Modelling precipitation and strength in metal alloys

By Francesco Colonna

The strength of many metal alloys changes over time, with a speed that depends on many factors, such as the composition of the alloy, the temperature applied to the material, and others. As an example, many Aluminum alloys reach a maximum strength after few hours of heat treatment at temperatures above 100 C, while their strength decreases for longer times. This behavior is associated to changes that happen in the material at a microscopic level. Indeed, over time small metallic particles, called precipitates, form, grow, and possibly disappear in the aluminum matrix. The strength of the material depends on the number, the size, and the shape of these precipitates. As they change during the heat treatment, so does the strength.

Heat treatments are routine industrial processes to increase the strength of alloys by tuning the distribution of the precipitates in the matrix. Heat treatments are also a key step in the development of new alloys. Mathematical modeling and computer simulation can give rational guidelines for the design of new alloys, reducing the time and the costs of the trial-and-error part of the work in the laboratory.

The goal of this project is to build a program software that can be used to model a large class of metal alloys, including those where a complex sequence of precipitates with different geometries is present. The research is conducted at the 3mE department of the the Delft Technical University.