An in situ reaction and spray forming technique were employed in the synthesis of 2% TiB2/Si-30Al composite.The formation mechanism of TiB2 particulates was explained based on thermodynamic theory.The modification of ...An in situ reaction and spray forming technique were employed in the synthesis of 2% TiB2/Si-30Al composite.The formation mechanism of TiB2 particulates was explained based on thermodynamic theory.The modification of the primary Si in the Si-30Al alloy was interpreted in the light of the knowledge of atomic diffusion.The experimental results show that adding 2% TiB2 to the Si-30Al alloy can effectively refine the primary Si.Moreover,the coarsening and growth of primary Si phase in its semi-solid state was retarded effectively due to the existence of the TiB2 particulates.展开更多
In long-term rheological shear experiments with semi-solid alloys, coarsening of the particles will falsify the interpretation of the experimental results.The coarsening is intensified by the shear induced convection ...In long-term rheological shear experiments with semi-solid alloys, coarsening of the particles will falsify the interpretation of the experimental results.The coarsening is intensified by the shear induced convection and the mean size of the particles is changed significantly during the experiments.A simple model has been set up which takes the influence of the convection into account.The resulting growth law has been simplified for diffusion and convection dominated growth.The growth law was verified with shear experiments in a Searl-rheometer with A356 and tin-lead alloys.The experiments demonstrated that under convection the growth follows a linear time law and that the rate constant depends on the root of the shear rate.The correction of experimental results to gain the true viscosity function is demonstrated for a shear jump experiment with A356.展开更多
基金Project(707007)supported by the Cultivation Fund of the Key Scientific and Technical Innovation,ChinaProject(2093040)supported by Beijing Municipal Natural Science Foundation,China
文摘An in situ reaction and spray forming technique were employed in the synthesis of 2% TiB2/Si-30Al composite.The formation mechanism of TiB2 particulates was explained based on thermodynamic theory.The modification of the primary Si in the Si-30Al alloy was interpreted in the light of the knowledge of atomic diffusion.The experimental results show that adding 2% TiB2 to the Si-30Al alloy can effectively refine the primary Si.Moreover,the coarsening and growth of primary Si phase in its semi-solid state was retarded effectively due to the existence of the TiB2 particulates.
文摘In long-term rheological shear experiments with semi-solid alloys, coarsening of the particles will falsify the interpretation of the experimental results.The coarsening is intensified by the shear induced convection and the mean size of the particles is changed significantly during the experiments.A simple model has been set up which takes the influence of the convection into account.The resulting growth law has been simplified for diffusion and convection dominated growth.The growth law was verified with shear experiments in a Searl-rheometer with A356 and tin-lead alloys.The experiments demonstrated that under convection the growth follows a linear time law and that the rate constant depends on the root of the shear rate.The correction of experimental results to gain the true viscosity function is demonstrated for a shear jump experiment with A356.
