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The coherent precipitates inherited by the martensite crystals change the transformation parameters. Nonmonotonous change of temperature hysteresis width of $\beta_1$$\leftrightarrow$$\gamma'$transformation versus aging time has been revealed. New approach was proposed to explain the nature of thermal hysteresis of the thermoelastic Martensitic transformations.

The anomalies of the temperature dependences of the logarithmic decrement and eigen frequency of the free damped vibrations for Fe-Co-Ni-Ti shape memory alloys were first found in the vicinity of the reverse α-γ martensitic transformation. It was shown the damping capacity in the alloys investigated is comparable with that for TiNi based alloys.

The stress-induced transformation of single crystals of Ni-Mn-Ga ferromagnetic Heusler ordered alloys to new martensitic structures has been investigated. The intermartensitic transformations, whenever they occur, were registered during heating by calorimetry, dilatometry and magnetic susceptibility measurement, showing up a step-like strain recovery, small endothermal effects, and an abrupt change of the low-field magnetic susceptibility. During intermartensitic transformations, between modulated and unmodulated lattices, as well as during the final transformation to the parent austenitic phase, noticeable anomalous changes in the specific magnetization were observed.

Deformation behavior of Ni2MnGa single crystals uniaxially loaded in compression and tension along the 〈100〉β1and 〈110〉β1axes were investigated. It was shown that three successive stress-induced structural transitions may be observed for specimens tensed along the 〈100〉β1or compressed along the 〈110〉β1direction, while only one transition was stress-induced in compression along the 〈100〉β1axis. The crystal structure of stress-induced and thermal martensite was identified and related reversible deformation values for different loading geometry were estimated.

Two successive anomalies in the temperature dependence of internal friction (IF) and elastic modulus have been detected for certain off-stoichiometric Ni2MnGa shape memory alloys both on cooling and heating between the parent and martensite phases. According to the transmission electron microscopy (TEM) observations these anomalies are related to two structural transformations, namely P→I and I→M, where I is an intermediate cubic phase obtained by <1/3 1/3 0> transverse displacement modulations of the parent P phase. As for the IF results, the I to M transformation behaves as a first order phase transition, whereas the P→I transition shows some distinctive features such as no temperature-rate dependence of the IF peak.

Methods and equipment are described for measuring the parameters of radio-navigational apparatus and for checking it at different stages of its development and production. Several components in the error of measuring the coordinates and the spatial orientation of an object are considered.

1.The presence in martensite of ?' particles precipitated during aging of austenite affects the size, distribution, and orientation of austenite sections formed in the process of the a?? transformation.2.The change in the a?? transformation mechanism due to the presence of ?' particles leads to an increase of the strength and retention of high strength in a broad range of temperatures at which martensite is aged.

Single crystals of different compositions in shape memory alloys Ni-Mn-Ga have been studied by electron and low temperature X-ray diffraction as well as by differential scanning calorimetry. It is shown that the cooling-induced martensitic phases are long-periodic ones modulated along the (110) directions by a transverse wave of atomic shifts with 5 and 7 atomic layers periodicity for the alloys studied exhibiting a martensitic transformation at 180 K and 446 K, respectively. The transformation heats appeared to be about 10 times different for both alloys.

A model incorporating soft mode behaviour into the free surface of a crystal is discussed. It is shown that Rayleigh wave with longitudinal and transverse polarization can describe the soft surface mode. The mass density change associated with this mode will allow the formation of embryos of the new phase at the surface of a crystal.

The phenomenon of electromagnetic-to-acoustic conversion (EMAC) in modulated parent and low temperature phases in monocrystalline Heusler alloy Ni2MnGa has been investigated. The anomalies in the temperature dependences of EMAC efficiency, low field magnetic susceptibility and velocities of transverse and longitudinal ultrasonic waves both at the Curie point (Tc = 347 K) and the martensitic transformation (Tm = 270 K) from one modulated phase to another are observed. A sharp decrease of the shear modulus c' near Tm has been found.

Abstract: Using powder metallurgy methods, we have produced Fe—Ni—Co—Ti alloys that have a thermoelastic martensive transformation, which is the basis of the shape-memory effect manifested by such materials. Since pores are believed to improve the shape memory, specifically the reversible nature of the strain, attention was focused on development of the technology and investigation of the characteristics of porous Fe—Ni—Co—Ti alloys. The problems that arise during sintering of such alloys from sputtered powders are due to the chemical inhomogeneity of the initial structure and of the structure formed when the liquid phase appears. Various forms of activation, such as cyclic sintering and a stepped increase in temperature, were used to prevent the liquid phase from appearing. The properties of Fe—Ni—Co—Ti alloys with a shape memory effect can be improved if the porosity is increased by obtaining larger powder grains with a more complicated shape.