MICROSTRUCTURE AND PHASE-TRANSFORMATION IN MELTSPUN SHAPE MEMORY ALLOYS

Abstract
The rapid solidification at the meltspinning process causes a microcrystalline structure in the ribbon-shaped semifinished products, in which the microstructure is strongly affected by the cooling-rate. Hence follows a homogeneous microstructure for copper-based alloys in every cooling-condition and a micro-segregated dendritic structure at low and intermediate cooling-rates for the Fe-Mn-based specimen. Differential scanning-calorimetry and electrical resistance provide data on the starting temperatures and the course of martensitic transformation in as-quenched and recrystallized ribbons. The incomplete martensitic transformation of the Fe-Mn-based specimens is observed by X-Ray measurements. The mechanical properties and the shape memory effect of the ribbons are compared to those of the conventionally produced material. Furthermore the effect of heat-treatments in copper-based ribbons will be described.