MARTENSITIC-TRANSFORMATION IN ULTRAFINE FE-NI POWDERS

被引:65
作者
ZHOU, YH
HARMELIN, M
BIGOT, J
机构
[1] Centre d'Etudes de Chimie Métallurgique (CNRS), F-94407 Vitry-sur-Seine Cedex
来源
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING | 1990年 / 124卷 / 02期
关键词
D O I
10.1016/0921-5093(90)90154-U
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
The austenite ↔ martensite transformation in ultrafine FeNi powders (25-35 wt.% Ni; particle size, about 10-200 nm) was investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and differential scanning calorimetry. The ultrafine powders were prepared by levitation melting in liquid nitrogen. The as-prepared ultrafine powders were a mixture of martensite (b.c.c. α′) and austenite (f.c.c. γ). Each individual particle was a single crystal of either b.c.c. martensite or f.c.c. austenite. In contrast, bulk alloys of the same composition quenched into liquid nitrogen were found to be entirely martensitic. Austenite stabilization of some particles is probably related to the fabrication process and to the small size of the particles. It is suggested that austenite and martensite particles might be formed directly from the metallic vapours in the cold parts of the calefaction layer. On further heating, the reverse transformation of martensite to austenite occurs in the same temperature range for the ultrafine powders and for the bulk alloys. The martensite → austenite transformation was found to obey a shear mechanism. © 1990.
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收藏
页码:241 / 249
页数:9
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