Research on aluminum alloys paves the way for lighter and safer vehicles

Biswajit Dalai, PhD student at Luleå University of Technology, has investigated aluminum alloys to achieve proper understanding of their performance when used in the structural components by the automotive and aerospace sectors. By examining two alloys, one conventionally used and one novel recycled, his dissertation contributes towards material development for lighter and safer vehicles.

Aluminum alloys have long been used in the body parts of cars and airplanes, and now a dissertation from Luleå University of Technology could influence how this material can be used going forward. In his dissertation, “Material Characterization of Aluminum Alloys for Automotive and Aerospace Applications”, Biswajit Dalai, doctoral student in Solid Mechanics at Luleå University of Technology, delves into the behavior of two different aluminum alloys under varied deformation conditions such as strain rate and temperature. This research could have implications in both durability and performance of the structural components produced by the automotive and aerospace industries.

"Aluminum alloys are very useful because of their high strength to weight ratio, but we need to understand their behavior at the microscopic level to predict how they will perform in real-world situations," explains Biswajit Dalai.

Great potential

The study examined the commonly used AA7075-T651 alloy which finds application in airplane components, among other things. By subjecting the material to varied deformation conditions, Dalai discovered that the inhomogeneity in the initial microstructure, that is induced by the prior manufacturing process, leads to the formation of so-called adiabatic shear bands at high deformation rates and temperatures. This phenomenon results in the cracks and subsequent failure of the material, something that is critical to understand in order to design safe and long-lasting components.

Biswajit Dalai, PhD student in Solid Mechanics at Luleå University of Technology.

Dalai also studied a recycled alloy, designated as AlSi10MnMg(Fe), produced using high-pressure die casting (HPDC). Although this relatively novel alloy manifested great potential to exhibit similar strength and ductility with respect to the conventionally used AlSi10MnMg alloy, the investigation revealed that the recycled variant has an issue in the form of discontinuous fine-grained skin layer on the casting surface. Such typical microstructure, resembling the "waves and lakes" type defect, probably arises by virtue of the casting conditions used in the HPDC process and limits the material’s durability.

"Recycled aluminum alloy has great potential for usage in the automotive industry, but first we need to properly investigate the HPDC process to understand and solve such unanticipated issues associated with it so as to fully utilize the material's potential," says Biswajit Dalai.

• Solid mechanics