On the martensitic structure and hardness in as-quenched Fe-Ni alloys

Abstract

The martensitic transformation in dilute Fe-Ni alloys was firstly investigated by using a composition gradient in the range from 0 to 31 mass% Ni. The current study exhibited the transformation of austenite to equiaxed or acicular ferrite at lower Ni contents can be suppressed and lath martensite can form. The electron backscattered diffraction results showed Ni has important effect on misorientation distribution in martensite. With the increase of Ni content up to ∼27.5 mass%, the misorientation distributions above 15° increased, and a peak at around 7° gradually disappeared. With the further increase of Ni content, two peaks between about 50° and 60° at low Ni contents changed into three peaks at high Ni contents and a new peak at around 17° arose due to formation of plate martensite. Moreover, it was observed that both block and sub-block was refined with increasing Ni content. Moreover, the micro-hardness/strength of martensitic Fe-Ni alloys between previous works and this work and the micro-hardness of martensite between Fe-C and Fe-Ni alloys were compared and discussed.