On July 15, 2025, Dr. Dawid Myszka(Warsaw University of Technology, Poland) give a lecture at NIMS as the 174th Structural Materials Seminar.
Date and Time: Thursday, July 15, 2025, 10:30-11:45
Location: Conference Room, 5th Floor, Advanced Structural Materials Building, NIMS Sengen Site
Title: Topology of retained austenite and its role in TRIP behavior of heat treated iron alloys
Speaker: Dr. Dawid Myszka, Warsaw University of Technology, Poland
Organizer: MERCER Christopher,（Additive Manufacturing Group）
Abstract:
The mechanical performance and functional behavior of Austempered Ductile Iron (ADI)are strongly influenced by the presence and stability of retained austenite within the ausferritic matrix. While the volumetric fraction and carbon content of austenite have been
traditionally emphasized, this work introduces a topological perspective by analyzing the spatial connectivity of the austenite phase and its percolation characteristics.
Using a combination of scanning and transmission electron microscopy, X-ray diffraction, magnetic measurements, and local hardness testing, we demonstrate that the transformationinduced plasticity (TRIP) effect in ADI is not solely governed by austenite content, but critically depends on the continuity of austenitic paths across the microstructure. Austenite that forms a percolating network facilitates collective martensitic transformation under mechanical or thermal activation, leading to pronounced changes in strength, ductility, and magnetic response. In contrast, a fragmented topology of austenite confines the TRIP effect to isolated zones, allowing for more gradual property evolution.
These findings offer a new framework for microstructural design of ADI through topological control of retained austenite, enabling improved performance predictability in applications involving dynamic loads or wear. The presented approach bridges phase stability,
transformation mechanics, and percolation theory, contributing to the broader understanding of metastable multiphase materials.