The Zinc Penetration Along Tilt Grain Boundary 38 deg (110) in Fe--12 at.% Si Alloy Near Ordering A sub 2 --B sub 2 in the Bulk

How the phase transition of concentration ordering in the bulk affects the process of Zn penetration along the grain boundaries in the system Fe--Si, the grain boundary wetting, and premelting transition is determined. The obtained value of the activation energy of the bulk diffusion in the ordered state significantly exceeds usual parameters of Fe and its alloys. Below the order-temperature, at which the bulk diffusion activation energy grows abruptly, the grain boundary wetting also disappears. In the alloy Fe--12 at.% Si, it is seen that above the temperatures of wetting transition T sub w a region of accelerated diffusion appears on the grain boundary in the concentration range from C sub o to C sub bt . The bulk ordering suppresses wetting and premelting on the grain boundaries. The line of the premelting transition does not reach the region of high temperatures. A protrusion directed toward low Zn content is observed on the line of premelting transition in the vicinity of the atomic ordering temperature T sub ord . Such protrusions are always formed when a line of second order phase transitions intersects a line of first order phase transitions. Graphs, Phase diagrams. 16 ref.--J.H.