Novel method can predict alloy microstructures from first principles

Using a new method, Japanese researchers have rapidly and accurately predicted the microstructure of nickel-aluminum (Ni-Al) alloys, which are commonly used in the design of jet engine turbine parts. Predictions of the microstructure of these alloys have so far been time-consuming and expensive. The researchers’ findings, reported in a paper in Nature Communications, have the potential to greatly advance the design of materials made up of a range of different alloys, which are used to make products in several different industry sectors.

Alloys are durable materials made up of two or more metals. The current high cost and design limitations of traditional alloy manufacturing processes have driven the need to develop more efficient design methods. One key challenge has been how to accurately predict an alloy's microstructure (the very small-scale structure that is only visible by a microscope), as this can greatly influence an alloy’s physical properties, including strength, toughness, resistance to corrosion, hardness, and wear and tear resistance.

The researchers were able to predict alloy microstructures using the ‘first-principle phase field method’. This procedure predicts the microstructure of alloys based on the fundamental laws of physics alone (first principles) and then uses those parameters to model microstructure formations (phase field). This is in contrast to empirical modeling, or predictions based purely on experiments or previous observations. Furthermore, the researchers were able to use the method to model alloy microstructures at the high temperatures found in jet engine turbines (1027°C).

The quest for new materials with desirable properties requires microstructure engineering of materials by modifying variables such as composition, morphology, pressure, temperature, doping, casting and forging. A reliable simulation technique that can help with the design and production of new materials based on a theoretical principle could make their development faster and cheaper. However, most of the current theories of material design are derived from experimental observations and empirical data, making them both time-consuming and expensive.

What makes the first-principles phase field method so advantageous, according to the authors, is that it uses renormalization theory to bridge between accurate, small-scale (first principles) calculations and large-scale (phase field) models. Renormalization theory is a concept in physics that essentially makes infinite degrees of freedom finite, or continuous variables discrete. In other words, using their method, the researchers were able to overcome time-consuming and expensive experimental procedures, and still predict materials that were in agreement with experimental methods.

"First-principles phase field method was invented as the world's first innovative multiscale simulation technique. Using this method, we were able to successfully predict complex microstructures of any compositions of Ni-Al alloys from first-principles (basic laws of physics) without using any empirical parameter, and our results agree quite well with experiments," says Kaoru Ohno, corresponding author and a professor at Yokohama National University in Japan.

Ohno and his co-authors from the National Institute for Materials Science in Japan say the method can be used to predict the mechanical strength of alloys, because it can easily determine the local force distributions and the alloy microstructures. It can also be used to predict the microstructures of multicomponent alloys, or alloys that are made up of more than two metals.

"These studies highlight the fundamental nature of steels and other alloys that have so far only been demonstrated based on empirical observations. As such, the proposed method is a powerful theoretical tool to quickly predict the most suitable alloy that can realize the desired strength, toughness, ductility, plasticity, lightness, etc as much as possible," explains Ohno.

In the future, the researchers plan to apply the method to various steel materials and other multicomponent alloys in order to investigate the dependence of microstructures and local stress distributions on the alloys’ initial compositions, and to better understand their characteristics.

This story is adapted from material from Yokohama National University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.