One-zone rolling of composite materials

The energy–force parameters of free rolling of a strip without its tension and rolling with one backward or forward creep zone in the deformation zone are compared. The limiting backward or forward tensions are determined, and the change in the linear sizes of a composite billet during deformation in a rolling mill is considered.     

Activated sintering of W-HfC composite materials

The features of consolidation of the particles during the activated sintering of tungsten powders with different values of dispersity (d _av = 2–3 and 0.8–1.0 μm) are investigated. Sintering was activated by introducing nickel additives (up to 0.5 wt %), tungsten nanoparticles (up to 30 wt %), and finely dispersed hafnium carbide (5–30 vol %) with subsequent milling in a vibrating mill. The uniaxial compaction of the samples has been performed under pressures from 50 to 1000 MPa, and sintering was performed in vacuum at 1850°C with holding for 1 h. It is shown that the additives of tungsten carbide increase the density of sintered billets and, in combination with dispersed hafnium carbide, tungsten-based composite materials with a grain size up to 2 μm can be obtained.     

Stress distribution in antifriction composite materials

Conclusions The optimum shape of hard inclusions in a composite material, irrespective of the magnitude of load and mode of its application to the surface, is a spheroid or ellipsoid of revolution. The characteristic linear size of a hard inclusion should be greater than the calculated diameter of a single spot of contact. If a composite material is to exhibit high fatigue strength, it is necessary to ensure that the spacing between its hard and wear-resistant inclusions is not less than (1.5–2)a (a is the characteristic linear size of the inclusions).Translated from Poroshkovaya Metallurgiya, No. 11(203), pp. 54–59, November, 1979.     

Combustion products from advanced composite materials

We have established that urethane-protected N-carboxyanhydrides (UNCAs) are uniquely suited for the study of intrinsic racemization tendencies in peptide synthesis. The UNCA allows epimerization only by the direct enolization pathway (Proton abstraction from the alpha-carbon) and does not decompose upon epimerization. A protocol employing the quantitative separation and analysis of enantiomeric N-protected amino acid derivatives by chiral HPLC has been developed to measure the intrinsic rate of racemization of UNCAs under widely varying reaction conditions. The influence of the tertiary amine structure, UNCA side chain structure, and solvent were studied. The same protocol was employed to study the intrinsic rate of racemization of N-protected activated amino acid intermediates generated via 'onium-type' activating reagents. We have shown that the trends influencing the intrinsic rate of racemization of UNCAs are maintained under the conditions of in situ activations, and are consistent with the trends found in classical studies in the literature. The results are relevant to peptide synthesis both in solution and on solid phase. The intrinsic rate of racemization for any type of activation with any tertiary amine can be measured by this protocol.     

Plastic working of laminated composite materials

Conclusions Plastic working can be successfully employed for increasing the strength of the joint in a laminated composite material whose components react with each other during high-speed cladding, with the formation of brittle intermetallic compouds. At the same time, by suitable choice of reduction and mismatch, it is possible to produce straight bimetallic strips by rolling them with mismatched peripheral roll velocities.Translated from Poroshkovaya Metallurgiya, No. 12(240), pp. 47–50, December, 1982.     

Rolling of net-reinforced powder composite materials

The laws of densification zone formation in the joint rolling of metal powders and reinforcing nets have been investigated. The effect of the reinforcing net on the size of the densification zone, thickness and density of the composite strip, and rolling angle were determined for the rolling of nickel powder. Various methods for obtaining partial or complete reinforcement through the thickness of a powder rolled strip are discussed.Institute of Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(384), pp. 15–19, March–April, 1996. Original article submitted April 23, 1994.