A New Investigation of the Precipitate-Nucleation using the Macroscopic Composition Gradient (MCG) Method
The critical minimum size of stable precipitate in the vicinity of edge of miscibility gap is experimentally determined for the Ni3Si in Ni-Si, Ni3Al in Ni-Al, Cu4Ti in Cu-Ti and Co in Cu-Co binary alloy systems by utilizing the macroscopic composition gradient (MCG) method recently proposed by us. The results obtained are as follows: The critical nucleus size shows a steep increase up to several tens of nm in a very narrow composition range less than 0.3at％ from the phase boundary. The diameter of nucleus size can reach over 500 nm in the composition very close to the precipitation limit. The Gibbs-Thomson relation and the conventional nucleation theory statistically rationalize such the composition dependence of nucleus size change. However, the nucleus formation is kinetically never rationalized by the conventional nucleation theories. The phase decomposition of supersaturated solid solution progresses by a mechanism of spinodal phase decomposition, even in the composition range near the solubility limit, i.e. a so-called Nucleation-Growth region. Such the phase decomposition behavior is never rationalized by the Boltzmann-Gibbs free energy which is based on the extensive entropy. The experimental facts obtained here are explained by Tsalliss non-extensive entropy.
Toru Miyazaki Takao Kozakai
Nagoya Institute of Technology, Nagoya, Japan
国际会议
厦门
英文
555-564
2006-11-08（万方平台首次上网日期，不代表论文的发表时间）