Microstructure and mechanical properties of partially amorphous Al85Y8Ni5Co2 plate produced by spray forming

Abstract

A 12mmthick Al85Y8Ni5Co2 plate was spray deposited on a 30mmthick copper substrate pre-heated to 383 K. The deposit microstructure consists of an amorphous phase, 50–150nm fcc-Al grains, 0.2–0.7m Al2Y and Al3Y intermetallic phases and some unidentified phases. The hardness of different microstructural features and the compressive strength of the deposit, after extrusion at 723 K, were evaluated. The small size overspray particles as well as the deposit show a glass transition phenomenon. The total crystallization energy of the deposit is 121 J/g compared to 83.9 J/g for the small sized overspray powder, indicating its high metastability. A compressive strength of 925MPa and a deformation strain of 9% were achieved for the deposit after extrusion. The novel microstructural features in the deposit are attributed to the “chilling effect” on highly undercooled or partially solidified large-size droplets during deposition onto the pre-heated substrate, and the rapid heat extraction thereof due to a close contact at the deposit/substrate interface.