1、Shaanxi University of Science & TechnologyChapter 7 Phase transformation Lecture 1 The categories of phase transformation1. Based on the thermodynamicsFirst-order phase transformationTypes: crystal meltingcrystal sublimationliquid vaporizationCharacteristics: Accompanied with the volume change and t
2、he release of latent heat.Characteristics: No volume change and latent heatCp, , will jump at the transformation temperature.Types: Ordered-disordered transformation, ferromagnetic-paramagnetic transformation, superconducting state transformationSecond-order phase transformationThe chemical potentia
3、l and its first-order partial derivation of the system have on changes, while the second-order partial derivation of chemical potential changes.T0 TCNotes Mixed phase transformation: Phase transformation have both the characteristics of first-order and second-order phase transformation. For example,
4、 the piezoelectric ceramic BaTiO3 has a Curie point, which is theoretically a second-order phase transformation, but this ceramic also has a small latent heat, which is the characteristics of first-order phase transformation.2. Based on the particle migration Diffusional phase transformation Non-dif
5、fusional phase transformation There is a habit plane and crystal plane orientation relationship before and after the phase transformation. There is no atomic diffusion during the transformation. The transformation is very fast and the speed can reach the speed of sound. There is no specific transformation temperature, and it occurs within a temperature range. Martensitic phase transformation
