Effects of processing parameters on microstructure evolutions by mechanical stirring, procedures for obtaining thixotropy in semi solid slurries, and procedure for thixoforging component, were investigated in hypereut...Effects of processing parameters on microstructure evolutions by mechanical stirring, procedures for obtaining thixotropy in semi solid slurries, and procedure for thixoforging component, were investigated in hypereutectic Al Si alloy. It is shown that 605 ℃ was the proper temperature for stirring treatment of this alloy, at which the coarse and plate primary Si crystals were effectively changed to globular crystals with a mean diameter of 200 μm after 50 min stirring, that billets with excellent thixotropy were obtained after 50 min remelting at 575 ℃, in which solid fraction of matrix and primary Si crystals was about 60%, and that a perfect near net shape component of disc casting was obtained by thixoforging.展开更多
By vacuum arc melting, lanthanum (La) was added in the range from 0.05% to 0.3% (mole fraction) to binary Ti 44%Al alloy to refine its fully lamellar (FL) colonies for high ductility. Effects of La on structures and g...By vacuum arc melting, lanthanum (La) was added in the range from 0.05% to 0.3% (mole fraction) to binary Ti 44%Al alloy to refine its fully lamellar (FL) colonies for high ductility. Effects of La on structures and grain sizes of the alloy were determined. It was observed that La greatly promoted growth of columnar grains in as cast structures of the ingots and reduced their diameters. The ingots were subsequently heat treated to obtain well defined fully lamellar structures. The material without La displayed large average size of equiaxed lamellar colonies over 1 400 μm (resulted from five measurement positions in a sample), and the material with 0.1% addition of La consisted of the finest average lamellar colonies as 381 μm, the finest grain size was 337 μm at top position. When La addition was over 0.1%, La stabilized the columnar structure and it was difficult to refine the columnar grains in heat treatment, therefore, grains were coarser.展开更多
文摘Effects of processing parameters on microstructure evolutions by mechanical stirring, procedures for obtaining thixotropy in semi solid slurries, and procedure for thixoforging component, were investigated in hypereutectic Al Si alloy. It is shown that 605 ℃ was the proper temperature for stirring treatment of this alloy, at which the coarse and plate primary Si crystals were effectively changed to globular crystals with a mean diameter of 200 μm after 50 min stirring, that billets with excellent thixotropy were obtained after 50 min remelting at 575 ℃, in which solid fraction of matrix and primary Si crystals was about 60%, and that a perfect near net shape component of disc casting was obtained by thixoforging.
文摘By vacuum arc melting, lanthanum (La) was added in the range from 0.05% to 0.3% (mole fraction) to binary Ti 44%Al alloy to refine its fully lamellar (FL) colonies for high ductility. Effects of La on structures and grain sizes of the alloy were determined. It was observed that La greatly promoted growth of columnar grains in as cast structures of the ingots and reduced their diameters. The ingots were subsequently heat treated to obtain well defined fully lamellar structures. The material without La displayed large average size of equiaxed lamellar colonies over 1 400 μm (resulted from five measurement positions in a sample), and the material with 0.1% addition of La consisted of the finest average lamellar colonies as 381 μm, the finest grain size was 337 μm at top position. When La addition was over 0.1%, La stabilized the columnar structure and it was difficult to refine the columnar grains in heat treatment, therefore, grains were coarser.
