Interactions between chemical ordering and magnetic transitions in ferromagnetic alloys.

磁性转变影响铁基合金的有序-无序转变，表现为化学有序和磁性转变。然而，很少有论文定量地讨论这些转变之间的相互作用。本文采用CALPHAD-type和BWG分析方法，研究了Fe-base和Co-base合金的有序-无序和磁转变温度，并对它们之间的相互作用进行了热力学计算。为了研究这一课题，选择了Fe-X （X: Al, Rh， Ga和Si）体系和Co-Al-X （X: Ti, Ni）体系。结果表明：(1)采用VSM、差示扫描量热法（DSC）和电阻法（ER）测定了Fe-X （X: Al, Rh, Ga, Si）二元合金的磁性和化学有序转变温度。用x射线显微分析（XMA）和透射电子显微镜（TEM）研究了有序相和无序相之间的相平衡。这些实验表明，在Fe-Al和Fe-Ga体系中存在磁序和化学序之间的相互作用。(2)通过VSM和DSC测定了Co-Al-X （X: Ti, Ni）三元合金的磁性和化学有序转变温度。用透射电镜观察了B2和D03相之间的相平衡。(3)在实验结果的基础上，采用calphad型热力学计算方法分析了Fe-Rh和Fe-Al二元体系的相平衡。综上所述，由于磁性能受到有序相的有序程度的强烈影响，因此应采用考虑磁性和化学有序相互作用的新热力学模型来精确描述相的相稳定性。

It is known that magnetic transition influences order-disorder transitions in the Fe-base alloys which show both the chemical ordering and magnetic transition. However, there are very few papers quantitatively discussing the interactions between those transitions. In the present project, the order-disorder and magnetic transition temperatures in some Fe-base and Co-base alloys has been examined and the interaction between them was evaluated by thermodynamic calculation using the CALPHAD-type and BWG analysis.In order to investigate this topic, the Fe-X (X : Al, Rh, Ga and Si) systems and the Co-Al-X (X : Ti, Ni) systems had been selected. The obtained results are as follows :(1) The magnetic and chemical ordering transition temperatures in the Fe-X (X : Al, Rh, Ga, Si) binary alloys were determined by VSM, differential scanning calorimetry (DSC) and electric resistance (ER) measurements. In the case of some alloys showing the 1st order transitions, the phase equilibrium between the ordered and disordered phases were examined by X-ray microanalysis (XMA) and transmission electron microscopy (TEM). It was clarified by these examinations that the interactions between the magnetic and chemical orderings exist there in the Fe-Al and Fe-Ga systems.(2) The magnetic and chemical ordering transition temperatures in the Co-Al-X (X : Ti, Ni) ternary alloys were also determined by VSM and DSC measurements. The phase equilibrium between the B2 and D03 phases were examined by TEM observation.(3) On the basis of those experimental results, the phase equilibria in the Fe-Rh and Fe-Al binary systems were analyzed using the CALPHAD-type thermodynamic calculation. In conclusions, it was proposed that since the magnetic properties are strongly affected by the degree of order in the ordered phase, and the new thermodynamic model which takes into account the interaction between the magnetic and chemical orderings should be used for precisely describing the phase stability of phases.