TASS, August 25. Scientists at Samara National Research University have created an original digital model of the process of microstructure formation in aluminum alloys. It will allow to calculate the optimal parameters of thermo-mechanical treatment of alloys on the spot during production, the university's press service said on Thursday.
Production engineers need to use precise digital models of microstructure formation processes of aluminum alloys, especially its crystallographic texture. Modeling helps to optimize processing modes for the chemical composition of a specific alloy, as well as for specific products and their operating conditions. In other words, to maximize the material's useful properties and, in the future, to even develop new alloy formulations with desired properties. However, calculations using existing digital models are so cumbersome that scientists generally use supercomputers for this purpose all over the world. These models are not suitable for enterprises. Scientists at Samara University have found a way to reduce the amount of calculations severalfold, while increasing the accuracy of the calculations. They proposed their own original approaches to modeling, and this dramatically expanded the capabilities of the digital model.
"We successfully completed the main tasks of the 2018-2020 projects. First, we investigated nucleation mechanisms and recrystallization kinetics in high-magnesium alloys when running from a cast structure. And second, we developed a new method for solving the problem of selecting active sliding planes during deformation of aluminum alloys. These results allowed us to go further, and we have now completed a fundamentally important step in the development of an original mathematical model of the recrystallization of aluminum alloys during hot rolling. Software tools on its basis can already be applied at industrial enterprises," the press service quotes Evgeny Aryshensky, scientific head of the industry research laboratory of aircraft materials science (ONIL-4) at Samara University, as saying.
A group of scientists at Samara University received a three-year grant from the Russian Science Foundation (RSF) in 2018 to create mathematical models of texture formation processes in the early stages of thermomechanical processing of metals. Two groups of aluminum alloys were the object of research. The first one was with high magnesium (Mg) content. Special attention was paid to new expensive alloys with microalloying with such chemical elements as scandium (Sc) and zirconium (Zr). Development of these alloys is now actively carried out in the aerospace industry, shipbuilding, transport engineering and a number of other industries. However, many aspects of microstructure formation in these promising alloys have not yet been sufficiently studied, and this prevents them from revealing their full potential.
The results of the research made it possible to extend the grant funding in 2021 until 2023 and continue working on the finite-element model, but now the second group of aluminum alloys - those with high iron (Fe) content - was studied. Although the term of the grant is not over and the research continues, the scientists of Samara University are ready now to start implementing their results in industry.
Modeling features
In traditional finite element models of crystallographic structures, calculations are based on the principle "from the macro level to the micro level". That is, scientists first establish a general law connecting temperatures, stresses, and strains, and then use this law to calculate the development and motion of grains in the alloy.
In the model of Samara University, scientists took a different path. Calculations start from the micro level, and the general feminological law, which operates at the macro level, is automatically deduced from these calculations. The validity of the model was confirmed in the laboratory by X-ray analysis of the texture composition of the tested samples.
"The method we developed allows us to take into account complex laws of nonlinear hardening in the mathematical model. This increases the accuracy of texture composition calculations," explained project lead Sergey Konovalov, a Russian metallophysicist and professor at Samara University.
A radical reduction in the volume of calculations allows the scientists to build a more complex and adequate finite-element model. It is based on partitioning the solution domain into "ensembles" of 1,000 crystallites. No one has ever worked with such large conglomerates of grains before. After debugging on a supercomputer, programs can be run on an ordinary workstation, which greatly suits manufacturers.
"Calculations on a model with such a large conglomerate of grains is a fundamentally new way to solve the problems of texture management and obtaining a texture-free component in aluminum alloys. This, firstly, will allow us to obtain a grain structure in some aluminum alloys with high magnesium content, which enables superplastic flow without using intensive plastic deformation methods. Secondly, it will make it possible to significantly improve product quality and reduce the share of defects in production," Aryshensky noted.
For 2022-2023, it is planned to develop the model so that it takes into account the occurrence of micro-volumes with different crystallographic orientation and the formation of a cellular structure and sub-grains from them.
Development of digital twins
"Mathematical modeling of thermo-mechanical processing and microstructure formation processes in aluminum alloys is one of the prominent areas of research at Samara University's scientific school of metal physics, materials science and structural materials, which was founded by Russian Academy of Sciences member Fedor Grechnikov," said Andrey Prokofiev, First Pro-Rector at Samara University.
Four software tools developed on the basis of the new digital model have already been registered, an application has been submitted for the registration of the fifth one, and in the future there will be two more registrations. They can be used at enterprises.
"Creating digital models, digital twins, is one of the key trends of modern engineering. Samara University is developing digital twins of gas turbine engines, digital models of polymer molecules, as well as combustion processes and technological processes of unit assembly. We excel in geoinformatics, in digital modeling of the earth's surface. Since the 1970s, Samara University was one of the pioneers in developing finite element models and software tools for calculating aircraft structures," noted Prokofiev.