Dendritic Spacing Research Articles

Effects of Y addition on carbide morphology and impact properties of D2 cold work die steel

In this study, heavy rare-earth Y element was added to D2 cold work die steel to improve its carbide morphology and distribution, thereby increasing its impact resistance. A comprehensive study was conducted on the morphology and distribution of carbides in D2 steel in the as-cast, as-forged, and spheroidized annealing states. After the forging process, the degree of breakage of the network distribution of the as-forged M7C3 eutectic carbide morphology in the Y-containing D2 steel increased. As the Y content increased from 0 to 0.0210 wt%, the secondary dendrite spacing of the as-cast M7C3 eutectic carbides as well as the volume fraction and average size of carbide clusters decreased from 43 μm, 16.7%, and 29 μm–31.96 μm, 14.2%, and 23 μm, respectively. After the spheroidized annealing process, the addition of Y increased the M7C3 eutectic carbide spheroidization degree. Moreover, the number of the M7C3 secondary carbides increased from 50/25 to 71/25 μm2, and Y addition increased the number of dimples in the impact fracture and proportion of high-angle grain boundaries from 79.1% to 93.4%. Finally, the longitudinal impact toughness of D2 cold work die steel increased from 103.9 to 163.2 J.

Study on the Effect of Al-10Sr Intermediate Alloy on the Modification of A356 Aluminum Alloy after Different Purification Treatments

Abstract For three different purification treatment methods of aluminum melt: untreated (UT), conventional purification treatment (CPT), impurity removal flux purification treatment (IRF), and Al-10Sr intermediate alloy was applied for modification treatment. The results showed that due to the highest purity of aluminum liquid treated with IRF, the secondary dendrite spacing decreased by 31.32% after modification, and the eutectic silicon phase was in a granular and dispersed distribution. The tensile fracture exhibited ductile fracture characteristics, effectively improving the mechanical properties of the alloy. At the same time, it was found that reducing the Sr content did not decrease the modifying effect, indicating good purity of aluminum liquid can provide superior melt conditions for subsequent modification treatment.

Machine learning-assisted wire arc additive manufacturing and heat input effect on mechanical and corrosion behaviour of 316 L stainless steels

Predicting the track forming factor or height-to-width ratio (H/W) in wire arc additive manufacturing is crucial for optimal path planning, heat distribution, structural integrity, distortion control, process efficiency, and defect prevention, ensuring high-quality and reliable components. Different analytical and numerical modeling methods have been introduced to predict the H/W ratio. However, the accuracy of these predictions is relatively low due to the challenges associated with handling complex and non-linear regression equations. This study addressed the challenges by implementing data-driven predictive modeling to predict the H/W ratio from the input process parameters. A stacking ensemble learning approach is employed, where a meta-model integrates predictions from multiple base learners to enhance overall performance. The model performance was evaluated by Coefficient of determination (R2), mean squared error (MSE), and mean absolute error (MAE). The model was validated by comparing the experimental and predicted values based on which five thin walls are printed with different heat inputs. The study also explores the impact of heat input on microstructure, mechanical, and corrosion properties. The findings indicate that a significantly low heat input (178 J/mm) and higher heat inputs (> 356 J/mm) decrease the wire utilization. With increasing heat input, ferrite content increases, microstructures become coarser, dendritic spacing increases, and ferrite transitions from lathy to skeletal. Further, lower heat input (235 J/mm) reduces δ-ferrite, suppresses atomic segregation, and increases Cr and Mo in the matrix. YS and UTS decrease with higher heat inputs, anisotropy decreases, and Vickers microhardness drops from 228 (178 J/mm) to 194 Hv (586 J/mm). Additionally, the corrosion resistance deteriorates with increasing heat input, as evidenced by higher pitting potential (Epit: 0.389 V vs. 0.368 V vs. −0.023 V) and lower corrosion current density (Icorr: 6.76 ×10−7 A/cm2 vs. 7.946 ×10−7 A/cm2 vs. 8.91 ×10−7 A/cm2) for heat inputs of 235 J/mm, 281 J/mm, and 356 J/mm, respectively.

Mechanism of grain boundary angle on solidification cracking in directed energy deposition Hastelloy X superalloys

Solidification cracking occurs only when the grain boundary (GB) angle (θ) exceeds a critical value. This value, known as the critical cracked GB angle (θ*), can be predicted from the grain coalescence theory based on GB-angle-dependent GB energy. However, the calculated value (θc*) is always less than the measured value in experiments (θe*), which is also confirmed in our directed energy deposition Hastelloy X superalloys. In addition to GB energy, there are evidences showing that GB angle can affect cracking by changing dendrite spacings. We show by experiments and phase field simulations that, same as GB energy, the dendrite spacings at GBs increase with GB angle, but its effect on solidification cracking sensitivity (SCS) is opposite to GB energy. Depending on their relative contributions, three ranges can be identified. In the first range of θ<θc*, both dendrite spacings and GB energy have negligible effects on dendrite coalescence, compared to the case inside a grain. In the second range of θc*<θ<θe*, dendrite spacings counteract the effect of high GB energy on SCS. It is exactly this effect that induces the gap in θ* between theory and experiments. In the third range of θ>θe*, GB energy plays a dominant role and leads to severe solidification cracking. After including the effect of dendrite spacings on SCS, we predict θ*=15° in directed energy deposition Hastelloy X superalloys, close to the experimental value of 18°. These new findings provide new insights for suppressing cracking by controlling the dendrite spacings near GBs.

Towards optimizing cooling rate, microstructure, and compressive strength in rapidly solidified Cu–20Fe alloy

There is currently interest in the development new Cu–Fe alloys with higher Fe content (>5 wt%), a low-cost element. In order to improve electrical, thermal and mechanical properties, there is a need to decrease the size of the Fe-rich phase and improve its distribution, whose possibilities rely on adding alloying third elements and heat treatments. However, the prospect of controlling the size of the phase through dendritic spacing control by means of rapid solidification processes may be feasible and deserves to be explored, as is the case in the present study. The following methods were employed to evaluate the round stepped cast samples of the Cu-20 wt% Fe alloy: centrifugal casting in a Cu mold, optical microscopy, CALPHAD, Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS), X-ray Diffraction (XRD), Vickers hardness, and compressive tests, in samples corresponding to different coarsening microstructures. Finally, dendritic growth is modelled using the Kirkwood equation. The results demonstrate a promising processing route with control of the secondary dendrite arm spacing (SDAS), whose methodology and modeling can serve as a basis for other alternative processes with the Cu–Fe alloys, allowing suitable size and distribution of Fe phase to be attained. It is further demonstrated that the Kirkwood model is able to match experimental SDAS in both slowly and rapidly solidified Cu–Fe samples. While Fe (BCC) is expected to increase strength, this is only slightly observed in the hardness results for smaller SDAS, as the loads are more superficial. In the case of compressive yield strength, SDAS in the observed range (1.4 μm–2.2 μm) is found to have no effect.

Effect of Boron on the Solidification Characteristics and Constitutive Equation of S31254 Superaustenitic Stainless Steel

Solidification structure and segregation behavior of S31254 superaustenitic stainless steel ingot containing 0 wt% B and 0.005 wt% B are investigated. The results show that serious element segregation and massive eutectics are present in the center of the ingot. By contrast, the addition of boron reduces the secondary dendrite spacing, the degree of elemental segregation, and the σ phase. Further, the effect of boron on the solidification process is studied by using the high‐temperature confocal laser scanning microscope and combined with Thermo‐Calc thermodynamic simulation results. The results show that boron can widen the solidification temperature range and greatly retard the matrix solidification. The role of boron in refining dendrite structure and inhibiting precipitation is further confirmed. The effect of boron on the constitutive equation of S31254 superaustenitic stainless steel has also been researched through isothermal compression testing in the temperature range of 950–1200 °C and strain rate range of 0.01–10 s−1. The activation energy of the boron‐free and boron‐containing S31254 superaustenitic stainless steels based on the constitutive equation are 427.77 and 495.80 kJ mol−1, respectively. Processing maps indicate that the instability domain is significantly reduced and the hot ductility is improved after the addition of B.

Bridging molecular dynamics and additive manufacturing: A study of Al-12 at% Si alloy solidification dynamics

This manuscript provides a detailed analysis of the molecular dynamics of the directional solidification process in Aluminum-Silicon (Al-12 % at Si) alloys, with a particular emphasis on applications in additive manufacturing. Utilizing molecular dynamics (MD) simulations, the study examines large systems containing 5–15 million atoms to investigate various facets of the solidification process. These include the dynamics of interface motion and the formation of Silicon (Si) precipitates. The research reveals significant variations in interface velocities and orientations across different thermal gradients and growth rates, underscoring the intricate interaction between thermal and solute flows in the microstructural development of Al-Si alloys. These findings are vital for comprehending and refining the solidification process in additive manufacturing, ultimately enhancing the mechanical strength and reliability of the final products. The paper highlights the critical role of microstructure control in printed metals and proposes future research directions, aiming to apply these insights to more complex alloy compositions and manufacturing contexts. In the concluding phase, the scikit-image library was employed to analyze dendritic formations in solidifying Al-Si alloys using MD simulations. This analysis delineates trends in dendritic count, spacing, perimeter, and area over time, offering essential perspectives on the solidification process and its implications for the alloy's microstructure and mechanical characteristics. The Si content in the Al-Si alloy used can be considered eutectic in the solidified structure. Si atoms are predominantly located at grain boundaries and precipitate regions. Coordination number analysis further confirms the presence of Si in these locations. This microstructure, characterized by a primary Al/Al-Si matrix and Si-rich eutectic regions, aligns with experimental observations in rapid solidification processes in additive manufacturing.

Introducing high-density growth twins in aluminum alloys by laser surface remelting via templated nucleation of grains

It is difficult to generate coherent twin boundaries in bulk Al alloys due to their high intrinsic stacking fault energy. Here, we report a strategy to induce high-density growth twins in aluminum alloys through the heterogeneous nucleation of twinned Al grains on twin-structured TiC nucleants and the preferred growth of twinned dendrites by laser surface remelting of bulk metals. The solidification structure at the surface shows a mixture of lamellar twinned dendrites with ultra-fine twin boundary spacing (∼2 μm), isolated twinned dendrites, and regular dendrites. EBSD analysis and finite element method (FEM) simulations have been used to understand the competitive growth between twinned and regular dendrites, and the solidification conditions for the preferred growth of twinned dendrites during laser remelting and subsequent rapid solidification are established. It is shown that the reduction in the ratio of temperature gradient G to solidification rate V promotes the formation of lamellar twinned dendrites. The primary trunk spacing of lamellar twinned dendrites is refined by the high thermal gradient and solidification rate. The present work paves a new way to generate high-density growth twins in additive-manufactured Al alloys.

Role of layer arrangement in microstructure and corrosion behavior for 78-mm thick-plate 316L stainless steel fabricated via narrow gap laser wire filling welding

Controlling repeated thermal cycling is one of the key mechanisms to design microstructures in the interlayer regions for narrow gap laser wire filling welding (NGLWFW) of austenite stainless steels. Herein, the optimization of process parameters for individual layers is tailored to customize the molten pool morphology during the NGLWFW process, facilitating precise control over the microstructure and, consequently, enhancing both mechanical properties and corrosion resistance of the joint. The results showed that the molten pool morphology acquired by simulation are obviously diverse from the bottom zone (BZ), middle zone (MZ) to upper zone (UZ) of the welded joint ascribed to the high heat accumulation effect, leading to the variation of microstructure. At BZ, the combination of smaller grain size and reduced dendrite spacing reduce the number of corrosion sites and promote the formation of a denser and more uniform corrosion product layer. Additionally, the diverse grain orientation, characterized by lower texture strength, facilitated a more uniform distribution of elements. Furthermore, the significantly higher content of δ-ferrite showing smallish shape disrupted the directional growth of austenite columnar grains, contributing to the excellent corrosion resistance observed at the BZ.

Effect of Ce and solidification cooling rate on the microstructure and mechanical properties of AA2017 aluminum alloy

Controlling dendritic growth and grain size in new Ce-containing Al-based alloys becomes crucial due to new envisioned applications and Ce rising demand in casting processes. In the present work Ce effect on the 2xxx Al series microstructures at various industrial-scale solidification cooling rates was investigated. The directional solidification technique is crucial in this endeavor since can generate several solidified samples related to several cooling rates. The AA2017 alloy and a modified version containing 3 wt % of Ce were both produced under directional solidification and various microstructure aspects were characterized. The mechanical behavior was analyzed by microhardness and compression tests. The Ce addition reduced primary and secondary dendritic spacing without impacting grain size. Cells were only observed to form on the Ce-containing alloy at cooling rates of approximately 19 °C/s; while dendritic configurations dominated all other conditions. While round pockets composed of Al+Al2Cu+Mg2Si ternary eutectic formed the interdendritic zones in the AA2017 alloy, the AA2017-Ce alloy microstructure was mainly constituted by elongated AlCeSi + Al8CeCu4 interdendritic phases. Finally, the addition of Ce favored an increase in the microhardness and compressive strength values of the AA2017 alloy, which is attributed to the refinement of the solidification structure, as well as the formation of a greater fraction of secondary reinforcement phases.

Effect of welding current and speed on solidification cracking susceptibility in gas tungsten arc fillet welding of dissimilar aluminum alloys: Coupling a weld simulation and a cracking criterion

In order to study the effect of welding current and speed on the solidification cracking susceptibility of weld, gas tungsten arc welding of a fillet weld with a cold filler wire was simulated. Simulation was conducted for dissimilar welding of Al–Cu–Mg to Al–Mg–Si aluminum alloys with an Al–Mg filler metal at the welding current range of 145–175 A and welding speed of 18–24 cm/min. The outcomes of simulations, namely temperature gradient, velocity of isotherms, and weld chemical composition obtained for various welding currents and speeds, were used as inputs for a solidification cracking model. The results showed that the dimensions of the weld profile obtained from the simulation exhibited good agreement with experimental results. However, a discrepancy of 10–23% was observed between experimental and simulated results in relation to one dimension of the weld profile, i.e. the distance between the fillet weld corners. This discrepancy was addressed to identify the underlying reasons. According to the model proposed in this study for solidification cracking of aluminum alloys, both higher welding current and higher welding speed led to a higher susceptibility to solidification cracking. This result was justified by considering factors such as secondary arm spacing of dendrites, isotherm velocity, backfill time, and chemical composition and viscosity of the weld pool. Weldability tests were employed to validate the model's performance for predicting the solidification cracking susceptibility. Thus, the optimal welding parameters can be chosen in accordance with these results and production demands.

Microstructure evolution and property of high manganese steel coatings by laser shock assisted laser wire cladding

Field-assisted laser cladding (FALC) overcomes the limitations of laser cladding through the inherent advantages brought about by the use of various auxiliary energy fields (AEFs). Laser wire cladding (LWC) is limited by the common problems of laser cladding but has a promising future due to the extremely high material utilization rate. In this study, a laser shock assisted laser wire cladding (LSALWC) manufacturing process was proposed. In situ laser shock was introduced into the LWC to obtain finer grains structure and improve product performance. LSALWC does not change the composition of the coating, does not require the use of pretreatment and post-treatment, and does not reduce the efficiency of production. Using high manganese steel (HMS) as the model alloy, LSALWC was employed to achieve the expectation of reducing the proportion of columnar grains, refine the microstructure of columnar grains, and transform columnar grains into equiaxed grains. Compared with the sample (LC) manufactured by LWC, the performance of the sample (LSA) manufactured by LSALWC has been improved, the hardness increased from 285 ± 5 HV0.5 to 303 ± 6 HV0.5, the volume wear rate decreased from 2.1 × 10−4 mm3/N·m to 1.7 × 10−4 mm3/N·m, the primary dendrite spacing of the coating was reduced by 11.5%, and the heterogeneity of coating was more obvious. The cladding process under laser shock was studied using a high-speed camera, and the influence of laser shock on the coating was explained. The mechanism of the performance improvement of the LSA sample was explained. This study showed the disturbance of the molten pool was enhanced by laser shock, and the dendrites at the bottom were deflected or even broken. The broken dendrites were dispersed with the liquid flow and became new nucleation sites. Laser shock increased the supercooling during solidification by reducing the temperature gradient in the molten pool, and created an environment conducive to grain nucleation and growth. This process mitigates various issues in the casting process of HMS and provides a novel method for regulating the grain and microstructure of laser cladding. This research delves into the coupling between the AEF and the dynamic behavior of the molten pool, culminating in a model depicting the evolution of laser cladding solidification under the influence of the AEF, which will provide a new perspective for the research of FALC.

Effect of Ce Addition on Inclusions and Primary Carbide Network in AISI 440C Bearing Steel

The effects of Ce on inclusions and the primary carbide network of AISI 440C bearing steel are experimentally and theoretically investigated. Adding Ce improves the cleanliness and refinement of primary carbide networks in AISI 440C bearing steel ingots. The addition of Ce substantially reduces the contents of total oxygen (T.O) and S in the steel, and MnS and Al2O3 inclusions are modified into finer Ce‐containing inclusions (Ce2O2S and Ce2O3). When Ce is added, the average equivalent diameter of the inclusions decreases from 1.82 to 1.33 μm, and the number of inclusions per unit area (mm2) increases from 59 to 105. Moreover, the addition of Ce reduces the secondary dendrite spacing from 33.82 to 24.2 μm, and the proportion of primary carbide is reduced from 22.08% to 11.17%. The 2D lattice disregistry theory confirms that Ce2O2S and Ce2O3 inclusions can be utilized as effective heterogeneous nucleation cores for γ‐Fe, thus refining the solidification microstructure and also the primary carbide. This study provides theoretical guidelines for the fabrication of domestic AISI 440C bearing steel ingots.

Effect of secondary orientation on the microstructures in thin-walled castings of nickel-based single-crystal superalloys

With the increasing turbine inlet temperature of aero-engine, the requirement of temperature capacity of turbine blades is more stringent. A variety of complex cooling structures have been designed, among which the micro cooling represented by lamilloy is the latest development. At present, the thickness of lamilloy turbine blade is 0.5 mm or less. The reason for performance degradation caused by thin-walled is still controversial and the understanding of dendrite growth behaviour under space constraints is insufficient. In this study, 0.75 mm wall thickness nickel-based superalloy DD403 samples were cast by high-rate directional solidification. The growth and evolution of dendrites in plank-shaped specimens with different secondary deviation angles were investigated. The variation of dendrite spacing and the arrangement of dendrites under different secondary deviation angles were studied. It is found that the primary dendrite arm spacing in the thin-walled region decreased with the increase of the secondary deviation angle, but there was no significant change in the average size of γ′ phases and elements segregation.

The Mechanical and Functional Behaviors of Mn–15 wt%Cu Alloy Produced by Selective Laser Melting

Mn–Cu‐based alloys possess excellent mechanical and functional properties (damping capacity and shape memory effect). This work utilizes a typical additive manufacturing technique, selective laser melting (SLM), to fabricate Mn–15 wt%Cu alloys to explore the mechanical and functional behaviors. The results indicate that the γ‐(Mn, Cu) and a small amount of γ′‐(Mn, Cu) phase are the main phase compositions in the as‐SLMed Mn–15 wt%Cu alloy, as well as twins and second‐phase precipitation particles. The microstructure shows a fine cellular γ‐(Mn, Cu) dendrite with primary dendrite spacing of ≈0.9 μm in the columnar grains with a size of ≈8 μm. The martensitic transformation start temperature (MS) and phase transformation hysteresis are ≈132.6 and ≈5.1 °C, respectively. The existing nanoscale chemical segregations of Mn and Cu are attributed to the spinodal decomposition of γ‐(Mn, Cu). A compositional modulation is observed with a wavelength of ≈20 nm and an amplitude fluctuation of Mn (55–85 wt%) and Cu concentrations (15–45 wt%). Finally, the as‐SLMed Mn–15 wt%Cu alloy boasts good tensile properties (359, 268 MPa, and 3.6%), damping (internal friction of 0.032 when the strain amplitude is 9 × 10−4), and shape memory performances (one‐way ηow = 37–48%, and two‐way ηtw = 16–20% under the pre‐deformation strain of 2–3%).

Melt pool evolution and microstructure simulation of SLM 316L based on SPH-PFM coupling model

The study in this work fully utilized the computational advantages of various numerical methods and established a SPH-PFM coupling model for the 316 L SLM process. The temperature field, melt pool changes, and microstructure evolution of the 316 L SLM process were simulated and calculated. The correctness of the simulation results was verified through the comparison with experiments, and a calculation platform for melt pool evolution and microstructure simulation of metal material SLM process with independent intellectual property rights was developed. (1) Establish the mathematical model required for the dynamic simulation of the molten pool in the metal material SLM process based on the SPH method. (2) Extract the temperature field data and molten pool shape from the calculation results based on the SPH method, and then substitute them into the phase field model for molten pool modeling. The formation mechanism of the microstructure morphology inside the molten pool and the micro-segregation mechanism of solute elements at different positions during solidification were analyzed and discussed. The article compared the simulation results with the experimental results. The simulation results showed good consistency with the experimental results in terms of primary dendrite spacing, secondary dendrite spacing, and melt pool microstructure morphology, proving the correctness of the model established in this article. At the same time, the SPH-PFM coupling model established in this article can effectively solve the problem of predicting the microstructure of the melt pool in the SLM process, providing a new method for the study of microstructure prediction in the SLM process.

Technical research on recycling waste blades of single crystal superalloy through ultrasonic alkali cleaning combined with electron beam smelting

The waste blades of single crystal superalloys have not been formally applied on a large scale, resulting in serious waste. This study proposes to treat the waste blades through ultrasonic alkali cleaning combined with electron beam smelting (EBS). The theoretical model is proposed to study the elements volatilization, which provides a reference for controlling the alloy composition. After EBS, the secondary dendrite spacing and the size of γ′ phases of DD5 alloy is significantly reduced. The EBS technology can effectively reduce the element segregation in superalloys, especially W and Mo elements. The purity of DD5 revert alloy after EBS is consistent with or even exceeds that of DD5 virgin alloy. Especially for the removal of ceramic shell and core materials in the waste blades, EBS has a new technological advantage. Under the combined action of Marangoni effect and buoyancy, the inclusions floating to the melt surface can not only be directly decomposed by the bombardment of the electron beam, but also can be dissolved under the condition of local melt superheating.

Casting of film-cooling holes for single-crystal blades

The flawless formation of film-cooling holes (FCHs) is critical for manufacturing single-crystal blade. Presently, high-energy beam drilling is mostly used to process gas film holes, which introduces the limitations of complex hole structures that are difficult to form and processing thermal defects that are difficult to eliminate. This study demonstrates an approach to form FCHs using casting, where an indirect additive manufacturing technology using a core/shell integral ceramic mold is applied for casting. Cylindrical 0.4, 0.8, and 4.0 mm-diameters hole are cast. The influence of fine ceramic cores on the microstructure of single-crystal blades during directional solidification is investigated using simulations and experiments. The fine ceramic cores of the FCHs affect the growth morphology of dendrites around the hole, which is determined by the hole diameter, primary dendrite spacing, and local temperature filed. Owing to the thermal conductivity difference between the alloy and ceramic, the local temperature filed around the holes changes abruptly, leading to the formation of shrinkage porosity and cavities. Furthermore, the process window for the casting of FCHs is determined using the longitudinal temperature gradient (GZ) and solidification rate (VZ). The proposed approach is of practical significance for the defect-free casting of tiny structures in single-crystal blades.

Process Optimization Method for Inhibiting TCP Precipitation in A Nickel-Based Single Crystal Superalloy with High Refractory Element Content

In order to study the optimization method of microstructure stability of high generation single crystal superalloys, the influence of manufacturing process on the microstructure stability of a single crystal superalloy containing high content of refractory elements was studied, and the corresponding process optimization method was obtained. The microstructure characteristics of the alloy at different stages were observed and the corresponding element distribution were tested. The microstructure and element distribution of the alloy at different stages of preparation were analyzed with the assistance of kinetic calculation. Results show that the element dendrite segregation is an important reason to reduce microstructural stability. Reducing the dendrite spacing in directional solidification and increasing element diffusion in solid solution heat treatment can reduce the segregation of refractory elements in the dendrite core. As a result, less TCP precipitates in the dendrite core, and thus improve microstructure stability. Based on analyzed results, the manufacturing process were optimized and proved to be effective.

Solidification, α-Al morphologies, and tensile properties of low-Sc modified Al-Mg alloys

Al alloys are very attractive in engineering applications that require a combination of low density and mechanical strength, such as in aeronautical and aerospace industry devices. Therefore, the search for alloys with higher specific strength is justified from environmental and economic points of view. This work aims to study the influence of cooling rates on the phase morphology and tensile properties of ternary Al-Mg-Sc alloys, whose composition covers the spectrum of low-Sc Al-Mg-Sc alloys. The ternary Al-3, −5, and − 10 wt% Mg-0.1 wt% Sc alloys were processed by transient directional solidification. This process induces a wide range of cooling rates which causes the formation of a microstructural variety along the longitudinal cooling direction and, consequently, different tensile properties. Several characterization methods were employed, including: thermal analysis, x-ray diffraction (XRD) structural analysis, SEM-EDS, optical microscopy, CALPHAD, tensile tests, and fractography. Two major findings should be noted after fully characterizing the microstructures, the formed phases, and the tensile properties. Solidification evolution revealed that more Mg added resulted in higher solidification rates due to higher fluidity with more Mg. Furthermore, cell growth was mapped in the three alloy compositions while competing with dendrites. Solidification scaling relationships between dendritic or cellular spacing and cooling rate for all alloys were examined. Although the Al-10 wt% Mg-Sc alloy had more Mg in solid solution, the Al-5 wt% Mg-Sc alloy showed superior tensile strength due to the predominance of cells and thinner primary dendrites trunks forming its microstructure.