Speaker
Description
In the aviation industry the commercial PH15-5 steel is predominantly applied in structural parts which are subjected to strict requirements for toughness properties. Its microstructure consists of a soft martensitic matrix exhibiting a hierarchical structure consisting of so-called laths, blocks and packets. Previous work of the authors suggested that a small martensitic block size increases the cleavage fracture toughness. The block size is strongly affected by the strength of the austenite, which is dependent on its grain size and chemistry, as well as temperature. Additionally, stress fields induced by martensite formed at early stages of transformation strengthen the adjacent austenite, thereby influencing the block size of martensite formed at later stages of transformation.
Consequently, this study aims to investigate the influence of local variations of austenite grain size, chemical segregations and elastic stress fields on the martensitic block size distribution.
To this end a comprehensive set of methods comprising in-situ secondary electron microscope recordings and high temperature electron backscatter diffraction during martensite transformation, as well as electron diffraction x-ray spectroscopy measurements of regions that transformed at different times has been conducted in this work. This facilitated the distinction between the influence of prior austenite grain size, chemical segregations of especially Ni and Cr, and elastic stress fields induced by the martensitic transformation on the block size distribution of the final martensitic microstructure.
| Speaker Country | Austria |
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