elsevier

    Time-dependent springback of high strength titanium tubular materials: Experiment and modeling

    Li, HengZhang, LiwenChen, GuangyaoMa, Jun...
    23页
    查看更多>>摘要：Although time-dependent springback is minor compared with instantaneous springback, its deformation-history dependent effects may deteriorates the compactness of parts assembly and poses potential hazards to the safety and stability of the equipment systems especially under harsh service conditions. However, time-dependent springback still has not been paid enough attention, and how to accurately predict this phenomenon is still a challenge needed to be solved urgently. In this work, taking high-strength Ti-3Al-2.5V titanium tubular materials (HSTT) upon bending as a case, the experimental exploration of the physical mechanisms and the prediction modeling for time-dependent springback of the HSTT were conducted. First, the residual stress and dislocation evolution of HSTT during bending, instantaneous springback and time-dependent springback are comprehensively experimentally obtained, and the compression-tension uneven residual stress-driven creep deformation mechanism of time-dependent springback for HSTT was revealed. Then, considering stress attenuation, a Viscoelastic-Kelvin constitutive model for time-dependent springback was developed and combined with the stress invariant-based model (SIM) and Chord modulus model to accurately predict the whole process of bending, instantaneous springback and time-dependent springback of the HSTT. Finally, the verified model is employed to explore the evolution rules of time-dependent springback and residual stress of HSTT upon bending, and the deformation-history dependent effects of time-dependent springback for spatial multi-bending component are clarified. The findings and methods of this study could aid in achieving higher precision manufacturing of high performance tubular components.
      原文链接:
    • NSTL
    • Elsevier

    Study on surface integrity of titanium alloy machined by electrical discharge-assisted milling

    Xu, MoranLi, ChangpingKurniawan, RendiPark, GunChul...
    12页
    查看更多>>摘要：Electrical discharge-assisted milling (EDAM) is an efficient machining process for titanium alloys according to previous studies. However, a complete understanding of the surface integrity of titanium alloy machined with EDAM is not yet sufficient. Therefore, in this paper, surface defects such as chip layer adhesion, debris, feed marks, and burrs were investigated and identified. Among them, the adhesion of the chip layer is the most common surface defect and is the factor that has the greatest influence on the surface quality. In addition, surface roughness, micro-hardness, and residual stress were analyzed and discussed. The results show that the surface roughness of EDAM is significantly improved compared to conventional milling (CM). Also, the residual stress generated by EDAM is much smaller than that of CM, and the main type of residual stress is residual compressive stress. Similarly, the surface microhardness after EDAM is also slightly smaller than that of CM. This increased surface integrity is due to the material softening effect due to the heat generated by the discharge spark. Consequently, EDAM is a good candidate method for efficient machining of titanium alloys.
      原文链接:
    • NSTL
    • Elsevier