Fe-Ni系粉末机械合金化热力学

THERMODYNAMICS OF MECHANICAL ALLOYED Fe-Ni

参考Miedema半经验理论，建立了Fe-Ni系机械合金化（MA）过程的热力学模型．热力学计算分析指出，Fe-Ni系粉末MA过程一般不存在发生非晶化反应的化学驱动力．Fe-Ni系MA粉末由α（bcc）和γ（fcc）两相固溶体组成．在球磨过程中两相相互转化，控制这一转化的因素是形成焓的结构项．对不同球磨时间Fe60Ni40MA粉末的X射线衍射（XRD）分析，证明了所建立的热力学模型的正确性．根据XRD图确定了Fe60Ni40MA粉末在不同球磨时间的物相组成、各相成分、晶格参数、晶粒尺寸和晶格畸变等结构参数．

Fe60Ni40 powders were prepared by mechanical alloying (MA) in a planetary ball milling in argon atmorsphere. XRD analysis pointed out that the Fe - Ni MA powders consist of α (bcc) and γ (fcc) noncrystalline supersaturated solid solutions. And the two phases transformed each other during milling. In initial stage, the a phase was dominant, then it decomposed and transformed into γ phase gradually during milling. Some structure parameters of the MA powders, such as lattice parameter, grain size and lattice strain and so on, were determined by analysing the XRD patterns. A thermodynamic model of MA of Fe - Ni system was developed based on Miedema semi - experimental theory to explain the phases transformation of Fe - Ni system during milling. The thermodynamic analysis showed that there is no chemical driving force to form amorphous alloy. And what type solution or solutions presented in the MA powders during milling was controlled by structural contribution of the forming enthalpy of the alloy. All of the results are agreed with the experiments.