@article{jha_dulikravich_chakraborti_fan_schwartz_koch_colaco_poloni_egorov_2017, title={Self-organizing maps for pattern recognition in design of alloys}, volume={32}, ISSN={["1532-2475"]}, DOI={10.1080/10426914.2017.1279319}, abstractNote={ABSTRACT A combined experimental–computational methodology for accelerated design of AlNiCo-type permanent magnetic alloys is presented with the objective of simultaneously extremizing several magnetic properties. Chemical concentrations of eight alloying elements were initially generated using a quasi-random number generator so as to achieve a uniform distribution in the design variable space. It was followed by manufacture and experimental evaluation of these alloys using an identical thermo-magnetic protocol. These experimental data were used to develop meta-models capable of directly relating the chemical composition with desired macroscopic properties of the alloys. These properties were simultaneously optimized to predict chemical compositions that result in improvement of properties. These data were further utilized to discover various correlations within the experimental dataset by using several concepts of artificial intelligence. In this work, an unsupervised neural network known as self-organizing maps was used to discover various patterns reported in the literature. These maps were also used to screen the composition of the next set of alloys to be manufactured and tested in the next iterative cycle. Several of these Pareto-optimized predictions out-performed the initial batch of alloys. This approach helps significantly reducing the time and the number of alloys needed in the alloy development process.}, number={10}, journal={MATERIALS AND MANUFACTURING PROCESSES}, author={Jha, Rajesh and Dulikravich, George S. and Chakraborti, Nirupam and Fan, Min and Schwartz, Justin and Koch, Carl C. and Colaco, Marcelo J. and Poloni, Carlo and Egorov, Igor N.}, year={2017}, pages={1067–1074} }
 @article{jha_dulikravich_chakraborti_fan_schwartz_koch_colaco_poloni_egorov_2016, title={Algorithms for design optimization of chemistry of hard magnetic alloys using experimental data}, volume={682}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2016.04.218}, abstractNote={A multi-dimensional random number generation algorithm was used to distribute chemical concentrations of each of the alloying elements in the candidate alloys as uniformly as possible while maintaining the prescribed bounds on the minimum and maximum allowable values for the concentration of each of the alloying elements. The generated candidate alloy compositions were then examined for phase equilibria and associated magnetic properties using a thermodynamic database in the desired temperature range. These initial candidate alloys were manufactured, synthesized and tested for desired properties. Then, the experimentally obtained values of the properties were fitted with a multi-dimensional response surface. The desired properties were treated as objectives and were extremized simultaneously by utilizing a multi-objective optimization algorithm that optimized the concentrations of each of the alloying elements. This task was also performed by another conceptually different response surface and optimization algorithm for double-checking the results. A few of the best predicted Pareto optimal alloy compositions were then manufactured, synthesized and tested to evaluate their macroscopic properties. Several of these Pareto optimized alloys outperformed most of the candidate alloys on most of the objectives. This proves the efficacy of the combined meta-modeling and experimental approach in design optimization of the alloys. A sensitivity analysis of each of the alloying elements was also performed to determine which of the alloying elements contributes the least to the desired macroscopic properties of the alloy. These elements can then be replaced with other candidate alloying elements such as not-so-rare earth elements.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Jha, Rajesh and Dulikravich, George S. and Chakraborti, Nirupam and Fan, Min and Schwartz, Justin and Koch, Carl C. and Colaco, Marcelo J. and Poloni, Carlo and Egorov, Igor N.}, year={2016}, month={Oct}, pages={454–467} }
 @article{fan_liu_jha_dulikravich_schwartz_koch_2016, title={On the Formation and Evolution of Cu-Ni-Rich Bridges of Alnico Alloys With Thermomagnetic Treatment}, volume={52}, ISSN={["1941-0069"]}, DOI={10.1109/tmag.2016.2555956}, abstractNote={Despite decades of research and development of Alnico alloys, significant uncertainties in the underlying structure-property relationships remain. Here, we report on the effects of Ti on the Alnico microstructure and nanostructure, and the corresponding influence on magnetic properties. We show that Ti fosters the conditions resulting in the formation of Cu-Ni-rich bridges in the α1 phases between the α2 phases. For Alnico containing Ti, a typical chessboardlike morphology with Cu-Ni-rich bridges is observed, whereas in the absence of Ti, the α1 phases connect to each other readily, especially with a high Co concentration, and a mazelike morphology with Cu-rich white-plate precipitates rather than Cu-rich bridges is observed. Furthermore, in Alnico containing Ti, an inhomogeneous distribution of Ni is found in the α2 phases, including loops with high Ni concentration surrounding the α1 phase and high concentrations in the bridges as well. An increase in the Cu concentration is also observed in the loops around the α1 phases (Ni-Cu loops), and direct contact between the Cu-Ni-rich bridges and the Ni-Cu loops is observed in lieu of direct contact between the bridges and the α1 phases. We also observe that the bridges are not perfectly round but ellipsoidal, with the long axis along the connection of two adjacent α1 phases. The energy-dispersive X-ray spectroscopy line scans of the bridges shows that two types of Cu-Ni-rich bridges exist: those with more Cu than Ni and those with more Ni than Cu. A 3-D model is presented that explains the conditions and process of bridge formation, consistent with the observed composition distributions.}, number={8}, journal={IEEE TRANSACTIONS ON MAGNETICS}, author={Fan, M. and Liu, Y. and Jha, Rajesh and Dulikravich, George S. and Schwartz, J. and Koch, C. C.}, year={2016}, month={Aug} }
 @article{fan_liu_jha_dulikravich_schwartz_koch_2016, title={On the evolution of Cu-Ni-rich bridges of Alnico alloys with tempering}, volume={420}, ISSN={["1873-4766"]}, DOI={10.1016/j.jmmm.2016.07.040}, abstractNote={Tempering is a critical step in Alnico alloy processing, yet the effects of tempering on microstructure have not been well studied. Here we report these effects, and in particular the effects on the Cu-Ni bridges. Energy-dispersive X-ray spectroscopy (EDS) maps and line scans show that tempering changes the elemental distribution in the Cu-Ni bridges, but not the morphology and distribution of Cu-bridges. The Cu concentration in the Cu-Ni bridges increases after tempering while other element concentrations decrease, especially Ni and Al. Furthermore, tempering sharpens the Cu bridge boundaries. These effects are primarily related to the large 2C44/(C11−C12) ratio for Cu, largest of all elements in Alnico. In addition, the Ni-Cu loops around the α1 phases become inconspicuous with tempering. The diffusion of Fe and Co to the α1 phase during tempering, which increases the difference of saturation magnetization between the α1 and α2 phases, is observed by EDS. In summary, α1, α2 and Cu-bridges are concentrated with their major elements during tempering which improves the magnetic properties. The formation of these features formed through elemental diffusion is discussed via energy theories.}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Fan, M. and Liu, Y. and Jha, Rajesh and Dulikravich, George S. and Schwartz, J. and Koch, C. C.}, year={2016}, month={Dec}, pages={296–302} }
 @article{zaddach_niu_oni_fan_lebeau_irving_koch_2016, title={Structure and magnetic properties of a multi-principal element Ni-Fe-Cr-Co-Zn-Mn alloy}, volume={68}, ISSN={["1879-0216"]}, DOI={10.1016/j.intermet.2015.09.009}, abstractNote={A nanocrystalline alloy with a nominal composition of Ni20Fe20Cr20Co20Zn15Mn5 was produced by mechanical alloying and processed using annealing treatments between 450 and 600 °C for lengths from 0.5 to 4 h. Analysis was conducted using x-ray diffraction, transmission electron microscopy, magnetometry, and first-principles calculations. Despite designing the alloy using empirical high-entropy alloy guidelines, it was found to precipitate numerous phases after annealing. These precipitates included a magnetic phase, α-FeCo, which, after the optimal heat treatment conditions of 1 h at 500 °C, resulted in an alloy with reasonably good hard magnetic properties. The effect of annealing temperature and time on the microstructure and magnetic properties are discussed, as well as the likely mechanisms that cause the microstructure development.}, journal={INTERMETALLICS}, author={Zaddach, A. J. and Niu, C. and Oni, A. A. and Fan, M. and LeBeau, J. M. and Irving, D. L. and Koch, C. C.}, year={2016}, month={Jan}, pages={107–112} }