Speaker
Dr
Michael Hofmann
(FRM II, Technische Universität München)
Description
Austempered ductile iron (ADI) is a cast iron that has undergone a special heat treatment to greatly enhance mechanical properties. The heat treatment process of ADI consists of austenitization, quenching to a temperature between 250°C and 450°C and isothermal austempering [1, 2]. After such a heat treatment, the microstructure consists of acicular ferrite and high carbon enriched retained austenite.
The high carbon enriched retained austenite can transform to martensite during plastic deformation. The treatment parameters (austenitization temperature, austempering temperature, austempering time and alloying composition) can influence the retained austenite fraction, grain size and its stabilisation [2], which in turn will influence the deformation induced martensitic transformation.
The influence of different treatment and composition parameters on the martensitic transformation and texture formation during plastic deformation has been investigated using neutron diffraction. The combination of texture analysis and in-situ deformation tests allowed quantitative phase analysis and extraction of martensite phase fractions as a function of strain level.
The experiments allowed us to determine the influenece of austempering temperature, Nickel content and plastic strain on the martensitic transformation kinetics in ADI.
[1] L. Meier, M. Hofmann, P. Saal, W. Volk, H. Hoffmann, Mat. Char. 85 (2013) 124-133
[2] P. Saal, L. Meier, X. Li, M. Hofmann, M. Hoelzel, J.N. Wagner, W. Volk, Met. Mater. Trans A 47 (2016) 661-671
[2] Srinivasmurthy Daber et al, J.Mater.Sci (2008) 43:4929-4937
Primary author
Dr
Michael Hofmann
(FRM II, Technische Universität München)
Co-authors
Dr
Markus Hoelzel
(FRM II, Technische Universität München)
Mr
Patrick Saal
(utg, Technische Universität München)
Dr
Weimin Gan
(GEMS@MLZ, HZG)
Mr
Xiaohu Li
(FRM II, Technische Universität München)
