Steel is still a major structural material for the transport, building and other sectors. However, it must innovate, particularly by achieving higher strengths levels as it faces competition from other materials. One method to strengthen steels is through control of precipitation hardening. Moreover, our group at IFM, Deakin University has proved through Atom Probe Tomography (APT) and High-Resolution Transmission Electron Microscopy (HR-TEM) that by controlling the temperature – time history, it is possible to form alloys with ferritic microstructure that only have solute clusters and that these can give exceptionally high strength levels.
The cluster strengthening approach has been utilised to improve bending properties of the Dual-Phase steels (ferrite-martensite microstructure), which are used for the automotive and construction industries due to their good strength-ductility balance. Bending properties of this steel has been improved by increasing the hardness of ferrite micro-constituent through formation of extremely fine precipitates (>2nm) or even solute clusters. Moreover, these clusters/nano-precipitates are stable at high temperatures, so, these steels could be processed by press forming, hot dip galvannealing, warm stamping, and welding.
This project aims to enhance steel performance through an innovative approach using clusters/interface strengthening mechanisms. A key problem with modern high strength materials used globally in the automotive and construction sectors is their limited formability. The outcome of this project will be a new microstructural concept of strengthening through fine tuning of alloy composition and using existing processing technologies to improve formability of Dual Phase steels. The benefit of this project lies in the potential to produce material that can satisfy conflicting requirements from manufactures such as safety, emission regulations, weight reduction, high strength and formability.
The project includes: 1. Alloy Design Philosophy: The composition of the Dual Phase steels is modified to (i) achieve the cluster/nano-precipitate hardening of ferrite, (ii) control austenite to ferrite transformation, (iii) refine the microstructure, and (iv) control the martensite transformation. 2. TMP Parameters Optimisation: The optimum TMP parameters are identified to (i) optimise the deformation schedule to form fine ferrite grains with cluster/nano-precipitate hardening effect, (ii) optimise cooling rate to control austenite to ferrite transformation and cluster/nano-precipitate hardening of ferrite, (iii) define the accelerated cooling temperature to form optimum volume fraction of martensite with optimum topology, and (iv) optimise coiling treatment to balance hardness of martensite and ferrite. 3. Fundamentals of the Strengthening Mechanisms: The fundamental mechanism of ferrite strengthening by cluster/nano-precipitate and martensite interface strengthening are understood by using advanced characterization techniques such as SEM-EBSD technique and advanced site-specific APT/TEM characterisation.
The project will lead to stronger and more formable Dual Phase steels, resulting in material savings and environmental benefits for applications in automotive and construction industries. This will be achieved by controlling the novel strengthening mechanisms through optimisation of steel composition and processing parameters. This innovative approach of advanced manufacturing and materials development leads to new generation steels with enhanced properties.
Dr. Ilana Timokhina is a Senior Research Academic at the Institute for Frontier Materials, Deakin University, Australia.
Dr Timokhina has 5 years’ experience in the semiconductor thin films area and over 15 years’ experience in physical metallurgy of metals and alloys. Her work involved conceiving and managing research programs of various degrees of complexity. Dr Timokhina’s key research areas are development of complex advanced high strength multiphase steels to achieve optimum material performance (two “Best Paper” awards related to this work), nano-structural materials with balanced strength and ductility produced through different severe plastic deformation processes and subsequent heat treatment, fundamental understanding of strengthening mechanisms in metals, composite and upcycling materials. She uses correlative microscopy i.e. Scanning, Transmission, Ion Beam, Electron Backscattering Electron microscopy, Atom Probe Tomography, Neutron and X-Ray diffraction as the main approach to solve scientific problems. Dr Timokhina has published more than 130 scientific papers (1792 citations, h-index 23), two book chapters, was invited speaker at many international conferences and is a reviewer for a number of international journals and grant schemes.
Dr Ilana Timokhina
Senior Research Academic
Institute for Frontier Materials, Waurn Ponds Campus, Locked Bag 20000, Geelong, VIC 3220
+61 3 52272562
Dr. Jiangting Wang is a research fellow at Institute for Frontier Materials, Deakin University. He is specialised in X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT). His previous research projects were focused on understanding the microstructure and mechanical behaviour of high-strength low-alloy (HSLA) steels, twinning-induced plasticity (TWIP) steels, and magnesium alloys. He is currently investigating the strengthening mechanism of clusters and nano-precipitates (<10 nm) in a TiMo microalloyed steel.