Phase Evolution-Dependent Nanomechanical Properties of Al86Ni8Y6and Al86Ni6Y4.5Co2La1.5Spark Plasma-Sintered Bulk Amorphous Composites

In this work, the effects of milling and spark plasma sintering on crystalline phase evolution of Al(86)Ni(8)Y(6)and Al(86)Ni(6)Y(4.5)Co(2)La(1.5)amorphous ribbons and subsequently on nanoindentation behavior have been studied. The as-cast ribbons of both compositions exhibited three-stage crystallization behavior. The first stage of crystallization disappeared completely and onset of second stage shifted to lower values in the sintered samples compared to those in the corresponding as-cast ribbons, ascribed to evolution of various crystalline phases. The nanohardness of Al(86)Ni(8)Y(6)and Al(86)Ni(6)Y(4.5)Co(2)La(1.5)ribbons and the corresponding sintered samples were 3.26 +/- 0.59, 3.81 +/- 0.58, 6.06 +/- 0.7, and 6.14 +/- 0.82 GPa, respectively. The wear volume loss of Al(86)Ni(8)Y(6)and Al(86)Ni(6)Y(4.5)Co(2)La(1.5)as-cast ribbons at 3 mN load were 1.73 and 1.79 mu m(3), which decreased to 0.78 and 0.5 mu m(3), respectively, in the corresponding consolidated samples. The increase in nanohardness and decrease in wear volume loss in bulk samples can be ascribed to the formation of hard intermetallic phases in amorphous matrix. Average coefficient of friction for Al(86)Ni(8)Y(6)and Al(86)Ni(6)Y(4.5)Co(2)La(1.5)bulk samples at 3 mN were 0.36 and 0.32, which increased to 0.43 and 0.45, respectively, at 200 mN, attributed to the increase in the lateral force.