Crystal preferential orientation of Al-1.0%Si alloy in continuous unidirectional solidification process

Al-1.0%Si alloy rods containing unidirectional microstructures were fabricated by continuous unidirectional solidification (CUS) process. The crystal growth orientation evolution of Al-1.0%Si alloy in CUS process was studied. The microstructure was observed and the orientation results examined by electron back scattering diffraction(EBSD) indicate that at the beginning of CUS process the crystals grow along a certain preferred orientation, <100> direction, but there are also other growth directions deflecting from this preferred orientation. It is found that as directional solidification continues, the crystals with high growth speed remain and those with low growth speed vanish. The crystal preferred orientation tends to be <100> direction in competition growth process. Namely, the <100> fiber texture of Al-1.0%Si alloy rod becomes stronger in the stable directional solidification establishing process. When the solidification parameters remain stable, the crystal growth orientation also obtains in steady state. Once the technological parameters fluctuate, the stray crystals deviating from the preferred orientation appear. After the process of competition growth the crystals regain strong preferred orientation. The orientation distribution function(ODF) results also testify the above conclusions.