Microstructures, mechanical properties, and electrical resistivity of rapidly quenched Fe-Cr-Al alloys

Abstract

By the rapid quenching technique, ductile supersaturated ferrite solid solution with high hardness and strength as well as unusual electrical properties has been found in Fe-Cr-Al ternary system. This formation range is limited to less than about 35 at. pct Cr and 23 at. pct Al. The ferrite phase has fine grains of about 10 μm in diameter. Their hardness, yield strength, and tensile fracture strength increase with increase in the amounts of chromium and aluminum, and the highest values reach about 290 DPN, 720 MPa, and 740 MPa. These alloys are so ductile that no cracks are observed even after closely contacted bending test. The good strength and ductility remain almost unchanged on tempering for one hour until heated to about 923 K where a large amount of Cr2Al compound begins to precipitate preferentially along the grain boundaries of the ferrite phase. The room-temperature resistivity increases with increasing chromium and aluminum contents and reaches as high as 1.86 μ Ώ m for Fe50Cr30Al20 alloy. Also, the temperature coefficient of resistivity in the temperature range between room temperature and 773 K decreases with increasing chromium and aluminum contents and becomes zero in the vicinity of 20 to 30 at. pct Cr and 15 at. pct Al. Thus, the present alloys may be attractive as fine gauge high-resistance and/or standard-resistance wires and plates because of the unusual electrical properties combined with high strength and good ductility.