The magnetic field influence on magnetostructural phase transition in Ni2.19Mn0.81Ga

Magnetic properties of a polycrystalline alloy Ni$_{2.19}$Mn$_{0.81}$Ga, which undergoes a first-order magnetostructural phase transition from cubic paramagnetic to tetragonal ferromagnetic phase, are studied. Hysteretic behavior of isothermal magnetization $M(H)$ has been observed in a temperature interval of the magnetostructural transition in magnetic fields from 20 to 100 kOe. Temperature dependencies of magnetization $M$, measured in magnetic fields $H = 400$ and 60 kOe, indicate that the temperature of the magnetostructural transition increases with increasing magnetic field.Comment: Presented at the Second Moscow International Symposium on Magnetism (Moscow-2002

Training of the Ni-Mn-Fe-Ga ferromagnetic shape-memory alloys by cycling in a high magnetic field

The temperature and magnetic field dependencies of Ni-Mn-Ga polycrystals deformation are investigated. Ingots were prepared by arc-melting in argon atmosphere and further annealing. A training procedure (cycling across the martensitic transition point) for the two-way shape-memory effect was performed with Ni$_{2.16}$Fe$_{0.04}$Mn$_{0.80}$Ga samples. Changes in sample deformations were noticed with changing the magnetic field at a constant temperature. The first cycle deformation increment as compared with the initial value (in the austenitic state at zero field) in the course of the martensitic transition was 0.29%, and 0.41% and 0.48% for the second and third cycles, respectively.Comment: Presented at the Second Moscow International Symposium on Magnetism (Moscow-2002

Stress-induced transformation in a Ni-Mn-In alloy and the concomitant change of resistivity

In this work, the influence of mechanical stress on magnetic properties and electric resistance of a Ni-Mn- In alloy was studied. It is shown that compression of Ni-Mn-In polycrystalline specimens brings about a stressinduced martensitic transformation. Optical images recorded in-situ confirmed the formation of a martensitic structure during loading and back-transformation upon unloading. Unloading after deformation of specimens that had experienced compressive strains up to 6%resulted in full recovery of their resistivity and magnetic susceptibility. The sharp increase in the electric resistance caused by the stress-induced transformation opens up new possibilities for Ni- Mn-In alloys to be used as a material for sensors responding to mechanical stress

Nature of thermal hysteresis of martensitic transformation in aged Cu-Mn-A1 alloy

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

Internal Friction in Fe-Co-Ni-Ti Shape Memory Alloys

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

Microbial landscape of wounds in patients with purulent inflammatory diseases of the hand

Interpreting the results of bacteriological examination of material from wounds is a complex and crucial task for the surgeon. Detecting a pathogen in the wound does not confirm its pathogenic role, and the clinical picture of the disease often does not correspond to the obtained microbiological result. The research presents treatment data for 205 patients with purulent diseases of the hand who underwent surgery with biological samples taken for microbiological examination of the wound microflora. In Group 1 (n = 100), the microbial agent was studied by the traditional biochemical method. In Group 2 (n = 105), the combined polymerase chain reaction – mass spectrometry (PCR-MS) diagnostic method was used. In Group 1, the obtained results on the microbial flora structure of a purulent wound were comparable with published data. In Group 2, the combined PCR-MS diagnostic method allowed identifying pathogens in a shorter time, and the revealed structural features showed the predominance of gram-negative flora and fungi. © 2020, Institute of Advanced Scientific Research, Inc.. All rights reserved

Some Aspects of Structural Behaviour of Ni-Mn-Ga Alloys

The temperature induced transformation of single crystalline Ni - 31.1% Mn - 17.7% Ga (at%) shape memory alloy with Ms ~ 446 K has been studied by means of dynamic mechanical analysis (DMA), calorimetry (DSC), dilatometry, three point bending tests and TEM. Two maxima in internal friction (IF) spectra on cooling and a single maximum on heating, concurrently with kink-like anomalous changes of elastic modulus (E) have been found. Corresponding changes have been observed using the other techniques. The evolution of electron diffraction patterns and microstructure during in situ cooling and heating experiments performed in the TEM have revealed a two-stage martensitic transformation on cooling (namely, from the cubic L2, ordered parent phase (P) to a martensitic phase with a ten-layered modulated lattice (10M) and from the latter to the monoclinic distorted martensite with seven-layer type of modulation (7M) ). On heating, only one-stage transformation from 7M martensite to parent phase has been observed. The intermartensitic transformation 10M→7M and the martensitic P←→10M show the characteristics of first order transformations, such as transformation heat and transient contribution to the corresponding IF peaks

Thermal and Magnetic Properties of Stress-Induced Martensites in Ni-Mn-Ga 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