UNUSUAL SOLIDIFICATION MICROSTRUCTURE OF Fe_(70)Cr_(18)Mo_2Si_1B_9 SINGLE-ROLL QUENCHED RIBBON

摘要

The solidification microstructure of Fe₇₀Cr₁₈Mo₂Si₁B₉ single-roll quenched ribbons with dif-ferent rotating speed of roller and under different atmosphere conditions was investigated.Apart from usual crystallization by homogeneous and heterogeneous nucleation,it was foundthat α-iron cohnnnar grains with strong preferred orientation formed beneath free surface andthat spheres of α-iron single coastal with a size of several μm up to 20μm,which have rarelybeen reported,appeared inside the ribbons.There was experirnental evidence suggesting thatclusters of metal atoms formed from fluctuation in early undercooled liquid might play a roleas pre-existed nuclei and,in fact,control the formation of amorphous for this alloy.