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Martensitic Transformation in Fe-29 wt%Ni Alloy Ultrafine Particles

1995; Institute of Physics; Volume: 34; Issue: 1R Linguagem: Inglês

10.1143/jjap.34.113

1347-4065

Chen Yunhong, Deng Guichang, Huaixian Lu, Jinhui Wang, Gang Li,

Metallurgy and Material Forming

The ultrafine-particle samples of Fe-29 wt% Ni alloy with different average particle sizes (12 to 100 nm) are prepared by the evaporation condensation method in N 2 atmosphere. They exhibit a mixture of martensite α ′ (bcc) and austenite γ (fcc) phases. Each individual particle is a single crystal (bcc or fcc). The volume fraction of martensite increases markedly with the decrease of the average particle size. During heating, as the average particle size decreases, the temperature ( A s and A f ) for α ′ →γ reverse martensitic transformation decreases, and the range ( A s - A f ) of reverse transformation temperature becomes narrower, whereas during cooling (down to 77 K), we have not observed γ→α ′ martensitic transformation. The stabilization of austenite and the growth mechanism of martensite and austenite are preliminarily discussed in this paper.