Structural homogeneity of nanocrystalline VT1-0 titanium. Low-temperature micromechanical properties

Abstract

The microhardness of samples of VT1-0 titanium with grain sizes ranging from 35 nm to 10 μm is measured at temperatures of 77-300 K. Nanocrystalline samples produced by rolling at low temperatures are found to be quite homogeneous, and their structure is stable with respect to thermal and mechanical interactions. The interrelationship between microhardness and grain size is well described by the Hall-Petch relationship, the parameters of which depend on temperature. Data on the temperature dependence of the microhardness and the Hall-Petch coefficient indicate that the microplastic deformation is of a thermally activated, dislocation character, regardless of grain size.

Micromechanical properties of VT1-0 titanium cryorolled to various degrees of strain

“…5 Our microhardness studies of titanium VT1-0, where the grain size was varied in the direction of size increase by annealing the initial nanocrystalline sample with d ¼ 35 nm, 12 are in qualitative agreement with the generalized Hall-Petch graph. 49 This graph has been constructed on the basis of a large number of the original and literature data and represent a straight line passing through an array of points, corresponding to the range of grain sizes from $10 lm to $10 nm.…”

“…Dependence of the microhardness of VT1-0 titanium on the grain size: (þ) the grain size was varied by cryorolling to different strains, (D) the grain size was varied by annealing to different temperatures of a sample with a grain size $35 nm. 12 …”

“…77 K has been investigated in Refs. 9-11. Previously, 12 we have investigated structural homogeneity and low-temperature micromechanical properties of VT1-0 titanium with a grain size in the range of 35 nm to 10 lm, obtained by a method described in Ref. 8.…”

High Frequency Vibrations Impact on Mechanical Properties of Nanocrystalline Titanium

“…In experiments, we employed the samples of nanocrystalline titanium of commercial purity VT1-0 produced by cryomechanical grain fragmentation (CMGF) of coarse grain material [16][17][18]. The CMGF technique consists in multiple rolling of the initial coarse-grain metal at liquid nitrogen temperature.…”

“…A large number of papers are devoted to the research into mechanical properties of nanocrystalline titanium (see [12][13][14][15][16][17][18] and the references therein). The material applicability domain depends also on the sensitivity of its mechanical characteristics to the impact of vibrations generating cyclic stresses.…”