原位自生TiB₂颗粒作用下偏晶Al_62.5Sn_28.7Cu_8.8 合金的液相分离规律研究

TiB₂ particles with different contents were in situ synthesized in liquid Al_62.5Sn_28.7Cu_8.8 monotectic alloy. The nucleation, growth, and migration mechanisms of the secondary liquid L₂(Sn) phase during liquid phase separation were investigated by experimental observations and theoretical analyses. When 1% TiB₂ particles were added to this ternary monotectic alloy, macrosegregation induced by liquid phase separation was significantly reduced, whereas, when TiB₂ content was further increased, there was only a little enhancement in the reduction of macrosegregation degree. Meanwhile, the secondary (Sn) phase and primary θ(Al₂Cu) phase structures were refined after TiB₂ particles were incorporated into the alloy melt. During liquid phase separation, the in situ synthesized TiB₂ particles promoted the heterogeneous nucleation of the secondary L₂(Sn) phase, resulting in the formation of a large number of L₂(Sn) droplets. In addition, TiB₂ particles restricted the diffusion growth of L₂(Sn) droplets by impeding element diffusion and droplet migration, and hindered Stokes sedimentation of L₂(Sn) droplets by changing the viscosity and density of the alloy melt as well as the droplet shape. The tensile property of monotectic Al_62.5Sn_28.7Cu_8.8 alloy was improved as TiB₂ content increased.