This article is cited in 5 papers

Mechanical properties, strength physics and plasticity

Effect of solid solution strengthening by iridium on the nucleation of dislocations in a molybdenum single crystal during nanoindentation

S. N. Dub^a, I. K. Zasimchuk^b, L. F. Matvienko<sup>b

a</sup> V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, Kiev
^b G. V. Kurdyumov Institute for Metal Physics, National Academy of Sciences of Ukraine

Abstract: The nucleation of dislocations in single crystals of molybdenum and a Mo–1.5 at% Ir solid solution has been investigated by nanoindentation. In the curve of indentation of a Berkovich indenter into the single crystals, an abrupt transition from elastic to plastic deformation has been observed at a depth of 20–40 nm due to the nucleation of dislocations in the initially dislocation-free region under the contact. Alloying of molybdenum by iridium results in a twofold increase in shear stresses under which dislocations nucleated in the contact. Therefore, the solid solution impurity of iridium in molybdenum leads to an increase not only in the plastic strain resistance (to an increase in the hardness) but also in the elastic shear stresses under which dislocations are generated (homogeneously or heterogeneously) in the contact. The latter effect cannot be explained only by an increase in the elastic moduli because of its smallness; however, it is determined to a large extent by a higher degree of perfection of the solid solution crystal as compared to unalloyed molybdenum.

Received: 08.11.2010
Accepted: 23.12.2010

 English version: Physics of the Solid State, 2011, 53:7, 1404–1411

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