372595889

JPRS-UMS-92-003

NONFERROUS METALS, ALLOYS, BRAZES, SOLDERS 16 March 1992

The Nitriding of a Nickel Alloy and Its Properties

927D0089N Moscow FIZIKA IKHIMIYA OBRABOTKIMATERIALOY in Russian No 6,

Nov-Dec 91 (manuscript recei\ed 30 Nov 90) pp 145-149

[Article by Yu.V. Levinskiy, A.A. Nuzhdin, V.P. Zhabin, V.B. Latyshdev, and T.L. Tsuprun, Moscow]

UDC 669.245.26.295

[Abstract] The authors of the study reportcd herein examined the process of intemal nitriding of nickel-based alloys with chromium and titanium dopants. Spe-cifically, they nitrided alloys containing the following (% by mass): chromium, 24; titanium, 0.5 to 3.0; La, 0.1; C, 0.04; and 0₂,0.05. After smelting, the ingots were forged and then rolled until sheets 1.5 mm thick were produced. Specimens were then prepared for testing in accordance with All-Union State Standard [GOST] 9657-73. A Neo-phot light microscope and Hitachi S-800 scanning elec-tron microscope were used to study the structure of the nitrided alloy specimens. The studies performed estab-lished that “through” nitriding may be achieved in the temperaturę interval from 1,373 to 1,473 K in time periods that are acceptable from a technological stand-point. Test specimens nitrided at 1,453 K were found to have a nitride phase with a characteristic particie size of 0.1 to 1.0 pm. When Iow holding times and rclatively Iow temperatures were used, the ratio of the metal elements in the nitride particles having an NaCl-type structure are approximately equal to that in the matrix. As the temperaturę of intemal nitriding is inereased, the titanium content in the particles of the hardening phase in the near-surface areas of the specimen inereases, and the chromium content decreases. According to the authors’ thermodynamic calculations, the free energy of the for-mation of complex titanium nitride (63% Ti, 17.0% Cr) at 1,173 K equals 190 kcal/mol. As the temperaturę is inereased to 1,323 and 1,453, it reaches 170 and 140 kcal/mol, respectively. Thcse elevated temperatures are also thermodynamically morę conducive to the forma-tion of phases richer in titanium. The free energy of their formation amounts to 175 and 170 kcal/mol for the specified temperatures. Intemal nitriding also resulted in significant improvements in the test specimens’ mechan-ical properties and microhardness and in a reduction in resistivity. Intemal nitriding also resulted in improved heat resistance and resistance to oxidation. Figures 4, tables 2; references 4: 3 Russian, 1 Western.

The Formation of Mg₃₂(Al, Zn)^₉ and Al-Mg-Zn Phases in an Unsaturated Aluminum-Magnesium-Zinc Solid Solution Upon Electron Irradiation in a Diffraction Channeling Modę

927D0089F Moscow FIZIKA 1 KHIMIYA OBRABOTKI MATERIALOV in Russian No 6,

Nov-Dec 91 (manuscript received 28 Sep 90) pp 50-52

[Article by V.V. Ivanov, V.M. Lazorenko, and Yu.M. Platov, Moscow]

UDC 621.791.85:620.18

[Abstract] The authors of the study examincd the formation of the phases Mg₃₂(Al, Zn)₄₉ and Al-Mg-Zn in an alloy containing 0.1% (atomie) Al and 0.06% (atomie) Zn during irradiation under a high-voltage microscope. Foils of the study alloy 0.2 mm thick were annealed in air at a temperaturę of 550° for 2 hours. The specimens were thinned in an electrolyte containing 20% HC10₄ + 80% C₂H₅OH at a temperaturę of 60°C. The foils were subjected to electron irradiation in a JEM-1000 high-voltage microscope with a power of 1 MeV at temperatures from 20 to 150°C. The intensity of the irradiation amounted to 6.2 x 10¹⁸cm'²/s, and the irradiation was performed in a channeling modę with the electron beam practically parallel to type (111), (100), and (110) planes and passing along the axes of the crystal zonę. Transmis-sion electron microscopy studies performed on the study specimens revealed that irradiation in doses of about 2.2 x 10‘²⁶/m² at a temperaturę of 100°C resulted in dislo-cation loops and zones of uniform contrast in the form of light spots with tetrahedral form vacancy accumulations inside them. The size of these zones and the tetrahedra were found to inerease as the irradiation dose was inereased; however, their density remained unchanged. Unlike aluminum-magnesium alloys, the study alloys were not found to exhibit any spatial correlation in the arrangement of the zones of uniform contrast and the tetrahedra on the one hand and the neighboring vacancy-type dislocation loops on the other. The authors were only able to speculate as to the formation mechanism of Mg₃₂(Al, Zn)₄₉ and Al-Mg-Zn phases upon electron irradiation. They hypothesizcd that it was either a seg-regation mechanism analogous to the phase formation during neutron irradiation or else a spinodal decompo-sition mechanism. Figurę 1, table 1; references 5: 3 Russian, 2 Western.

Gold Extraction With Low-Basicity Anion Exchangers

927D0030G Moscow TSYETNYYE METALLY in Russian No 6, Jun 91 pp 68-69

[Article by G.A. Stroganov, V.Ye. Dementyev, A.P. Tatarinov, D.A. Semenkov, and S.V. Valikov, Irkutsk State Scientific Research Institute of Rare Metals]

UDC 622.775:66.074.7

[Abstract] A method of regenerating saturated low-basicity anion exchanger for production of commercial gold-silver alloy containing 83 % Au by the desorption process has been devcloped. This involves treatment of the saturated anion exchanger with an alkali-cyanide solution, electrolysis of the eluate, roasting the aurif-erous carbonaceous wad, and floating-zone melting of the cinder. Treatment with aqueous NaOH-NaCN solution completes simultaneous desorption of the gold and regeneration of the low-basicity anion. A saturated anion exchanger contains typically 1.2 mg/g Au + 3.49 mg/g Fe + 0.23 mg/g Zn + 0.1 mg/g Ni + 0.1 mg/g Co + 0.04 mg/g