Equal channel angular extrusion compaction of semi-amorphous Al_(85)Ni_(10)Y_(2.5)La_(2.5) alloy powder

摘要

Al_(85)Ni_(10)Y_(2.5)La_(2.5) alloy powder produced by gas atomization was compacted using equal channel angular extrusion (ECAE). The powder particle size was below 40 mu m (-325 mesh grade), the powder was partially (approx 60 percent) amorphous and it contained intermetallic phases. Differential scanning calorimetry showed that crystallization of the amorphous phase starts at about 220 deg C by precipitation of Al-based f.c.c. particles and continues at temperatures above 300 deg C by formation of intermetallic phases. Four-pass B_C route compaction of the powder was conducted in a copper can at 280 deg C, to avoid additional formation of intermetallic phases and retain some level of amorphicity of the compacted material. A non-homogeneous deformation of the compacted material during ECAE process was detected. The powder was completely consolidated and no voids were observed in the regions where powder particles were severely deformed. In other regions, non-deformed round particles, cracks, and high porosity were observed. Microstructural analysis showed that the severely deformed powder particles contained amorphous and/or f.c.c. phases only, while the non-deformed and/or fractured powder particles were fully crystalline and consisted mostly of intermetallic phases.