Automotive Materials

Jasmine Chiang

M.A.Sc. Candidate

Dept. of Mechanical and Materials Engineering
Nicol Hall, Room 303
Queen's University
Kingston, Ontario, Canada, K7L 2N8
Tel: (613) 533-3229

Email: chiangj@me.queensu.ca

Academic Background

B.Sc. (Eng) Mechanical Engineering, Materials Option - Queen's University

Current Research

Transformation-induced plasticity (TRIP) steels are a class of advanced high-strength steels that have recently attracted a lot of interest for automotive applications. These steels are strong and formable, and can therefore be used to make thinner or smaller parts, reducing the weight of the car. TRIP steels also have good crash-worthiness behaviour, which is a term that is commonly used in the automotive industry to describe the energy absorption behaviour under loading at high strain rates. These characteristics of the steel are due to the "TRIP effect," where the retained austenite phase in the microstructure transforms to a hard martensite phase when it is strained. This creates a localised work hardening effect, which delays the onset of local necking and gives improved elongation.

Jasmine's research looks at how changes in the microstructure affect the mechanical properties and the "TRIP effect". Essentially, by changing thermomechanical processing parameters, the resulting microstructures in the TRIP steel will change. An example of this is shown in the images from an optical microscope of two microstructure variants, which are labelled as equiaxed and lamellar. These two microstructures came from the same initial material, but have different final mechanical properties and different retained austenite transformation behaviour. The results of this research will help to fully characterize TRIP steel behaviour and can be used to optimize the properties of the steel so that it is well suited to each individual application, allowing for TRIP steels to be better implemented into industry.

Optical micrographs of two TRIP microstructure variants: equiaxed and lamellar. The ferrite phase is tinted blue or tan, the bainite is dark brown, and the retained austenite and martensite are white.

Publications

Chiang J., Lawrence B., Boyd J.D., and Pilkey, A.K., "Effect of microstructure on retained austenite stability and work hardening of TRIP steels," Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing, vol.528 (2011) pp.4516-4521. (doi: 10.1016/j.msea.2011.02.032)