Martensitic Transformation and Phonon Dispersion Relationship

测量了Cu-Al-Ni合金母相（< β >_1）和马氏体相（< γ >′_1,< β >′_1和< α >′_1）的声子色散关系与横向声晶格波单轴应力的关系。马氏体< γ >′_1的声子色散关系与275 MPa的单轴应力无关。此外，马氏体< γ >'_1的单轴应力诱导的< β >'_1和< α >'_1中的声子色散关系与< γ >'_1中的声子色散关系非常相似。从10k加热到A_s， < γ >′_1中的声子色散关系略有软化。施加单轴应力后，母相（< β >_1）声子色散曲线在（2/3）q_<max>和布里布鲁因带边界附近的q值处略有软化。马氏体相变被解释为孤子而不是声子的凝聚过程。马氏体相中的孪晶界是孤子。在足够高的温度下，苏氏体相由动态孤子组成。为了稳定奥氏体中的动态孤子，需要一个有限偏置场。前马氏体结构由孤子组成，孤子由与成分波动相关的偏置场稳定。马氏体相由与马氏体相变相关的偏置场绝热稳定的孤子组成。

Dependence of the phonon dispersion relation on the uniaxial stress of the transverse acoustic lattice waves, TA mode, both in the parent phase(<beta>_1) and in the martensitic phases (<gamma>'_1,<beta>''_1 and <alpha>'_1)of Cu-Al-Ni alloys were measured. The phonon dispersion relation in the martensite <gamma>'_1 was independent of the uniaxial stress up to 275 MPa. Furthermore, the phonon dispersion relations in the martensites <beta>''_1 and <alpha>'_1, which were induced by the uniaxial stress from the martensite <gamma>'_1, were very similar to that in <gamma>'_1. The phonon dispersion relation in <gamma>'_1 softened slightly by heating from 10 K to A_s. By applying uniaxial stress, the phonon dispersion curve in the parent phase (<beta>_1) softened slightly around q values of (2/3)q_<max> and of the Brillouin zone boundary.The martensitic transformation is interpreted as a condensation process of solitons instead of phonons. A twin boundary in the martensitic phase is a soliton. The asustenitic phase at sufficiently high temperature consists of dynamic solitons. A finite bias field is required to stabilize dynamic solitons in the austenite. The premartensitic structure consists of solitons stabilized by the bias field associated with the composition fluctuation. The martensitic phase consists of the solitons stabilized adiabatically by the bias field associated with the martensitic transformation itself.