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J. Pörnbacher, H. Leitner, P. Angerer, T. Wojcik, S. Marsoner, G. Ressel:
"TiC-(Ti,M)C core-rim structures in solid-state manufactured steel-based MMCs";
Materials Characterization, 156 (2019), 109880; S. 1 - 8.

Core-rim structures in TiC-based metal matrix composites are known to be an important microstructural feature
influencing the mechanical properties of the material. While this is a widely investigated topic for metal matrix
composites consolidated by techniques utilizing a liquid phase, little research is available for core-rim structures
in solid-state manufactured TiC-steel composites. In this work we study core-rim structures of 10 vol% TiC
particles in a heat-treatable steel matrix, solid-state consolidated at 1140 °C by hot isostatic pressing. Before
consolidation, TiC and steel powders were mixed by either tumble blending or attritor milling, which allows
characterizing the influence of TiC particle size on the core-rim structure. SEM and STEM/EDS microstructural
investigations show that in both materials a rim phase of the type (Ti,M)C (M = V, Mo, W, Cr) forms during
solid-state consolidation and heat treatment. It is thereby shown that TiC in steel-based composites can be
thermodynamically instable and form a core-rim structure even in the absence of a liquid phase. While significantly more (Ti,M)C forms in the attritor milled sample, it is less enriched in matrix elements compared to the
tumble blended sample. Comparing thermodynamic calculations with the amount and composition of (Ti,M)C
formed, it is shown that the attritor milled composite is much closer to thermodynamic equilibrium of matrix
steel + 10 vol% TiC than its blended counterpart. Moreover, it is found by TEM and XRD that the rim phase has a
NaCl crystal structure and grows epitaxially on the surface of original TiC particles

Metal matrix composite Titanium carbide Hot isostatic pressing Core-rim structure

http://dx.doi.org/10.1016/j.matchar.2019.109880