No abstract

No abstract

Homogenization treatment of as-cast Zn-16Al alloy was investigated. Effects of various parameters on the microstructure transformation and the mechanical properties were researched with the methods of hardness test, tensile test, scanning electron microscopy analysis, etc. The results indicate that 360 C Â 8 h with furnace cooling is the most reasonable homogenization process for Zn-16Al alloy. Additionally, a new kind of needle-shaped or shuttle-shaped g phase is observed during the furnace-cooled homogenization, which exhibits an extremely regular distribution with an included angle of 120 and a location between the lamellar eutectoids (a þ g). The formation of the new g phase is mainly attributed to the Al-depleted-zones left behind by the decomposition of supersaturated a phase. The a 0 phase precipitating from eutectoid reaction a ! a 0 þ g contains a much higher Al-content than that of original a phase.

Abstract

The effect of tempering on the microstructure, mechanical properties and wear resistance of cast Fe-10wt.%Cr-1.5wt.%B-2wt.%Al (referred to as Fe-Cr-B-Al) alloy after quenching at 1100• C has been investigated in the present study. The results show that microstructure of tempered Fe-Cr-B-Al alloy consists of tempered martensite, massive ferrite and discontinuous eutectic borocarbide. With the increasing tempering temperature, the retained austenite is gradually transformed into martensite. When the tempering temperature is higher than 450• C, the content of ferrite in the matrix increases gradually, however, the content of martensite decreases gradually. There was no significant change in the morphology of borocarbide. With the tempering time (4-12 h) and tempering cycle increasing, the content of ferrite in the matrix increases gradually. When the tempering temperature is lower than 450• C, the hardness of Fe-Cr-B-Al alloy has no obvious change. With the increasing temperature, the hardness gradually decreases. The hardness of Fe-Cr-B-Al alloy almost reaches the highest value after once tempering and decreases slightly after tempering for two or three cycles. With the extension of tempering time, it is beneficial to the precipitation of carbide, and the hardness of Fe-Cr-B-Al alloy increases gradually. When the tempering time is too long, the hardness begins to decrease. Fe-Cr-B-Al alloy has excellent wear resistance while quenching at 1100• C and tempering at 450 • C; the main wear mechanism is cutting wear and ploughing effect. K e y w o r d s : Fe-Cr-B-Al alloy, tempering temperature, tempering time, microstructure, hardness, wear resistance