Characterising Orientation Relationships in High Strength ultrafine-Grained Duplex Steels Using Atom Probe

Andrew J. Breen1,2, Hung-Wei Yen1,2, Mehdi Euzadjou, Vicente J. Araullo-Peters, Simon P. Ringer

1School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia;

2Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006, Australia;

e: andrew.breen@sydney.edu.au

Atom probe tomogaphy is a microanalytical tool capable of reconstructing the position and chemical identity of millions of atoms in 3D from a material specimen with sub nm spatial resolution. This comined spatial and chemical sensitivity makes atom probe tomography a potentially powerful means of characterising the chemisty and orientation relationships (OR) between ultrafine grains of important engineering materials that would otherwise be difficult to achieve with conventional diffraction based crystallography methods.

In this presentation, advanced atom probe crystallographic analysis tools will be used to study the OR between ultrafine ferrite and austenite grains of ultrahigh strength duplex steels. Of particular interest is the effect the carbon concentration has on the deviation of the Kurdjumov-Sachs (K-S) OR. The newly designed steels have medium levels of manganese (10-11 wt. %), yet yield at stresses exceeding 1 GPa, which makes these steels exciting candidates for commercial application within automobiles for imporved fule efficiency, reduced emissions and safe design.

The authors would like to acknowledge the facilities, scientific and technical support of the Australian Microscopy and Microanalysis Research Facility (AMMRF) at Sydney Microscopy and Microanalysis, at the University of Sydney.

Figure 1 – 3D Atom probe reconstruction of a high strength ultrafine-grained duplex steel containing ferrite (α) and austenite (γ) (centre). 2D density maps within each grain (top left and bottom right) reveal latent crystallographic information that can be exploited to determine the orientation relationship between the two grains.