激光熔覆铜基合金涂层中的液相分离行为

Liquid phase separation behaviors in Cu-base alloy coatings formed by laser cladding

为了研究铜基合金激光熔覆中的液相分离行为,根据液相分离理论在ZL104铝合金表面成功制备了具有液相分离特性的铜基合金涂层,并采用扫描电镜等对涂层中液相分离形成的分离相(硬质强化相)的形态特征与分布规律进行了观察,研究了不同分离相的形成机制与液相分离行为.研究表明,涂层中的分离相通常呈弥散分布和偏聚2种典型形态.熔池温度较高时分离相表现出"富Mo核心+包围相"的2层复合结构,呈边缘粗糙的不规则近球状形貌,这是由异质形核诱发的液相分离所形成的;温度稍低时强的表面能约束则是影响液相分离的主要因素,并使分离相呈光滑球状形态.当表面能过高时在对流等因素作用下分离相间会发生严重的碰撞凝并,最终形成大块偏聚体.

To study the liquid phase separation behavior of Cu-base alloys, such coatings on ZL104 aluminum alloy substrates were fabricated by laser cladding. A scanning electron microscope was utilized to observe the morphologies and distributions of the separate phases （ strengthening phases）. Formation mechanism and liquid phase sepa- ration behavior of these phases were also studied. The results showed that the separate phases are distributed in two typical forms, one in dispersion and the other in clustering. When the temperature of the molten pool is high, the separate phases, which are formed by heterogeneity nucleation, take on a two-layered composite structure with a ＂Mo-rich core ＋ surrounding phase＂ , showing an irregular near-spherical appearance with coarse surface. At low- er temperatures, the surface energies become the main factor determining the morphologies of separate phases and allow the separate phases to become smooth spheres. Convection in the molten pool results in the coagulation of separate phases, leading to the formation of cluster when the surface energy is high enough.