Solidification Microstructure Evolution Research Articles

Inhibiting cracking and improving strength-ductility for laser powder bed fusion René 104 superalloy by Sc and Y microalloying

Cracking is a critical challenge for the application of additive manufacturing (AM) for producing Nickel-based superalloys with high volume fraction γ′ phase. This study systematically investigated the effects of alloying elements (Sc, Y) on the cracking susceptibility and microstructure of René 104ScY superalloy fabricated by laser powder bed fusion. The effects of Sc and Y elements on solidification behavior, microstructure evolution and crack inhibition were discussed. The results show that the nano-Al3(Sc, Y) phases in René 104ScY superalloy refine both grain and cellular structure sizes, triggering the columnar-to-equiaxed transition, and efficiently inhibiting crack generation. The formation of dislocation substructures, stacking faults and Lomer-Cottrell locks are responsible for the synergistic enhancement in strength-ductility of René 104ScY superalloy. Crack-free René 104ScY superalloy with excellent strength-ductility synergy was obtained by Sc and Y microalloying. These results provide a novel approach to developing crack-free Nickel-based superalloys for AM and offer insights for addressing high cracking susceptibility in other alloys.

Strengthening synergies of various interlayers in NiTi toTi6Al4V dissimilar laser joints

A sound NiTi-Ti6Al4V dissimilar joint featuring NiTi's superelasticity is crucial for merging both material benefits in aerospace and biomedical fields. Yet, the solidification of excessive intermetallic compounds (IMCs) for dissimilar par, notably Ti2Ni, poses a considerable risk of severe brittleness. Altering the chemistry of the fusion zone (FZ) could prevent embrittlement and enhance the mechanical performance of the joints. In this regard, understanding the impact of filler materials on the solidification behavior is vital. This study unveils the synergistic impact of employing these diverse interlayers, characterized by varying melting points, metallurgical compatibilities, and reaction spontaneity, on solidification behavior, microstructure evolution, and mechanical properties and presents a viable approach to enhance the microstructure and performance of NiTi and Ti6Al4V joints. A notable improvement in properties was observed in the Pd-interlayered joint, where the strong reaction spontaneity in the Ti-Pd system facilitated the preferential solidification of the TiPd phase in the FZ. This significantly reduced the amount of detrimental Ti2Ni IMC, ultimately decreasing joint embrittlement. Mechanical testing data demonstrated a progression in performance in the following sequence: interlayer-free, Co-interlayered, Zr-interlayered, and Pd-interlayered. Using interlayer materials that form lower-energy compounds with Ti and offer good mechanical properties, such as TiPd in this study, is presented as an optimal approach to enhance joint mechanical properties. The present work advances the metallurgical knowledge associated with non-equilibrium processing of NiTi and Ti6Al4V alloys.

Solidification Behavior and Microstructure Evolution in Dissimilar Electron Beam Welds Between Commercially Pure Iron and Nickel

Electron beam welding processes have highly accurate control of both spatial and temporal heating profiles which provide unique capabilities in dissimilar metals joining. In this work, electron beam welds were made between commercially pure nickel and iron to determine the effect of fusion zone composition on solidification behavior and microstructure evolution. The weld was made with a beam deflected in a circular pattern to enable joining and promote mixing. The beam traveled at a shallow angle of approximately 1 deg to the joint interface starting in the nickel and finishing in the iron. The shallow angle created a weld with a composition gradient along its 110 mm length. The solidification behavior and final weld microstructure were characterized using both light optical microscopy and scanning electron microscopy. Electron backscatter diffraction was used to determine the phase fractions in the fusion zone. A change in solidification mode from face-centered cubic austenite to body-centered cubic ferrite was observed as a function of fusion zone composition. Weld cross-sections containing 65.5 wt pct Fe and 76.9 wt pct Fe had a two-phase fcc + bcc microstructure. Using the compositions and phase fractions, the two-phase region was estimated to be between 56.4 and 79.7 wt pct Fe. Martensite was observed in cross-sections containing between 76.9 wt pct Fe and 98.1 wt pct Fe, which was confirmed using hardness measurements.

Simulation and Experimental Study on the Effect of Superheat on Solidification Microstructure Evolution of Billet in Continuous Casting.

The control of the solidification structure of a casting billet is directly correlated with the quality of steel. Variations in superheat can influence the transition from columnar crystals to equiaxed crystals during the solidification process, subsequently impacting the final solidification structure of the billet. In this study, a model of microstructure evolution during billet solidification was established by combining simulation and experiment, and the dendrite growth microstructure evolution during billet solidification under different superheat was studied. The results show that when the superheat is 60 K, the complete solidification time of the casting billet from the end of the 50 mm section is 252 s, when the superheat is 40 K, the complete solidification time of the casting billet is 250 s, and when the superheat is 20 K, the complete solidification time of the casting billet is 245 s. When the superheat is 20 K, the proportion of the equiaxed crystal region is higher-the highest value is 53.35%-and the average grain radius is 0.84556 mm. The proportion of the equiaxed crystal region decreases with the increase of superheat. When the superheat is 60 K, the proportion of the equiaxed crystal region is the lowest-the lowest value is 46.27%-and the average grain radius is 1.07653 mm. Proper reduction of superheat can obviously reduce the size of equiaxed crystal, expand the area of equiaxed crystal and improve the quality of casting billet.

Effect of mold temperature on the solidification process and microstructure of Zr-based metallic glasses during casting

To explore the relationship between mold temperature and the formation of large-size metallic glasses, the influence of mold temperature on the solidification process and microstructure evolution of amorphous melts was investigated. It was found that increasing the mold temperature to 623 K contributes to improving the solidification time from ∼1.79 s to ∼2.32 s without affecting the solidification behavior of amorphous melt. However, the duration of the supercooled liquid state was prolonged by the excessively high mold temperature, resulting in a considerable increase in the glass transition time from ∼12.78 s to ∼145.7 s and a decline in the cooling rate from 27.6 K/s to 2.1 K/s, which ultimately leads to the crystallization of the sample. In addition, it has been observed that the 573 K mold temperature is not only the optimal mold temperature to ensure the amorphous nature of the sample but is also beneficial to improve the internal temperature gradient of the sample, thereby reducing the risk of deformation or cracking. Appropriate control of mold temperature can provide valuable guidance for large-size amorphous castings and associated process parameters.

Microstructure Evolution of Gas-Atomized β-Solidifying γ-TiAl Alloy Powder during Subsequent Heat Treatment

To promote the use of γ-TiAl alloys in various domains, such as the aerospace industry, it is pivotal to investigate the unusual phase transformation from rapidly solidified and metastable γ-TiAl toward the equilibrium state. In this study, the microstructure characteristics of gas-atomized β-solidifying Ti-44Al-6Nb-1.2Cr alloy powder, in terms of the effect of rapid solidification on microstructure evolution, were explored in comparison with cast materials. The phase constitution, morphology, and crystallographic orientation between phases were noted to be distinct. Furthermore, subsequent heat treatment was conducted at different temperatures using gas-atomized powder. The transition from the metastable to equilibrium state was observed, wherein firstly, the γ phase precipitated from the retained α2 phase, forming an α2/γ lamellar microstructure. In intensified heat-treatment conditions adequate for cellular reaction, β/γ cells were formed at the grain boundaries of α2/γ lamellar colonies. The findings highlight the overall phase transformation during rapid solidification and continuous microstructural evolution from the nonequilibrium to the equilibrium state. This research can bridge the gap in understanding the effect of the solidification rate on microstructural evolution and contribute to enhanced comprehension of the microstructure in other domains involving rapid solidification, such as the additive manufacturing of γ-TiAl alloys.

Relationship between solidification path, microstructure evolution and solidification cracking behavior of Mg-Al-Ca alloy during TIG welding

The high-strength and creep-resistant Mg-Al-Ca-Mn alloys have broad application prospects. However, solidification cracking occurs in these alloys in certain conditions and the origin is still unclear. This work investigated the relationship between the solidification path, microstructure evolution and solidification cracking behavior of the Mg-xAl-2Ca-Mn alloys during tungsten inert gas (TIG) welding. Results show that when the fusion zone's Ca/Al mass ratio ranges from 0.4 to 1.64, solidification cracking occurs at a Ca/Al mass ratio of ∼0.7. As the Ca/Al mass ratio approaches this value, the grain size increases, and the Laves phases are reduced gradually. The early formed Laves phases play an important role in promoting dendrite segmentation, refining grain size and enhancing grain boundaries. When a solidification path delays the formation of Laves phases, the Laves phases will be reduced accompanied by grain coarsening. In such a solidifying microstructure, intergranular cavitation is easy to occur, and the resistance of the semi-solid alloy to crack propagation is severely reduced.

Transmission electron microscopy of the rapid solidification microstructure evolution and solidification interface velocity determination in hypereutectic Al-20at.%Cu after laser melting

The evolution of rapid solidification (RS) microstructure and solidification interface velocity has been studied experimentally by in-situ transmission electron microscopy and postmortem characterization for hypereutectic Al-20at.%Cu (37 wt.%Cu) after laser melting. Four morphologically distinct regions formed via growth modes changing from θ-Al2Cu phase dendrites to eutectic cell growth, possibly α-Al dendrite growth (α-cell), banded growth, and α-Al plane front growth. Tendency for faceting and low capacity for solute trapping limited the θ-phase dendrite growth to solidification interface velocity v < 0.07 m/s. Consequently, formation of pro-eutectic micro-constituent was suppressed, and RS microstructure formation was dominated by eutectic, α-cell, and banded morphology grains for the Al-20at.%Cu alloy. Eutectic growth operated for interface velocity of 0.1 m/s ≤ v < 0.3 m/s, with a transition from regular lamellar, 2-λ and 1-λ mode to a dense irregular morphology dominated by α-phase at v = 0.3 m/s. Interface temperature calculations indicated feasibility of α-cell growth mode for 0.3 m/s ≤ v < 0.7 m/s. Banded growth occurred for 0.7 m/s ≤ v < 1.3 m/s. Plane front α-phase growth was evident for interface velocities v ≥ 1.3 m/s. Previous work on rapid solidification microstructure development in hypereutectic Al-Cu alloys reported a regime of α-cell growth subsequently to eutectic and prior to transition to banded growth for Al-19at.%Cu (36 wt.%Cu), while for Al-22at.%Cu (40 wt.%Cu) eutectic growth transitioned directly to α-plane front growth without emergence of a banded regime. Based on the current study the disappearance of the banded growth regime occurs for a composition larger than 20at.%Cu.

Development of process-structure linkage for Inconel 718 processed by laser powder bed fusion: a numerical modeling approach

PurposeUnderstanding and tailoring the solidification characteristics and microstructure evolution in as-built parts fabricated by laser powder bed fusion (LPBF) is crucial as they influence the final properties. Experimental approaches to address this issue are time and capital-intensive. This study aims to develop an efficient numerical modeling approach to develop the process–structure (P-S) linkage for LPBF-processed Inconel 718.Design/methodology/approachIn this study, a numerical approach based on the finite element method and cellular automata was used to model the multilayer, multitrack LPBF build for predicting the solidification characteristics (thermal gradient G and solidification rate R) and the average grain size. Validations from published experimental studies were also carried out to ensure the reliability of the proposed numerical approach. Furthermore, microstructure simulations were used to develop P-S linkage by evaluating the effects of key LPBF process parameters on G × R, G/R and average grain size. A solidification or G-R map was also developed to comprehend the P-S linkage.FindingsIt was concluded from the developed G-R map that low laser power and high scan speed will result in a finer microstructure due to an increase in G × R, but due to a decrease in G/R, columnar characteristics are also reduced. Moreover, increasing the layer thickness and decreasing the hatch spacing lowers the G × R, raises the G/R and generates a coarse columnar microstructure.Originality/valueThe proposed numerical modeling approach was used to parametrically investigate the effect of LPBF parameters on the resulting microstructure. A G-R map was also developed that enables the tailoring of the as-built LPBF microstructure through solidification characteristics by tuning the process parameters.

The Role of Boron Addition on Solidification Behavior and Microstructural Evolution of a High Niobium-Containing TiAl Alloy

This work investigates the role of boron addition in the solidification behavior and microstructural evolution during the heat treatment process of Ti-46Al-8Nb-xB (x = 0.1, 0.7, 1.4, 2.5 at.%). The results show that the solid solution boron element prefers to occupy the interstitial vacancies of the α2 phase in the alloy. However, the solid solubility of the boron element in high Nb-containing TiAl alloys is extremely low. Therefore, it does not have a significant effect on the lattice distortion of α2 and γ phases in the alloy. When the boron content is added up to 0.1%, a B27-type TiB precipitated phase is produced in the alloy. The morphology of borides mostly shows short rod-like structures, and a few show long curved shapes. And the addition of boron refines both the alloy colony size and the lamellar structure. Furthermore, it is also found that boron addition weakens the casting texture of the alloy. After a solid solution and different time aging heat treatment process, the microstructure of different boron content alloys have experienced obvious coarsening phenomenon. However, the morphology of the boride is closely related to boron content and heat treatment.

A multiphase modeling for investigating temperature history, flow field and solidification microstructure evolution of FeCoNiCrTi coating by laser cladding

In this work, a multiphase numerical model was established to investigate the non-isothermal flow and microstructure evolution during laser cladding. The model considered the beam-powder interaction, temperature dependent material properties, the effect of buoyancy and surface tension on convection. The accuracy of the model was verified comparing the simulated coating geometric morphology with the experimental results. Simulation indicated that the temperature and flow of the molten pool were interactive and mutually causal. On the one hand, the temperature field affected the tension gradient and the liquid flow direction. On the other hand, the velocity field significantly affected the heat transfer in the molten pool. Specifically, the maximum fluid velocity was 9.58 mm/s and the Peclet number (PeT) value was less than 5 at the initial stage, indicating that conduction dominated in heat transfer. Furthermore, the PeT value was greater than 200 when the maximum velocity reached 344 mm/s. The heat transfer in the molten pool was mainly thermal convection. In addition, the distribution diagram of solidification parameters (G and R) was calculated to quantitatively establish the internal correlation between solidification parameters and microstructure combing with experimental observation, and revealed the columnar-to-equiaxed transition (CET). Eventually, the microhardness results showed that HEA coating could improve the Ti6Al4V surface microhardness. Simultaneously, the CET behavior significantly affected the microhardness of the coating.

Simulation of solidification microstructure evolution of 316L stainless steel fabricated by selective laser melting using a coupled model of smooth particle hydrodynamics and cellular automata

Selective Laser Melting (SLM) is an efficient and advanced manufacturing technology that utilizes lasers to melt and solidify metal or alloy powders, layer by layer, to form the desired object shape. This study aims to investigate the evolution behavior of the solidification microstructure during the SLM process and presents a novel numerical simulation method based on the Smoothed Particle Hydrodynamics-Cellular Automaton (SPH-CA) coupling model. The SPH-CA coupling model combines the particle information, such as position and temperature, from Smoothed Particle Hydrodynamics (SPH) with the Cellular Automaton (CA) method in a one-way coupling manner, enabling simultaneous computation of multiple physical fields, including heat transfer, melting, solidification, and morphology. This model addresses challenges that are difficult to handle in grid-based computations, such as free surface variations, boundary deformations, interfacial motion, and large deformations. Additionally, it effectively simulates the morphology of the solidification microstructure. Furthermore, the coupling process performs kernel function weighted calculations at the same scale, which results in higher accuracy compared to the grid-based multiscale mapping. The simulation results demonstrate that different processing parameters influence the morphology of the molten pool and the thermal undercooling, thereby affecting the growth characteristics of the grains. A higher laser scanning speed leads to smaller molten pool size, finer grain sizes in the solidification microstructure, larger laser grain angles, and a higher content of columnar grains. These findings are consistent with experimental observations and existing conclusions, providing evidence for the feasibility and effectiveness of the proposed model in the context of SLM.

The Effects of Cooling Rate on Microstructure Formation during Solidification of 319 Alloy

This work assesses the effect of cooling rate (T˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{T}$$\\end{document}) on the solidification kinetics and microstructural evolution of a 319 aluminum alloy with and without the addition of Al–5 wt%Ti–1wt%B grain refiner. Directionally solidified samples were produced under various cooling rates (from 0.05 to 40 °C/s). Microstructure coarsening was then quantitatively analyzed by measuring grain size (GS) and primary (λ1), secondary (λ2) and average (λL) dendrite arm spacing. The results show that polarized optical images can be used to identify dendrite fragments between neighboring primary dendrites, allowing a more accurate microstructural analysis after the addition of grain refiner. The results also show that, for a given T˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{T}$$\\end{document}, although GS is reduced after the addition of grain refiner, the respective values of λ1, λ2 and λL remain practically the same. In other words, the grain refiner only affects nucleation and not grain growth. Experimental growth equations are proposed to represent this behavior. Furthermore, λL is shown to be a good parameter for evaluating microstructural refinement.

Comparison of Solidification Microstructure Evolution of Al-10Si and Recycled Aluminium Beverage Can Strips Made in a Strip Caster

A strip caster was used to cast two types of aluminium alloys: an almost eutectic Al-Si alloy (Al 10 Si) with contaminants of 0.6 Fe, 0.2 Pb, and 1.4 Sn, which exhibits a polyphase microstructure upon solidification, and recycled aluminium beverage cans made from Al 0.8 Mn alloy containing 0.4 Si, 0.5 Fe, and 0.1 Mg, which has a monophase microstructure upon solidification. The molten materials were poured at 650 oC (Al 10 Si) and 670 oC (Al 0.8 Mn, 0.4 Si, 0.5 Fe, 0.1 Mg) on a cooling slope specially designed to obtain a semisolid material. This semisolid material was then dragged between rolls at a rate of 0.2 m/s to obtain high-quality metal strips. There was less eutectic modification with larger Al-α grains in the middle region of the sheet between the fine eutectic layers, indicating a lower cooling rate. However, during the recycling of aluminium beverage cans, large grains were formed with a columnar structure at the interface of the rolls, and semisolid melts with cracks were formed between the columnar grain boundaries owing to the compression of the rolls. The middle of these grains contained smaller equiaxial grains that were subjected to dragging. The as-cast specimens were submitted to homogenisation heat treatment at 560 oC for a period of 10 h and cooled to room temperature before being cold rolled (Temper H18) and recrystallised (Temper O) to examine the effect of these treatments on the tensile mechanical properties. During cold rolling (Temper H-18), grain alignment occurred with a yield stress, maximum stress, and elongation of 209.5 MPa, 210.1 MPa, and 2.8%, respectively. The strength decreased (yield stress of 58 MPa and maximum stress of 120.2 MPa) under recrystallisation conditions (Temper O), but the ductility increased (8.9%). This is in contrast to the Al-Si (Al 10Si) strip, which exhibited a yield stress, maximum stress, and elongation of 103.3 MPa, 128.7 MPa, and 1.9%, respectively. The A1 10Si strips also fractured during cold rolling, indicating high material fragility.

H13 tool steel fabricated by wire arc additive manufacturing: Solidification mode, microstructure evolution mechanism and mechanical properties

The critical application value of AISI H13 tool steel in the die and mold industry and the great application potential of additive manufacturing (AM) technology in die manufacturing and repair have attracted extensive attention from researchers. However, there is no consensus on the solidification mode and microstructure evolution mechanism of H13 during AM. The relationship between the unique cellular/dendritic substructures and the grain structures in AM-fabricated H13 components has yet to be fully understood. This work focused on the microstructure and mechanical properties of different regions of the H13 component manufactured by wire arc additive manufacturing technology. Thermodynamic calculations and experimental results confirmed the formation of δ-ferrite during the non-equilibrium solidification of AM. The cellular/dendritic substructure is caused by the solidification of δ-ferrite and austenite together with the accompanying segregation. The results of optical microscopy and scanning electron microscopy, as well as the reconstructed prior austenite grain structure by electron backscatter diffraction (EBSD) all confirmed that the formation and distribution of cellular/dendritic substructures were not directly related to the prior austenite grain. The EBSD pole figures show that although the martensite transformation weakened the preferred orientation of crystals, the martensite phase in the typical structure of the deposition area still had a high texture strength, which may be the main reason for the anisotropic mechanical properties of the H13 component.

Microstructural evolution and precipitated phase characteristics in the fusion zone for the as-repaired Inconel 718 alloy by directed energy deposition additive manufacturing

In this study, five laser powers were employed to repair Inconel 718 alloy by directed energy deposition additive manufacturing technology. Under various solidification conditions, microstructural evolution and precipitated phase characteristics in the fusion zone (FZ) of the as-repaired Inconel 718 specimens were investigated. The results showed that the main dendritic morphology in the FZ changes from equiaxed dendrites to columnar dendrites with increasing laser power, accompanied with the morphological evolution of numerous Laves phases from a long-chained shape to a blocky shape. However, these morphological changes for the Laves phase are not only relevant to the solidification structure characteristics but also affected by the repetitive vertical thermal cycles induced by layer-by-layer deposition because multiple thermal cycles could be regarded as conducting mild heat treatment to the FZ microstructure. On the one hand, the gradually increasing heat accumulation effects are conducive to partially dissolving Laves phase with increasing laser power; on the other hand, there are a number of γ′′ phase, γ′ phase and δ phases precipitated in the Nb-rich zone. When laser power is 1400 W, the volume fraction of the Laves + δ phases is the highest but the volume fraction of the γ′ + γ′′ phases is the lowest among the five as-repaired specimens, resulting in the lowest micro-hardness.

Modelling of the Solidifying Microstructure of Inconel 718: Quasi-Binary Approximation

The prediction of the equilibrium and metastable morphologies during the solidification of Ni-based superalloys on the mesoscopic scale can be performed using phase-field modeling. In the present paper, we apply the phase-field model to simulate the evolution of solidification microstructures depending on undercooling in a quasi-binary approximation. The results of modeling are compared with experimental data obtained on samples of the alloy Inconel 718 (IN718) processed using the electromagnetic leviatation (EML) technique. The final microstructure, concentration profiles of niobium, and the interface-velocity–undercooling relationship predicted by the phase field modeling are in good agreement with the experimental findings. The simulated microstructures and concentration fields can be used as inputs for the simulation of the precipitation of secondary phases.

Crack inhibition to enhance strength-ductility of CM247LC alloy fabricated by laser powder bed fusion

High cracking susceptibility is a critical challenge for the application of high γ′-fraction Ni-base superalloys fabricated by laser powder bed fusion (LPBF). This study systematically investigated the effect of process parameters on the cracking susceptibility and microstructure of LPBF-processed CM247LC alloy. The formation mechanisms of liquation cracks and solidification cracks were revealed. The effects of process parameters on solidification behavior, microstructure evolution and local strain level were discussed. The cracking behavior was significantly affected by the high-angle grain boundaries (HAGBs), elemental segregations (e.g., C and O) and stress concentration at cracking regions. An increase in the laser power increased the length of mushy zone and the depth/width ratio of melt pools, resulting in high solidification cracking susceptibility. The overlap between adjacent melt tracks determined by hatch spacing and layer thickness could heal partial cracks through remelting. Nearly crack-free CM247LC samples with enhanced strength-ductility (yield strength of 921 ± 38 MPa, ultimate tensile strength of 1278 ± 3 MPa, and elongation of 16.1 ± 1.3%) were obtained by optimized process parameters. The zigzag grain boundaries, refined grains and reduced grain aspect ratio in the nearly crack-free samples could relieve the stress concentration along the grain boundaries and enhance the bonding of adjacent grains and thus delay the propagation of cracks. This work may provide essential comprehension for improving the LPBF processability of high γ′-fraction Ni-base superalloys.

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 important application prospects in realizing structural lightweight and vibration reduction. However, their engineering application is greatly limited by poor plastic formability. Wire and arc additive manufacturing (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 correlations 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 properties and damping capacities are mainly attributed to the weakened basal texture with a relatively high Schmid factor for basal <a> slip, 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.

A 3D Multiscale Model for Prediction of the Microstructure Evolution in Ti6Al4V Components Produced by Laser Powder Bed Fusion

A transient 3D multiscale model has been created to simulate the evolution of solidification microstructures rapidly and effectively in Ti6Al4V parts produced through Laser Powder Bed Fusion (LPBF). The microstructure simulation tool has been enhanced to account for rapid solidification conditions in Ti6Al4V alloys during processing of multi-layer multi-track LPBF parts. The simulation tool can evaluate the impact of part geometry, lase power input, laser speed, and laser beam shape on the formation of the microstructure in LPBF-processed Ti6Al4V alloy. The multiscale model considers several factors, including preferential crystallographic growth direction, isomorphism, epitaxy, melt pool motion, and temperature gradients to generate the observed texture and morphology of the microstructure in Ti6Al4V components. The model can evaluate various microstructure characteristics, such as grain size and texture. Consequently, it could aid in controlling the formation of solidification microstructures in Additive Manufacturing (AM) processed parts. The simulation tool has been previously validated by using IN625 laser remelting experiments made by National Institute of Standards and Technology. The 3D simulation tool can also be utilized to predict the microstructure formation in Ti6Al4V components produced by the Electron Beam AM processes.