372595879

JPRS-UMS-92-003 16 March 1992

ANALYSIS, TESTING

17

on the curvcs plotted for the temperaturę dependence of the elasticity characteristic of solids is linked to the number of valence bonds responsible for the attractive forces between the atoms of the lattice. They then proceeded to suggest that if this hypothesis is true, the electron subsystems of A1₂0₃ and Zr0₂ contain three and four valence bonds, respectively, that play an impor-tant role in shaping the mechanical characteristics of these materials. Figures 2; references 4 (Russian).

An Investigation of Structural and Phase Transformations in Carbon Steels Subjected to the Combined EfTects of Laser Radiation and a Magnetic Field

927D0049E Moscow FIZIKA IKHIMIYA OBRABOTK1MATERIALOV in Russian No 3,

May-Jun 91 (manuscript received 12 Feb 90) pp 44-47

[Article by I.V. Suminov, Ye.V. Klopikov, N.A. Semeni-khin, S.A. Pentyuk, and Yu.A. Zasetskiy, Moscow]

UDC 539.4.019.3.621.791.85

[Abstract] Specimens of U8 Steel 15 mm in diameter and 1.5 mm thick were subjected to a senes of experiments in order to determine the structural and phase transformations occurring in them when subjected to the combined effccts of laser irradiation and a magnetic field. Before being subjected to laser hardening, the specimens were annealed in a vacuum of no worse than 10*³ Pa at a temperaturę of 750°C for 1 hour. The laser hardening was performed on a Kvant-12 unit in air with pulse energies of 0.5, 1.0, and 1.5 J and with pulse durations of 4 ms. A Polyus-600 unit was used to create a magnetic field. The magnetic induction lines were oriented coax-ially to the laser radiation, and the magnetic induction on the specimens* surface was approximately 0.5 T. A YaGRS-4M spectrometer, gas-discharge detector, DRON-3M diffractometer, and Metalplan microhard-ness tester (manufactured by the firm Leitz) were used to study the laser radiation- and magnetic field-induced changes in the Steel specimens. The Mossbauer spectra of all of the specimens tested were found to cxhibit the characteristic sextet of lines corresponding to marten-site. The Mossbauer spectra of those specimens that were not treated in a magnetic field were found to exhibit an additional central singlet associated with the presence of residual austenite in the surface layer. Disordering of the position of the carbon atoms in the martensite lattice following the treatment was found to cause a broadening of the lines constituting the scxtet. In the absence of a magnetic field, the amount of residual austenite increased as the power of the laser pulse was increased, and a weak disordering of the carbon atoms could be observed. When a magnetic field was applied, residual austenite was absent. As the power of the laser radiation was increased, increasing disordering of the carbon atoms in the martensite could be observed. A layer-by-layer analysis of the specimens treated at the max-imum radiating power with no magnetic field showed

that the amount of residual austenite decreased deeper into the specimens. In the case of specimens irradiated in a magnetic field, the maximum disordering of the carbon in the matrix occurs at a depth of about 10 pm. X-ray crystallographic analysis confirmed these results. The application of a magnetic field at the moment of irradiation was found to increase specimens’ microhardness somewhat; however, a magnetic field did not alter the basie profile of microhardness throughout the depth of the individual specimens treated. This increase in microhardness after the application of a magnetic field was attributed to the fact that the resultant elimination of residual austenite resulted in a greater relative amount of martensite in the treated specimens and thus in a corresponding increase in their microhardness. Fjgures 2; references 9: 8 Russian, 1 Western.

An Investigation of the Destruction of Composites by Laser Radiation in a Vacuum and at Atmospheric Air Pressure

927D0049D Moscow FIZIKA I KHIMIYA OBRABOTKIMATERIALOY in Russian No 3,

May-Jun 91 (manuscript received 4 Apr 90) pp 38-43

[Article by V.T. Karpukhin, M.M. Malikov, N.V. Mona-khov, A.P. Chemyshev, and N.I. Shalnova, Moscow]

UDC 539.4:678.067

[Abstract] The authors of the study examined the destructive effect of laser radiation on composites in a vacuum and at atmospheric pressure. A continuous-wave C0₂ laser with an emissive power of up to 20 kW served as the radiation source. The pressure in the test chamber was varied from 1.3 x 10² to 10⁵Pa, and the specimen exposure time was varied from 1 to 20 sec-onds. A rectangle measuring 45 x 45 mm was irradiated in each specimen, and the power-flow density at the irradiated spot reached 10³/cm². In a number of the experiments performed, a focusing lens madę it possible to achieve a power-flow density of 0.5 to 1 x 10⁴ W/cm². Type STK glass-reinforced plastic, a carbon-plastic com-posite, and porous chlorosulfonated polyethylene with a filier served as the test composites. When materials of the same class as the test composites are subjected to irradiation at a radiating power of about 10³ W/cm² or less in atmospheric air, the predominant mechanisms of their destruction are thermal decomposition of the binder and the emission of solid coke particles in the form of gaseous produets. The formation of these particles has been attributed to the destruction of the porous skeleton of the coke under the effect of thermal and mechanical loads during the filtration of pyrolysis gases. The experiments reported herein confirm that these same two mechanisms are the main mechanisms of the destruction of the type STK glass-reinforced plastic and carbon plastic composites tested. Decomposition of the binder makes a greater contribution to mass entrainment than particie emission does. Other researchers have shown that thermomechanical actions also affect the