Orientational dependence of shape memory effects and superelasticity in CoNiGa,NiMnGa, CoNiAl,FeNiCoTi, and TiNi single crystals

The dependence of deforming stresses, shape memory effect (SME), and superelasticity (SE) on the orientation of the single crystal axis, test temperature, and disperse particle size is examined for CoNiGa, NiMnGa, CoNiAl, FeNiCoTi, and TiNi single crystals. The orientational dependence of SME, SE, and temperature interval of the development of martensitic transformations (MT) under loading and SE is established. The influence of disperse particles on magnitudes of SME, SE, and mechanical hysteresis is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 4–20, September, 2004.     

Special Features of Functional Properties of Heterophase High-Strength Ni50.2Ti37.3Hf12.5 Polycrystals and Single Crystals

Russian Physics Journal - Stress-induced B2–B19' martensitic transformations (MTs) in Ni50.2Ti37.3Hf12.5 (at.%) alloy aged at 773 K, 3 h are studied. Single crystals have lower (by 100 K)...     

Characteristics of thermoelastic martensitic transformations in heterophase ferromagnetic Ni<Subscript>54</Subscript>Fe<Subscript>19</Subscript>Ga<Subscript>27</Subscript> single crystals

Using single-crystal Ni ₅₄ Fe ₁₉ Ga ₂₇ (at.%) specimens, the effects of heat treatment, annealing at the temperatures within T = 473–1473 K for one hour followed by quenching into water, on the development of thermoelastic L2₁-L1₀ martensitic transformations is investigated. It is found out that using proper heat treatment modes one can control the temperature of L2₁-L1₀ martensitic transformations, the value of the temperature hysteresis, the critical stresses of twin boundary motion, and certain functional properties of single-crystal Ni-Fe-Ga. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 24–27, October, 2007.     

Precipitation hardening of alloys with structure modulated within the region of micro- and macroflow. I

The effect of precipitation of phase Co₃Ti on the change in mechanical properties, measured within the range of micro ( - 10^§-1), and macroflow ( = 10^–3) was studied at various stages of decomposition of the Co-Ni-Ti and Co-Ni- Ti-Al alloys. It was shown that in the region of microdeformation, a parabolic dependence () is observed, and the dependence of resistance to deformation on the grain size is expressed by Petch equation. It was shown that theoretical estimations with the use of Gerold -Haberkorn and Gleiter-Hornbogen theories are in agreement with the experimentally observed changes in macroscopic yield stress during the process of precipitation of Co₃Ti phase in the studied alloys.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 46–52, September, 1972.     

On the nature of the dispersion hardening of Cu-Al-Co alloys

The authors describe an investigation into the mechanism of strain hardening of Cu-8 at. % Al-2 at. % Co alloy strengthened by particles of the intermetallic compound CoAl. They show that within the range 77–573°K the temperature dependence of the yield point is determined by the temperature dependence of the shear modulus. At T > 573°K the reverse processes gain in importance and cause a sharp decrease in the coefficient of strain-hardening and a loss of plasticity. The investigation of the Bauschinger effect and its reversal showed that distant stresses, generated by Orowan loops, have a considerable effect on the strain-hardening process. The reversal processes and an increase in test temperature produced no qualitative change in the dislocation pattern.     

Superelasticity in Quenched and Aged FeMnAlNiTi Oligocrystals under Compression

Russian Physics Journal - The paper studies superelasticity in a 203–523 K temperature range of the 42.5Fe-34Mn-15Al-7.5Ni-1Ti at.% oligocrystals quenched and aged at 473 K for 3 hours. It is...