Investigator: RNDr. Antonín Dlouhý, CSc.
Number of Project: 106/09/1913
Agency: Czech Science Foundation
Duration: 01. 01. 2009 - 31. 12. 2011

The application addresses two opened questions on the relation between microstructure and martensitic transformations in NiTi shape memory alloys: (i) how the transformation path depends on chemistry and structure of grain boundaries in polycrystals, in which boundaries can be affected by processing atmospheres during heat treatments and (ii) what is the microstructural reason for pronounced changes of hysteresis loops during functional fatigue of superelastic NiTi wires. The application also focuses on one metallurgical issue which is the vacuum melting of NiTi alloys in refractory crucibles. Here the effort aims at an alloy with low oxygen content and no additional carbon contamination. Were the project granted, we may expect the following results: (i) a new insight into the relation between processing atmospheres, state of grain boundaries and the subsequent path of martensitic transformation, (ii) a microstructurally based account for changes in the fatigue behaviour of superelastic wires and (iii) set of parameters that would optimize the vacuum melting in refractory crucibles.