Effect of Recrystallization and Phase Transitions on the Mechanical Properties of Semihard Magnetic FeCo-7.15V Alloy Dur
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TRODUCTION
THE FeCo-(7 to 14) wt pct V alloys are one of the most important groups of magnetic alloys with extensive applications in synchronous hysteresis motors (SHMs). They possess excellent magnetic properties including high Curie temperatures, high magnetizations, and low core losses.[1–4] Although these characteristics are vital for components, such as magnetic bearings and rotors, superior mechanical strength and ductility are equally important.[5] Unfortunately, mechanical properties are not well optimized yet and more efforts are being made to fulfill this goal. The FeCo alloy system has an equilibrium ordered B2 crystal structure for a wide range of compositions (29 to 70) wt pct Co and temperatures [up to ~1003 K SAEED HASANI is with the Department of Mining and Metallurgical Engineering, Yazd University, 89195-741 Yazd, Iran. Contact email: [email protected] MORTEZA SHAMANIAN and ALI SHAFYEI are with the Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan, Iran. MAJID NEZAKAT is with Acuren Group Inc., 2421 Drew Road, Mississauga, ON, Canada L5S 1A1. HOSSEIN MOSTAAN is with the Department of Materials and Metallurgical Engineering, Arak University, 38156-879 Arak, Iran. JERZY A. SZPUNAR is with the Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK, Canada S7N 5A9. Manuscript submitted May 14, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
(730 C)].[6–9] Low ductility and formability limit the application of binary ordered FeCo alloys in magnetic components.[10] It is recognized that the addition of V increases the ductility of the FeCo binary alloys due to its effect on the kinetics of atomic ordering transformation.[11,12] FeCo alloys with V lower than 3 wt pct have soft magnetic properties, while more V induces semihard magnetic properties and increases the magnetic hardness.[1,13,14] In an effort to make a trade-off between magnetic and mechanical properties, many studies have been carried out on FeCo alloys with V lower than 3 wt pct. For example, for the Fe-Co-2V alloy, Sourmail[6] showed that magnetic and mechanical properties depend only on the grain size and not on the extent of recrystallization or ordering transitions. Contradictory results were reported by Thornburg,[15] where he showed that the recrystallized fraction is the most important parameter that controls magnetic and mechanical properties. On the other hand, many investigations have been done on the effect of ordering transition on the mechanical properties. Stoloff and Davies[16] studied the mechanical properties of FeCo-2V alloys as a function of long-range order (LRO). In another study, Ren et al.[17] investigated the effect of LRO on the mechanical properties of a similar alloy and found that the yield strength decreases with cooling rate as a result of a rise in LRO degree. Also, Nabi et al.[18] correlated
the degree of order to yield strength in the FeCo-2V alloy. Moreover, they showed a significant effect of the degree of order on the frictional stress. Despite t
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