Using a new simulation technique, researchers at Yokohama National University (Yokohama, Japan) were able to rapidly predict the microstructure of nickel-aluminum (Ni-Al) alloys commonly used in jet engine turbine parts.
According to the team, it has historically been time-consuming and expensive to accurately predict an alloy’s microstructure, which can greatly influence physical properties, such as strength, toughness, resistance to corrosion, hardness, and/or wear-and-tear resistance. In their research, however, the team successfully predicted alloy microstructures by using the “first-principles phase field” method.
This procedure predicts the microstructure based on the fundamental laws of physics alone, and then uses those parameters to model microstructure formations. This is contrary to empirical modeling, or predictions based on experiments or previous observations. They conducted their experiments under high temperatures mimicking those of jet engine turbines at approximately 1,027.0 °C, or 1,880.6 °F. The desired material properties at these temperatures typically require microstructure engineering based on changing several variables, such as composition, morphology, pressure, temperature, doping, casting, and forging.
A reliable simulation technique to help with the design and production of new materials based on a theoretical principle could make production faster and cheaper, according to the team. However, most of the current material design theories are phenomenological and derived from experimental observations and empirical experiences.
What makes the “first-principles phase field” method better, the researchers explain, is that it bridges the accurate small-scale calculations and large-scale models by renormalization theory. In physics, this concept essentially makes infinite degrees of freedom finite, or continuous variables discrete, they say. By using their method, they were able to overcome time-consuming and expensive procedures and still produce materials in agreement with experimental methods.
“‘First-principles phase field’ method was invented as the worldʼs first innovative multiscale simulation technique,” says Kaoru Ohno, a Yokohama professor. “Using this method, we were able to successfully predict complex microstructures of any compositions of Ni-Al alloys from first principles without using any empirical parameter, and our results agree quite well with experiments.”
Ohno and co-authors from the National Institute for Materials Science in Tsukuba, Japan, say the method can be used to predict mechanical strength of alloys, because the local force distributions and microstructures can be easily calculated.
“These studies highlight the fundamental nature of steels and other alloys that have so far only been demonstrated based on empirical observations,” Ohno says. In the future, the researchers plan to apply the method to various steel materials and other multicomponent alloys in order to predict the dependence of microstructures and local stress distributions on their initial compositions.
Source: Yokohama National University, www.ynu.ac.jp/english.