Dissertation Defence: Improvement of Thermal and Electrical Conductivity of the A356 Aluminum Alloy via Heat Treatment
November 9 at 9:00 am - 1:00 pm
Kyle James Lessoway, supervised by Dr. Lukas Bichler, will defend their dissertation titled “Improvement of Thermal and Electrical Conductivity of the A356 Aluminum Alloy via Heat Treatment: Effect on Mechanical and Tribological Properties” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mechanical Engineering.
An abstract for Kyle James Lessoway’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. Registration is not required for in-person exams.
Abstract
As global emission standards become more stringent, the automotive sector continues to aim for vehicle mass reduction and powertrain efficiency enhancement to meet future vehicle emissions targets. In the case of electric vehicles, improving the electrical conductivity of motor housings can minimize eddy-current losses, whereas in internal combustion engine materials, increasing their thermal conductivity is essential to enable increased engine pressures and temperatures. The A356 aluminum-silicon casting alloy is widely used for automotive components due to its superior electrical conductivity compared with other aluminum alloys. However, traditional heat treatment protocols have been developed to prioritize the alloy’s mechanical strength.
This study focused on the optimization of the traditional T6 heat treatment, consisting of three stages: solution heat treatment (500 – 550 °C), quenching, and artificial aging (150 – 210 °C), followed by examining the impact of the T6 heat treatment on the alloy’s tensile strength, high-temperature thermal and electrical conductivities, and wear resistance.
The results demonstrate that while higher temperature solution heat treatment and lower temperature artificial aging treatments achieved desired hardness improvements of 86% and improved tensile properties for many industrial applications, compared to the as-cast alloy. Higher-temperature artificial aging treatments significantly enhanced wear resistance and conductivity. Alloy samples subjected to modified T6 heat treatments (with a priority on optimizing thermal and electrical conductivity) exhibited a 21 % increase in electrical conductivity, a 9 % increase in thermal conductivity, and a 30 % increase in wear resistance. However, no single heat treatment regimen maximized all properties simultaneously. These improvements were attributed to the refinement of the eutectic silicon phase and the accelerated precipitation of the Mg2Si phase during the modified heat treatment. The wear resistance was enhanced by reduced crack initiation at the interface between the tribo-layer and the matrix substrate, primarily due to the refinement of the eutectic silicon and the formation of coarse Mg2Si precipitates.
