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Updated: Aug 24, 2026

Determining the Mechanical Strength of Ultra-Fine-Grained Metals
Published on: November 22, 2021
Abrupt discontinuity of the bulk modulus pressure dependence in Fe64Ni36
Frédéric Decremps1, Lucie Nataf
1Physique des Milieux Condensés, CNRS-UMR 7602, Université Pierre & Marie Curie, B77, 4 place Jussieu, 75252 Paris CEDEX 05, France. frederic.decremps@pmc.jussieu.fr
Abstract:
X-ray diffraction and ultrasonic measurements have been carried out simultaneously up to 7 GPa at ambient temperature on a polycrystalline sample of Fe64Ni36 Invar alloy. The bulk modulus is found to increase linearly with pressure with an unusual low value (1.4) of dB/dP up to about 3.1(2) GPa followed by a regular slope (3.6) at higher pressure. The observation of these two distinct regimes is in qualitative agreement with previous results on the variation of the iron magnetic moment, and can be interpreted using the 2gamma-state model in terms of gradual population of low spin-small volume state at the expense of the high spin-large volume state under pressure.
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