Yield strength anomaly in b2-ordered FeAl alloys: role of boron

• Published in: Scripta materialia 2000-06, Vol.43 (1), p.69-75
• Main Authors: Calonne, O, Fraczkiewicz, A, Louchet, F
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Dislocations; Elasticity, elastic constants; Exact sciences and technology; Intermetallic alloys; Mechanical and acoustical properties of condensed matter; Mechanical properties; Mechanical properties of solids; Metals. Metallurgy; Physics; Segregation; Yield strength anomaly
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/S1359-6462(00)00367-5

The yield strength anomaly (YSA) was observed in both Fe40Al B-free and B-doped alloys. A small addition of boron (100 at. ppm) shifts the yield stress (YS) peak 200 deg C and 175 MPa higher as compared to the B-free alloy. The characteristics of the YSA in FeAl are in accordance with those identified in many other materials. In particular, in the domain of YSA, no sensitivity to the strain rate is observed, which suggests that any modelling of this phenomenon may be built on the basis of an exhaustion /multiplication approach. The outlines of such a model are proposed, in wihc the exhaustion feature results from Yoshimi's decomposition of superdislocations driven by temperature variations of dislocation mobilities. The very strong effect of boron on YSA is explained by B-induced slowing down of dislocations, shifting to higher values the temperatures at which the < 110 > and < 100 > dislocations become mobile. Yet, a further thorough study of dislocation types and mobilities is desirable in order to support some of the assumptions of the present model.