Abstract
The aging behavior of supersaturated Ni-10 at%Ti crystals, quenched rapidly from liquid state and solid state, has been studied. The phase transformation is investigated by means of micro-Vicker’s, magnetic balance and field ion microscopy (F.I.M.). The rate of age-hardening for the liquid-quenched (L.Q.) specimen is larger than that for the solid-quenched (S.Q.) specimen. For both the L.Q. and the S.Q. specimen the hardness decreases at about 7 ks, and then increases. The transformation kinetics is discussed by means of generalized Johnson-Mehl equation, where the ratio of transformation is estimated from the hardness and the Curie temperature. The values of time exponential n are approximately equal for the L.Q. and the S.Q. specimen, and are 0.279 (about 1/3) and 0.284, respectively. These results show that the mechanism of transformation on aging for the L.Q. specimen is as the same as that for the S.Q. specimen. Furthermore, the field ion micrographs for both the transformed L.Q. and the transformed S.Q. specimens show a modulated structure. However, the kinetic constant (k) of transformation for the L.Q. specimen is about four times larger than that for the S.Q. specimen on 873 K aging.
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