Microstructure Evolution of TiB_2/7075 Composites in Semi-Solid State near Liquids within Holding Time

摘要

Novel reactive technique has been employed in synthesis of 7075 Al matrix composites, and effect of TiB_2 particles on sedimentation and microstructure of 7075 Al Alloy in near liquidus was investigated. Researchers have shown that 4.5%TiB_2/7075 composites had the smallest grains and the minimum liquidus and solidus temperatures in 7075 Al matrix composites. 4.5%TiB_2/7075 composites holding for 21 hours appeared stratification phenomenon, the globular grains were 61μm and 214μm, 250um and 283μm with the increase of holding time respectively. The microstructures evolution of TiB_2 /7075 composites holding for different time at 635°C was a two-stage mechanism that the globular grains was formed firstly and secondly sedimentation and layering were began after a period of time of Ostwald ripening. The globular grain continued to increase during the settling process.