Solidification Parameters Research Articles

Numerical Simulation and Experimental Studies of Gas Pressure Infiltration Al-356/SiC Composites

In this study, the filling process, solidification parameters, temperature distribution, and residual stress distribution of gas pressure-infiltrated Al-356/SiC composites were investigated through simulation and experiment. In addition, a series of orthogonal tests was also carried out to precisely demonstrate the preheating temperature, infiltration temperature, and infiltration pressure. After a thorough analysis, the orthogonal tests revealed that the optimal process parameters are as follows: the SiC preheating temperature is 550 °C, the infiltration temperature of the Al-356 alloy is 620 °C, and the infiltration pressure is 8 MPa. The simulation results revealed that pressure had a sharp decrease of ~87% during filling, and the critical pressure was ~0.12 MPa. The velocity decreased with the increase in the filling time, and the average velocity was ~2.60 ms−1. Feasible analysis suggested that critical pressure is ~0.11 MPa and average velocity is ~4.20 ms−1; this difference is attributed to apparent velocity and the Kozeny constant. In the solidification process, shrinkage porosity appeared in the centers of the composites, which is evident with scanning electron microscopy. Moreover, the stress concentration of 171.3 MPa appeared in the composite region connected with the runner, which is the cause of the nucleation of the crack. However, based on the optimum orthogonal parameters and simulative results, the stress concentration was reduced, and crack-free and porosity-free composites were achieved.

Gradient-controlled freeze casting of preceramic polymers

Solidification is the foundation upon which freeze casting is built, and this work seeks to understand the solidification process in freeze casting, especially with respect to the growth of dendrites. To this end, two solidification parameters, freezing front velocity and temperature gradient, were independently controlled using a gradient-controlled freeze casting setup to investigate the effects of each parameter. Changes in dendritic pore size and morphology with solidification parameters were investigated by scanning electron microscopy and mercury intrusion porosimetry. The results agree with dendrite growth theory. The theory of constitutional supercooling is used to describe the morphological changes of dendritic pores to cellular pores by the control of freezing front velocity, temperature gradient, and preceramic polymer concentrations.

Numerical and experimental investigation of the thermal behavior and microstructure of wire arc additive manufactured 316L stainless steel straight wall part

The heat transfer behavior during wire arc additive manufacturing is closely related to the dimensional accuracy and performance of the formed part. To investigate the thermal behavior of stainless steel 316L straight wall part fabricated by the wire arc additive manufacturing process, a three-dimensional transient finite element model is established based on the double elliptic heat source model. At the same time, the temperature measurement experiment on the characteristic position of the substrate is carried out. The thermal cycle curve obtained by the finite element model is in good agreement with the measured result. By analyzing the simulation results, the finite element model established can effectively reveal the thermal behaviors such as melting, solidification, heat accumulation and remelting during the forming process of the straight wall part. In addition, the solidification parameters obtained by the model are correlated with the microstructure. High G/R induces the production of cellular crystals and columnar dendrites, on the contrary, the formation of equiaxial crystals, which provide guidance for the prediction of the morphology of the microstructure.

A thermal field FEM of titanium alloy coating on low-carbon steel by laser cladding with experimental validation

Numerical simulation is an efficient method to study the laser cladding process via reconstructing the thermal field and analyzing the evolution of the microstructures. In this work, a novel 3D finite element model (FEM) of the laser cladding process is proposed for materials with significantly different thermo-physical properties, for example, a titanium alloy (TA1) coating on an iron (Q235) substrate. Multiple practical factors, like the coating geometry variation, powder preheating and laser energy attenuation, were considered in this model to ensure its high accuracy. For different laser scanning speeds, the transient temperature contours and their variations against time were simulated, and the calculation errors of the highest temperatures are <2 %. Based on the comparison of the binary phase (TiFe) diagram with the chemical composition of the coating, a new criterion, called the Tm criterion, was established for the coating solidification. Then, the solidification parameters of the moving solid-liquid interface, like the cooling rate, solidification rate and G/R (temperature gradient to solidification rate) ratio, were calculated to predict and analyze the solidification process and microstructure evolution of the coating. Finally, the simulation results were compared with the physical experiments, which proved the validity of the FEM and the rationality of the Tm criterion. Based on the numerical simulation and predicted microstructure evolution, this research provides an accurate, applicable and powerful analytical method for the laser cladding process with different materials, which can substantially improve the time and cost efficiencies of the process optimization.

Microstructure engineering during directed energy deposition of Al-0.5Sc-0.5Si using heated build platform

Achieving a specific solidification morphology during the directed energy deposition process can be key to desired properties of the deposited part. The careful control of thermal gradient and cooling rates can be utilized to achieve these grain morphologies. The heating of the build platform and post-deposition heat treatment are two ways in which we have shown to control these solidification parameters. Three-dimensional heat transfer and material flow model along with columnar-to-equiaxed transition diagram have been used to model the process and the microstructure evolution during laser directed energy deposition of Al-0.5Sc-0.5Si powder. The computed results have been validated using the experimentally measured thermal cycles and melt pool shape and sizes. The computed thermal gradient and cooling rates are used to predict the solidification morphology compared with the experimentally observed microstructure. For a specific set of deposition parameters, the fraction of equiaxed grains is least in the bottom layers, highest in the middle layers, and reduced in the top layer. The increasing build platform temperature increases the fraction of equiaxed grains in any specific deposited layer. The microhardness of various layers in different specimens as a function of build platform temperature is also shown to be a function of the solidification microstructure. The developed and validated numerical model is able to predict the microstructure evolution and can be a tool for further microstructure engineering during the L-DED process.

Calibrating uncertain parameters in melt pool simulations of additive manufacturing

Melt pool scale numerical modeling of additive manufacturing (AM) processes can provide predictive capabilities and theoretical insight into the process-property-structure-performance relationships for AM parts. Despite capabilities of numerical models to solve complex multi-physics problems, it is often important to consider a tradeoff between detailed physics and computational cost. Therefore, sources of uncertainty in both experimental conditions and the parameters needed for modeling require models to be validated against empirical evidence. Here, a method is proposed to calibrate uncertain parameters used in continuum-scale melt pool models for powder bed fusion (PBF) AM. Both a simplified heat transfer model and a heat transfer and fluid flow model were investigated. A surrogate model and Markov chain-based optimization algorithm calibrated melt pool geometry for models within experimental variation of the target melt pool width and depth from the NIST AM-Bench 2018-02 dataset. The melt pool temperature distributions, solidification parameters, and simulated multi-layer solidification microstructures were compared between the two models. Similar results from both models indicate that calibrated, lower fidelity numerical models may be used in place of higher fidelity models to generate melt pool solidification data. These calibrated models therefore enable lower computational cost melt pool simulations without a noticeable decrease in simulation accuracy for grain-scale microstructure simulations.

Macrosegregation Evolution in Eutectic Al-Si Alloy under the Influence of a Rotational Magnetic Field

Using magnetic stirring during solidification provides a good opportunity to control the microstructure of alloys, thus controlling their physical properties. However, magnetic stirring is often accompanied by a change in local concentrations, and new structures form which could harm the physical properties. This research paper investigated the effect of forced melt flow by a rotating magnetic field (RMF) on the macrostructure of an Al-Si eutectic alloy. To serve this purpose, Al-12.6 wt% Si alloy samples were solidified in a vertical Bridgman-type furnace equipped with a rotating magnetic inductor to induce the flow in the melt. The diameter and length of the sample are 8 mm and 120 mm, respectively. The solidification parameters are a temperature gradient (G) of 6 K/m, and the solid/liquid front velocity (v) of 0.1 mm/s. These samples were divided into parts during the solidification process, where some of these parts are solidified under the effect of RMF stirring while others are solidified without stirring. The structure obtained after solidification showed a distinct impact of stirring by RMF; new phases have been solidified which were not originally present in the structure before stirring. Besides the eutectic structure, the new phases are the primary aluminum and the primary silicon. The Si concentration and the volume fraction of each phase were measured using Energy-Dispersive Spectroscope (EDS)and new image processing techniques. The experimental results reveal that applying the RMF during the solidification has a distinct effect on the macrostructure of Al-Si eutectic alloys. Indeed, the RMF provokes macro-segregation, reduces the amount of eutectic structure, and changes the sample’s Si concentration distribution.

A calculation method of solidification parameter threshold for welding microstructure evolution

The relationship between the evolution of microstructure morphology (planar, cellular, columnar and equiaxed) and grain size (2.5 μm, 5.0 μm, 7.5 μm and 10.0 μm) of a specified metal and the calculated solidification parameter (G/R, G × R) of temperature gradient (G) and solidification rate (R) is calculated by comparing the “solidification process percentage” of the welding experiment and simulation. Taking pulsed laser single spot welding as the object, the varying solidification parameters and corresponding microstructure of liquid–solid interface are obtained by adjusting the pulsed closing shapes. The results show that the calculating method of the solidification parameter threshold of the welding microstructure evolution by using the solidification process percentage is reliable and the evolution threshold of microstructure morphology and the grain size of AZ31 magnesium alloy are obtained. The research lays a theoretical and practical foundation for the establishment of the solidification parameter threshold system of the welding microstructure evolution.

Influence of heat input on intermetallic formation in dissimilar autogenous laser welding between Inconel 718 and AISI 316L steel

Intermetallic formation during dissimilar welding of Inconel and stainless steel significantly hinders producing sound-quality weld. In the present work, a high-power CO2 laser welding system is employed to join Inconel 718 and AISI 316L stainless steel without using any filler materials. The finite element based thermal model provides the temperature distribution in the weld zone and consequently the solidification parameters (G/R and G.R). The micro-segregation and intermetallic formation in laser welding are correlated with these solidification parameters. The segregation of principal alloying elements triggers the formation of intermetallic phases during solidification. The presence of various phases like Laves, NbC, and TiC in the fusion zone reduces with increase in heat input. The amount of these intermetallic phases present in the weld zone is estimated by XRD analysis. With an increase in heat input, the mode of solidification changes from columnar to equiaxed dendrites that is characterized at reduced value of solidification parameter (G/R). The intermetallic Laves particle diminishes significantly (more than 90%) with a reduction of G/R parameter. In equiaxed dendrites, the segregation and formation of these secondary particles reduces to more than 40% compared to the columnar dendritic structure. Overall, the reduction in the intermetallic particles improves the joint efficiency up to 100% with an elongation of 14.2% for the equiaxed structure of the laser welding system.

Thermo-fluid flow behavior of the IN718 molten pool in the laser directed energy deposition process under magnetic field

PurposeThis paper aims to understand the magnetohydrodynamics (MHD) mechanism in the molten pool under different modes of magnetic field. The comparison focuses on the Lorenz force excitation and its effect on the melt flow and solidification parameters, intending to obtain practical references for the design of magnetic field-assisted laser directed energy deposition (L-DED) equipment.Design/methodology/approachA three-dimensional transient multi-physical model, coupled with MHD and thermodynamic, was established. The dimension and microstructure of the molten pool under a 0T magnetic field was used as a benchmark for accuracy verification. The interaction between the melt flow and the Lorenz force is compared under a static magnetic field in the X-, Y- and Z-directions, and also an oscillating and alternating magnetic field.FindingsThe numerical results indicate that the chaotic fluctuation of melt flow trends to stable under the magnetostatic field, while a periodically oscillating melt flow could be obtained by applying a nonstatic magnetic field. The Y and Z directional applied magnetostatic field shows the effective damping effect, while the two nonstatic magnetic fields discussed in this paper have almost the same effect on melt flow. Since the heat transfer inside the molten pool is dominated by convection, the application of a magnetic field has a limited effect on the temperature gradient and solidification rate at the solidification interface due to the convection mode of melt flow is still Marangoni convection.Originality/valueThis work provided a deeper understanding of the interaction mechanism between the magnetic field and melt flow inside the molten pool, and provided practical references for magnetic field-assisted L-DED equipment design.

Effect of Bi and Ca on the Solidification Parameters of Sr-Modified Al-S-Cu (Mg) Alloys.

The effect of tramp elements, mainly Bi and Ca, on the thermal characteristics of Sr-modified Al–Si–Cu and Al–Si–Cu–Mg alloys has been investigated using thermal analysis, X-ray radiography, and field emission scanning electron microscopy (FESEM) techniques. The high affinity of Bi to interact with Sr results in an increase in the Al-Si eutectic temperature, and hence an increase in the size of eutectic silicon particles. In contrast, the Ca–Sr interaction seems to have no significant effect on the alloy thermal behavior. The effect of these interactions on porosity formation has been discussed. Hot zones may be formed in thin cavities, in particular, near the bottom of the mold, leading to formation of unexpected coarse porosity, mostly shrinkage type. The study also highlights the significance of other parameters on porosity formation, such as no melt degassing, SrO, Al2O3 (strings or bifilms), as well as the presence of iron-based intermetallics.

Research on the evolution mechanism of solidified structure during laser cladding IN718 alloy

• An improved CA-FE model is used to explore the evolution of the microstructure. • A CET model is established to quantitatively study the solidification parameters. • The relationship between solidification parameters and microstructure is explored. • The mechanism of grain growth during the solidification is revealed. • Increasing the laser power and scanning speed will promote the CET process. In the direct energy deposition (DED) process of IN718, the microstructure significantly affects the properties of the workpieces, but the evolution mechanism of the microstructure has not been systematically studied, so it is valuable to understand the solidification process in the molten pool. In this study, a simplified temperature field model is established and the cellular automata (CA) model is used to explore the evolution of the microstructure during DED, which can effectively simulate the microstructures of IN718 with different process parameters. Then a columnar to equiaxed crystal transition (CET) model is established to quantitatively reveal the relationship between solidification parameters and microstructures throughout the solidification process, and the mechanism of grain growth during the solidification of molten pool is further explored, finding that increasing the laser power and scanning speed will promote the CET process with the equiaxed crystal content increasing from 6.18% to 33.8%. This study can be used to simulate the solidification process of IN718 during DED and obtain the required microstructures by optimizing the processing parameters.

Deciphering the individual effects of the fluid flow and material evaporation physics on the melting characteristics and the re-solidification parameters during laser melting of solid Ti6Al4V substrate

• Underlined individual effects of fluid flow and material evaporation separately. • Effect of adding various physics on the computational time consumption presented. • Four different models have been investigated for laser melting of Ti6Al4V. • Optimal numerical model for laser melting has been identified. • Detailed discussion on the solidification parameters in melt pool presented. In this study, the effect of inclusion of fluid flow and material evaporation physics in the thermal models of the laser melting process for Ti6Al4V has been compared to evaluate their individual influence on the simulation results and computational resources consumed. Though the study seems basic, it aims to address the important issue of increase in the computational resources consumption and time when these physics are added to the model. The study also focuses upon finding an optimized model that can enable faster prediction of thermal and melt pool dimension results for macro-scale laser melting cases, while ensuring the accuracy of these results against the experimental observations. It was seen that the fluid flow and material evaporation assisted each other in some aspects and opposed in some others, but the extent of their individual effects varied significantly in the magnitudes. Along with the individual melt pool characteristics comparison, the thermal field along the length, width and depth of the computational domain as well as the computational time consumed by each simulation are also compared for different models. It is obtained through experimental validation that material evaporation could reduce the reliance on the fluid flow inclusion in the model to accurately predict the melt pool dimensions, that too while consuming drastically less computational time. Through these comparisons and experimental validation, an optimized model has been identified, which is then used to present a parametric analysis of the solidification variables (G, R, GR and G/R) for the laser melting of Ti6Al4V.

Offset impacting of a liquid aluminum droplet train on a molten pool on a horizontally moving substrate during TIG-assisted droplet deposition manufacturing

Internal metallurgical defects and poor mechanical properties and surface quality of the formed parts are the most important challenges of metal micro-droplets deposition manufacturing technology. Lack of strong coalescence between neighboring droplets and the blocking effects of periodic ripples on the fusion process are major sources of abovementioned problems. To address this issue, a tungsten inert gas (TIG) welding arc was introduced to pre-melt the material below the droplet impacting location, thus, one droplet train will be deposited on a curved molten pool surface to fabricate deposited layers in an additive approach. In the present work, a numerical model based on the computational fluid dynamics (CFD) method was developed to investigate the dynamic behaviors of successive droplets’ impact and coalescence on the molten pool created by a tilted TIG welding arc, and focuses on the effect of the offset distance between the impacting point of droplet and the longitudinal plane of molten pool on the deposition morphology and the impact-induced molten pool behaviors. The simulated tracks exhibit regular scaly shapes at different offset distances, which is validated against the corresponding experiments. The results indicated that as the lateral offset distance increases, the symmetric spreading and recoiling of the subsequent droplets on the pre-existing bead will be broken due to the inclined and curved solidification front morphologies, the inclined front morphologies are caused by the increased growth rate of the solidification front at the impact zone. With an increased lateral offset distance, the volume of the molten pool decreases, the width of the rear molten pool increases slightly. The calculated solidification parameters are found to be dependent of the offset distance, and vary significantly at the onset of solidification at different portions of the molten pool. The scientific findings provide useful insights for further researches of TIG-assisted DDM.

Development of a Novel Welding Technique With Reduced Heat-Input by Employing Double-Pulsed Gas Metal Arc Welding for Aerospace Grade 18% Ni Maraging Steel

Abstract Eighteen percent Ni maraging steels are high performance Fe–Ni martensite-based alloys with ultra-high strength and good toughness. They find applications in strategic sectors, joining of thick sections often coming into picture. Welding of thick section involves a longer processing time, more passes, and a higher heat-input. Double-pulsed gas metal arc welding (DP-GMAW) is an emerging welding technique, well suited for joining thick sections. DP-GMAW is capable of controlling the solidification parameters, weld pool geometry, and cooling rate at a reduced heat-input. The major concern regarding the welding of maraging steel is the formation of the reverted austenite (RA) phase in the fusion zone (FZ). The formation of RA deteriorates the mechanical performance of welded joints. The presence of RA can be supressed by the usage of suitable welding techniques and proper post-weld heat treatments (PWHTs). DP-GMAW process was employed to carry out the welding; studies on the joints produced are reported in this research paper. The studies also included the effect of various PWHTs on the metallurgical and mechanical properties of the maraging steel weldments. The research used three distinct PWHTs: direct aging (DA), solutionizing + aging (SA), and homogenizing + solutionizing + aging (HSA). The FZ microstructures under DA and SA conditions show that there is RA at the cell boundaries. However, there was no evidence of RA in FZ following HSA. The energy dispersive spectra (EDS) analysis of the as-welded FZ showed segregation along the grain boundaries (GBs). This led to the premature formation of RA upon subsequent aging. The SA treatments proved inadequate to totally eliminate RA in the microstructure. On the other hand, the HSA treatments were effective in evening out concentration differences and preventing formation of RA. This study demonstrates that DP-GMAW combined with HSA treatment has the best mechanical properties.

Experimental and numerical study on the effect of increasing frequency on the morphology and microstructure of aluminum alloy in laser wobbling welding

Laser wobbling welding is effective in reducing porosity and improving microstructure of aluminum welds. This work adopts the research form of experiment combined with numerical simulation to establish the relationship between different parameters and morphology and microstructure of the welds. The dynamic behavior of the molten pool and the keyhole, the thermal cycle process and the solidification parameters can be obtained through the numerical simulation considering the fluid flow and heat transfer. The research reveals that laser wobbling welding improves the weld formation by significantly weakening the molten pool eruption and stabilizing the welding process and also confirms that there is a special cross-regional flow field in the molten pool and the mushy zone which is different from ordinary laser welding. In addition, it is proved that the grain refinement at the weld boundary is the result of the combined effects of solidification parameters, dendrite remelting and flow field stirring, but the grain refinement at the center of the weld is mainly caused by the flow field stirring. These results explain the influence of the laser wobbling welding on the flow, heat transfer and solidification parameters of the welds and reveal the reasons for improving the weld formation and refining the microstructure.

Microstructure evolution, mechanical properties of FeCrNiMnAl high entropy alloy coatings fabricated by laser cladding

In this work, FeCrNiMnAl high entropy alloy (HEA) coatings under different laser energy density (Led, 50–92 J/mm2) were fabricated on 17-4PH stainless steel by laser cladding (LC). The influence of different laser energy density on the geometric morphology, microstructure, microhardness and tribological properties of HEA coating was investigated. To obtain the specific solidification parameters (temperature gradient and solidification rate), the finite element model was established to express the transient change of molten pool temperature field. The columnar-to-equiaxed transition (CET) corresponding to different zones of HEA coating was revealed. The result showed that the geometric parameters increased with the rise of Led because of the Marangoni convection. Equiaxed crystals and columnar crystals were distributed on the top and bottom zones of HEA coatings respectively, and the CET behavior was observed. Higher temperature gradient and lower solidification rate were conducive to the growth of columnar-crystals. Furthermore, at the Led of 92 J/mm2, HEA coatings showed relatively high crack sensitivity. HEA coatings significantly improved the tribological properties owing to metal oxide particles generated by oxidation. In the mechanical properties test, the maximum microhardness of prepared HEA coating (1800 W) was 587.83 HV0.2, which was 1.63 times that of 17–4PH substrate. Metal oxide particles generated a flat wear-resistant enamel layer which protected the coating surface. The tribological properties was optimal at the Led of 64 J/mm2, the average friction coefficient and wear rate were 0.4654 and 7.026 × 10−8 mm2/N, respectively.

Microstructure Analysis of Al-7 wt% Si Alloy Solidified on Earth Compared to Similar Experiments in Microgravity

During ground-based solidification, buoyancy flow can develop by the density difference in the hypoeutectic type of the alloys, such as Al-7 wt% Si alloy. Buoyancy flow can affect the thermal field, solute distribution in the melt, and the position and amount of the new grains. As solidification is a very complex process, it is not very easy to separate the different effects. Under microgravity conditions, natural convection does not exist or is strongly damped due to the absence of the buoyancy force. Therefore, experiments in microgravity conditions provide unique benchmark data for pure diffusive solidification conditions. Compared to the results of the ground-based and microgravity experiments, it is possible to get information on the effect of gravity (buoyancy force). In the framework of the CETSOL project, four microgravity solidification experiments were performed on grain refined (GF) and non-grain refined Al-7 wt% Si alloy onboard the International Space Station in the Materials Science Laboratory. These experiments aimed to study the effect of the solidification parameters (solid/liquid front velocity vSL, temperature gradient GSL) on the grain structure and dendritic microstructures. The microgravity environment eliminates the melt flow, which develops on Earth due to gravity. Four ground-based (GB) experiments were performed under Earth-like conditions with the same (similar) solidification parameters in a vertical Bridgman-type furnace having four heating zones. The detailed analysis of the grain structure, amount of eutectic, and secondary dendrite arm spacing (SDAS) for different process conditions is reported and compared with the results of the microgravity experiments. GB experiments showed that the microstructure was columnar in the samples that do not contain GF material or in case the solid/liquid (vSL front velocity was slow (0.02 mm/s)). In contrast, in the sample which contained GF material, progressive columnar/equiaxed transition (PCET) was observed at vSL = 0.077 mm/s and GSL = 3.9 K/mm. The secondary (SDAS) dendrite arm spacing follows the well-known power law, SDAS=K[t0]13, where K is a constant, and t0 is the local solidification time for both GB and µg experiments.

Establishing reduced-order process-structure linkages from phase field simulations of dendritic grain growth during solidification

Establishing a rigorous quantitative relationship between solidification parameters and microstructure is critical for facilitating the fabrication of metallic components with desired properties. Conventional approaches are time and effort intensive and lack a rigorous framework for the systematic and accurate quantification of microstructure. In this study, a novel data science approach is applied to extract high-value, computationally low-cost process-structure linkages from phase field simulations of dendritic grain growth during solidification. Reduced-order measures, which are adequate for identifying the salient features of microstructures and evaluating the effects of solidification process parameters, are obtained through two-point statistics and principal component analysis. Building on these reduced-order measures, computationally efficient surrogate models are established using various regression methods. It is demonstrated that the surrogate model with the best predictive performance can provide good predictions of not only the reduced-order measures but also the two-point statistics. Moreover, it is found that some reduced-order measures exhibit very complex relations with process parameters, which results in poor prediction accuracy. Compared with discarding the features with inaccurately predicted values, including them may lead to worse recovery of higher-order microstructure statistics. These results highlight the importance of microstructure feature selection in the improvement of prediction accuracy.

Scan strategies in EBM-printed IN718 and the physics of bulk 3D microstructure development

Three-dimensional (3D) characterization provides opportunities for understanding processing-structure relationships in additively manufactured (AM) materials. Bulk samples of Inconel 718 were fabricated via electron beam melting (EBM) in order to study microstructural development as a function of energy input and beam scan strategy. TriBeam tomography of bulk Inconel 718 microstructures built under steady-state growth conditions reveals the sensitivity of microstructure formation and evolution to machine process parameters. In this study, samples manufactured using a narrow range of energy input per unit build area result in varied grain morphologies and crystallographic textures. Using TRUCHAS, a thermal simulation software, the thermal history of bulk scan strategies was predicted, and combined with a calibrated microstructure-processing map to accurately predict bulk grain morphologies. The solidification parameters and the 3D measured nucleation density are used to predict the transition between columnar and equiaxed grain morphologies, providing a process map to guide AM parameter choices to locally control as-printed microstructure. A two-dimensional metric for characterizing bulk grain morphology was also found to agree well with predictions from the process map calibrated by 3D data. Combined with 3D tomography and thermal modelling, the physics of structure development were understood at a new level of detail with respect to the competing processes of grain nucleation and epitaxial growth.