AlB_2成相过程中的反应扩散

Diffusional Reaction Mechanism during the Formation of AlB_2 Phase

采用扩散偶法研究了原位烧结过程中AlB2的形成过程及成相控制环节。扩散实验表明:铝的扩散能力远大于硼的扩散能力,Al-B体系成相主要是通过Al向B扩散实现的;Al-B可以在固-固态和液-固态下发生反应生成AlB2相;固-固态下,相互接触的Al和B通过原子间相互扩散在接触处形成固溶活化区,AlB2相便在该活化区内形成。固-固态下控制Al-B反应发生的因素是Al原子穿越反应产物的扩散能力;液-固态下控制Al-B发生反应的因素是熔融态Al对固相产物的润湿性。

A diffusion couple method was used to monitor the atom diffuseness of Al and B. Based on the classical sintering theory, the forming process of polycrystaUine AlB2 was systematically investigated. The results of diffusion experiment indicate that the diffusivity of Al is much stronger than that of B and the formation of AlB2 can be attributed to the diffusion orAl into B. The reaction between AI and B can take place at solid-solid state and liquid-solid state. In the solid-solid reaction stage, the solution activated regions form ahead at the contact areas between Al and B particles by diffusing atoms, and then AlB2 particles is precipitated from these regions. In this state, the diffusivity of AI is the crucial limit factor to the further formation of AlB2. While, in the liquid-solid reaction stage, the wetting ability of the melting AI to solid phase is the crucial limit factor.