Quenched-in Vacancies and Hardening of Fe-Al Intermetallics

I. Prochazkaa, T. Vlasaka, J. Cizeka, F. Lukaca, b, M.O. Liedkec, W Anwandc, Y. Jiraskovad, D. Janickovice aFaculty of Mathematics and Physics, Charles University, V Holesovickach 2, 180 00 Praha 8, Czech Republic bInstitute of Plasma Physics of the Czech Academy of Sciences, Za Slovankou 3, 182 00 Praha 8, Czech Republic cInstitute of Radiation Physics, Helmholtz Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany dInstitute of Physics of Materials, Academy of Science of the Czech Republic, Žižkova 513/22, Brno 61662, Czech Republic eInstitute of Physics, Slovak Academy of Science, Dubravska cesta 9, Bratislava 84511, Slovak Republic

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The role of vacancies in hardening of Fe-Al intermetallic alloys were studied in the present work for a wide range of Al concentrations from 20 to 50 at%. The alloys quenched from 1000° as well as those annealed subsequently at 520° for 1 h were subject to study. Slow-positron beam experiments combined with Vicker's microhardness tests were utilised. Hardness of Fe-Al alloys exhibited a somewhat complex dependence on Al content which could not be fully explained purely by consideration of intermetallic phases formed. This happens due to additional hardening effect caused by quenched-in vacancies. The concentrations of vacancies were estimated from positron back-diffusion data and found to rise for Al content above 25 at%. Correlation of vacancy concentrations with hardness data for the quenched and annealed alloys has revealed that hardening of alloys with a low Al content (<30 at%) is originated predominantly by anti-phase boundaries while hardening induced by quenched-in vacancies dominates for alloys with a higher Al content (30-50 at%).

DOI:10.12693/APhysPolA.137.255 topics: positron annihilation spectroscopy, intermetallics, vacancies\\vs*{14pt}