Softening And Ductilization Of Novel Nonequilibrium Nanostructure Alloys Prepared By Working Process Of Glassy Phase

The changes in the structure,element distribution,thermal stability and mechanical properties of Al₉₀Y₁₀?90Al?and Al₈₄Y_8.5Ni₄Co₂Pd₁Fe_0.5?84Al?glassy alloy ribbons by cold rolling were examined with the aim of clarifying the difference in their properties between the simple binary alloy with crystallization processes of Amorphous?Am??fcc-Al?Al?+Am?Al+Al₃Y at the transformation temperatures of 485 K and 542 K,respectively,and the multicomponent alloy with the process of glass transition at 548 K,supercooled liquid region and then the eutectic-like precipitation of Al+cubic Al_xM_y?M=Y,Fe,Co,Ni,Pd?at 584 K.No distinct change in the exothermic peak due to crystallization is seen for the 90Al alloy even after cold rolling to about 80%reduction ratio in ribbon thickness,while the84Al alloy shows significant reduction in the exothermic amount of crystallization peak by cold rolling,showing the completely opposite tendency of structural stability between cold rolling and heating treatments.The rolling-induced Al phase was found to have the same alloy component as that for the amorphous matrix by the atom-probe analyses,being different from the heating-induced crystallization behavior.It is this noticed that the rolling-induced structure is a novel nonequilibrium Al solid solution+Am with the solute segregation-free interface for the 84Al alloy.The Al+Am structure was interpreted to be formed by the suppression of forming Al_xM_y compound through the enhancement of the instability of supercooled liquid caused by the rolling-induced strain accumulation effect.The cold-rolled 90Al and 84Al alloy ribbons exhibit good bending ductility with significantly reduced hardness.This is in contrast to the brittle and hardening nature for the heating-induced crystalline state for the 84Al alloy.The cold rolling to the 84Al glassy alloy is useful for ductilization in the metastable crystallized state for the Al-based glassy alloys with high solute contents and this novel phenomenon is promising for future extension of Al-based glassy alloys with high solute contents as structural engineering materials.