Statistical analysis of grain structure evolution at heating of Nb subjected to cryogenic HPT

Abstract

Analysis of structure of niobium processed by high pressure torsion at cryogenic temperatures and its evolution at further heating has been carried out using statistical analysis methods. It was shown that the as-obtained structure is stable at room temperature. At 100 °C annealing, the recrystallization starts with formation of new group of grains. The further increase of annealing temperature up to 300 °C leads to the further development of the recrystallization process and the formation of the third grain group at. At 400 °C, the initial group of grains completely disappears, and the structure becomes completely recrystallized. Thus, one can conclude that the thermal stability of Nb processed by cryogenic HPT appears to be significantly lower than shown earlier.