Transmission Electron Microscopy of Fe79.5B6.5C14 Network Alloys: Part II

When undercooled deeply into its undercooling regime, a molten Fe_79.5B_6.5C₁₄ ingot undergoes spinodal decomposition, splitting into two interpenetrating subnetworks which are denoted by α-(liquid subnetwork) and β-(liquid subnetwork). Transmission electron microscopy results suggest that there are three constraints on crystal growth when the undercooled, decomposed molten ingot solidifies, which are (i) the solidification is due to the advancement of a bulk solid/liquid interface. It consists of a number of α-solid/liquid interfaces moving in the α-(liquid subnetwork) and a number of β-solid/liquid interfaces moving in the β-(liquid subnetwork); (ii) to overcome two long-range composition gradients of C and B atoms; and (iii) the two long-range composition gradients stabilize the bulk solid/liquid interface. The morphology of a solidified or network Fe_79.5B_6.5C₁₄ ingot is explained in terms of the obtained microscopic results.