Thermal expansion of materials is of fundamental practical relevance and arises from an interplay of several material properties. For nanocrystalline materials, accurate measurements of thermal expansion based on high-precision reference dilatometry allow inferring phenomena taking place at internal interfaces such as vacancy annihilation at grain boundaries. Here we report on measurements obtained for a severely deformed 316L austenitic steel, showing an anomaly in difference dilatometry curves which we attribute to the exceptionally high density of stacking faults. On the basis of ab intio simulations we report evidence that the peculiar magnetic state of the 316L austenitic steel causes stacking faults to expand more than the matrix. So far, the effect has only been observed for this particular austenitic steel but we expect that other magnetic materials could exhibit an even more pronounced anomaly.
O.R. acknowledges funding from the Austrian Academy of Sciences via Innovation Fund Grant No. IF 2019-37. The authors A.R. and D.S. gratefully acknowledge financial support under the scope of the COMET program within the K2 Center “Integrated Computational Material, Process and Product Engineering (IC-MPPE)” (Project No. 859480). This program is supported by the Austrian Federal Ministries for Climate Action, Environment, Energy, Mobility, Innovation and Technology (BMK) and for Digital and Economic Affairs (BMDW), represented by the Austrian research funding association (FFG), and the federal states of Styria, Upper Austria, and Tyrol.
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