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Renforcement d'alliages fer-aluminium ordonnés B2. Influence d'additions (Ni et B) et de la microstructure

Abstract : We study the effects of additions (Ni and B) and microstructure on the mechanical behaviour of 40 at. % Al iron-aluminium alloys. From a macroscopic point of view, we show that nickel reinforces FeAl alloys over the whole temperature range, but that it simultaneously leads to emphasize the room temperature brittleness of these alloys through a cleavage stress decrease. We confirm powder metallurgy grain refining interest to enhance yield stress as well as fracture resistance. We show that nickel-induced yield stress effect is additive to "Hall-Petch" one. Also, we point out that the strengthening phenomena (nickel or grain size) cause the yield stress anomaly, which these alloys usually present, to be hidden. Through a dislocation structures analysis of deformed materials we precise that low temperature nickel-induced solid solution hardening (SSH) can not be explained on the basis of classical SSH theories but more probably through nickel influence upon the Peierls stress. Moreover, we show that the APB tubes dragging model may be compatible with our microscopic and macroscopic results about the anomaly. Eventually, we put into relation a dynamic superdislocations multiplication process observation (in situ transmission microscopy) with the nickel-containing alloys tendency to cleavage.
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Contributor : David Colas <>
Submitted on : Monday, June 20, 2005 - 2:41:34 PM
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  • HAL Id : tel-00009539, version 1



David Colas. Renforcement d'alliages fer-aluminium ordonnés B2. Influence d'additions (Ni et B) et de la microstructure. Matériaux. Université Jean Monnet - Saint-Etienne, 2004. Français. ⟨tel-00009539⟩



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