Directional solidification of Al-15% （mass fraction） Cu alloy was investigated by in situ and real time radiography which was performed by Shanghai synchrotron radiation facility （SSRF）. The imaging results reveal...Directional solidification of Al-15% （mass fraction） Cu alloy was investigated by in situ and real time radiography which was performed by Shanghai synchrotron radiation facility （SSRF）. The imaging results reveal that columnar to equiaxed transition （CET） is provoked by external thermal disturbance. The detaching and floating of fragments of dendrite arms are the prelude of the transition when the solute boundary layer in front of the solid-liquid interface is thin. And the dendrite triangular tip is the fracture sensitive zone. When the conditions are suitable, new dendrites can sprout and grow up. This kind of dendrite has no obvious stem and is named anaxial columnar dendrites.展开更多
By investigating the thermal expansion properties of three quasicrystalline alloys Al 65 Cu 20 Cr 15 quenched, Al 65 Cu 20 Cr 15 cast and Al 65 Cu 20 Fe 15 cast particles reinforced Al matrix composites from 25 ℃ to ...By investigating the thermal expansion properties of three quasicrystalline alloys Al 65 Cu 20 Cr 15 quenched, Al 65 Cu 20 Cr 15 cast and Al 65 Cu 20 Fe 15 cast particles reinforced Al matrix composites from 25 ℃ to 500 ℃, the thermal expansion coefficients of three quasicrystalline alloys were theoretically estimated. The results show that the thermal expansion coefficients of the composites are much lower than that of pure Al, and the thermal expansion coefficients of the composites reinforced by Al Cu Cr quasicrystalline particles are lower than those of the composites reinforced by Al Cu Fe quasicrystalline particles. According to estimating, quasicrystalline alloys have negative thermal expansion coefficients, and the thermal expansion coefficients of Al Cu Cr quasicrystalline alloys are lower than those of Al Cu Fe quasicrystalline alloys. In the alloys, the more the qusicrystalline content, the lower the thermal expansion coefficient.展开更多
基金Project(51001074)supported by the National Natural Science Foundation of ChinaProject(12ZR1414500)supported by Shanghai Municipal Natural Science Fund of ChinaProject(2012CB619505)supported by the National Basic Research Program of China
文摘Directional solidification of Al-15% （mass fraction） Cu alloy was investigated by in situ and real time radiography which was performed by Shanghai synchrotron radiation facility （SSRF）. The imaging results reveal that columnar to equiaxed transition （CET） is provoked by external thermal disturbance. The detaching and floating of fragments of dendrite arms are the prelude of the transition when the solute boundary layer in front of the solid-liquid interface is thin. And the dendrite triangular tip is the fracture sensitive zone. When the conditions are suitable, new dendrites can sprout and grow up. This kind of dendrite has no obvious stem and is named anaxial columnar dendrites.
文摘By investigating the thermal expansion properties of three quasicrystalline alloys Al 65 Cu 20 Cr 15 quenched, Al 65 Cu 20 Cr 15 cast and Al 65 Cu 20 Fe 15 cast particles reinforced Al matrix composites from 25 ℃ to 500 ℃, the thermal expansion coefficients of three quasicrystalline alloys were theoretically estimated. The results show that the thermal expansion coefficients of the composites are much lower than that of pure Al, and the thermal expansion coefficients of the composites reinforced by Al Cu Cr quasicrystalline particles are lower than those of the composites reinforced by Al Cu Fe quasicrystalline particles. According to estimating, quasicrystalline alloys have negative thermal expansion coefficients, and the thermal expansion coefficients of Al Cu Cr quasicrystalline alloys are lower than those of Al Cu Fe quasicrystalline alloys. In the alloys, the more the qusicrystalline content, the lower the thermal expansion coefficient.
