arXiv subjects

S. Mohadeseh Taheri-Mousavi

Publications and source records attributed to S. Mohadeseh Taheri-Mousavi.

4 recordsLinked to original sources

arXiv2026

Computational Design of Ductile Additively Manufactured Tungsten-Based Refractory Alloys

Tungsten exhibits exceptional temperature and radiation resistance, making it well-suited for applications in extreme environments such as nuclear fusion reactors. Additive manufacturing offers geometrical design freedom and rapid prototyping capabilities for these applications, provided the intrinsic brittleness and low printability of tungsten can be overcome. Designing tungsten alloys with improved ductility, and thus printability in additive manufacturing, can be accelerated using a computationally derived performance predictor to screen out brittle compositions. Calculations of the Pugh ratio using density functional theory may serve this purpose, given its correlation with ductility. This process can be made more efficient through the use of machine learning interatomic potentials to accelerate density functional theory calculations. Here, we demonstrate that machine learning interatomic potentials can effectively identify optimal alloy compositions in the W-Ta-Nb system along the melting point-Pugh ratio Pareto front. The trend in Pugh ratio as a function of tungsten fraction is explained in terms of the electronic density of states at the Fermi level. Experimental validation reveals a strong correlation between the computed Pugh ratio and the observed crack fractions in additively manufactured alloys. Notably, the two alloys predicted to have the highest Pugh ratio values, W20Ta70Nb10 and W30Ta60Nb10, exhibit no intergranular microcracking in experiments.

cond-mat.mtrl-sci↗

arXiv2025

Computational statistics of segregation and dislocation activities of hydrogen charged free surfaces and grain boundaries

Revealing statistics of H-defect interactions provides insights into significant ductility loss due to the particular strain partitioning in H-charged structural alloys. Experimental investigation of these interactions is extremely difficult, labor-intensive, and costly. Here, we used MD and GCMC simulations and studied H-diffusion deformation at polycrystalline scale with atomic resolution efficiently. To study H-free surface interactions, large pillars including all possible angles and planes of free surfaces were modeled. To study H-grain boundary interactions, several polycrystalline models containing comparable statistics of low and high angle grain boundaries were examined. We studied the statistics of H-segregation tendencies based on free surface angles and grain boundary types. Dislocation activities were also classified for these various types and total density and strength were compared and analyzed compared to H-free samples. In the free surface model, it was observed that H was evenly distributed along the model's surface. Although the dislocation density was reduced compared to H-free samples, localized bands of dislocations were produced. Additionally in the polycrystalline samples, it was concluded that H tends to segregate along grain boundaries with misorientation angles less than or equal to 25 degrees. However, specific misorientation angle interactions -- namely $>45$ degrees -- led to increased dislocation density in H-charged samples compared to their H-free counterparts.

cond-mat.mtrl-sci↗

arXiv2025

Additively manufacturable high-strength aluminum alloys with thermally stable microstructures enabled by hybrid machine learning-based design

Additively manufactured (AM) aluminum alloys with high strength and thermal stability have broad applications in turbine engines, vacuum pumps, heat exchangers, and many other industrial systems. Employing precipitates with an L1$_2$ structure to block dislocation motions is a widespread strategy to strengthen aluminum. However, to achieve high strength, a high volume fraction of small precipitates is required, and these characteristics are generally mutually exclusive. Here, we show that for certain compositions of Al alloys, L1$_2$ phases initially precipitate as sub-micron metastable ternary phases under the rapid solidification conditions of powder bed AM, yet the subsequent L1$_2$ phases that precipitate during heat treatment of the sample remain at the nanoscale, imparting high strength. For strength to be retained at elevated temperature, these nanoprecipitates must have low coarsening rates. To inversely design the composition of an alloy to have these target microstructural features, we used hybrid calculation of phase diagram (CALPHAD)-based integrated computational materials engineering (ICME) and Bayesian optimization techniques. We tested our approach by designing an Al-Er-Zr-Y-Yb-Ni model alloy, and the selected composition was manufactured in powder form as AM feedstock. The strength of specimens manufactured via laser powder bed fusion (LPBF) from the designed composition is comparable to that of wrought Al 7075, yet without cracking that occurs upon LPBF of Al 7075. After high-temperature (400$^\circ$C) aging the designed alloy is 50% stronger than the strongest known benchmark printable Al alloy.

cond-mat.mtrl-sci↗

arXiv2025

Laser-scanning of induction-melted Al alloys: are they representative of additively manufactured ones?

The bottleneck of alloy design for powder-based additive manufacturing (AM) resides in customized powder production - an expensive and time-consuming process hindering the rapid closed-loop design iterations. This study analyzed an expedited experimental workflow, i.e., multipath laser scanning of induction-melted samples, to mimic rapid solidification of AM to serve as an alternative approach to down-select from the design space. Using Al-Ni-Zr-Er model alloy, comprehensive multi-scale characterizations were performed to compare microstructural features between laser-scanned and laser powder bed fusion (LPBF) samples. Although demonstrating a difference in melt pool geometries, the microstructures in scanning electron microscopy (SEM)- and transmission electron microscopy (TEM)- scale demonstrate a high degree of similarity, in terms of microstructure morphology, grain size, presence of precipitates, and phase distribution. The mechanical performance was evaluated by microhardness tests. The results revealed a 20% reduction in laser-scanned samples compared to LPBF samples, attributed to the thermal history and potential differences in phase fractions. The decreasing trend was also observed in the benchmark alloy showing a 10% absolute error with respect to the model alloy. This study underscores the potential of this workflow to accelerate alloy design in AM by circumventing customized powder production and encourages further exploration across diverse materials and processing parameters.

physics.app-ph↗