Structure and thermal stability of submicron-grained molybdenum

The structure and thermal stability of submicron-grained molybdenum produced by severe torsional plastic deformation under quasi-hydrostatic pressure were studied. The structure with a grain size of 20-100 nm formed upon deformation is characterized by strong lattice distortions (the root-mean-square value of the distortions is equal to 12 x 10 -3 ) ; the hardness of submicron-grained molybdenum is equal to 5.8 GPa. Heating to 900°C leads to a slight increase in the hardness (to 6.2 GPa) and virtually complete relaxation of the lattice distortions. Heating in a temperature range of 1000-1100°C leads to an abrupt increase in the grain size and a decrease in the hardness (to 2 GPa).