B.A. Movchan

Structure and property relationships in microlaminate Ni-Cu and Fe-Cu condensates☆

Abstract Microlaminate metal matrix composites offer considerable potential as high strength high toughness materials with isotropic properties in the plane of the sheet. In this paper we deal with the preparation of Fe-Cu and Ni-Cu microlaminate composites by electron beam evaporation from two sources and alternating deposition onto a rotating substrate. The thickness of the laminae was varied by changing the evaporation rates of the metals and the speed of rotation of the substrate. The deposits were characterized by optical microscopy, scanning electron microscopy and electron microprobe analysis to study the thicknesses of the laminae and interdiffusion of elements between the layers. X-ray diffraction was used to study the composition of the laminates. The microhardness and tensile strength at room and high temperatures of the laminates were studied and correlated with the thicknesses of the laminae and the microstructure. The results showed very marked increases in strength and hardness as the size of the laminae decreased below about 2 μm. Superplastic behavior was observed at a certain thickness of the laminae, strain rate and temperature.

Structure-property relationships in microlaminate TiC/TiB2 condensates

Abstract This is the fourth of the series of papers on microlaminate materials prepared by evaporation techniques. The first two papers dealt with Cu/Ni, Cu/Fe, Ti/Ni and Cr/Cu microlaminate condensates, which are metal/metal systems, and the third dealt with the metal/ceramic system Ni/TiC. In this paper we present the results of our investigations on structure-property relationships in the ceramic/ceramic microlaminate composite TiC/TiB 2 . The composites were prepared at the Paton Electric Welding Institute and studied at the University of California, Los Angeles. The thickness of the composite sheet was 0.25–0.30 mm and the lamina thickness was varied in the range of 0.15–5μm. The microstructure and phases present were studied by microscopic and diffraction techniques whereas bend tests were used to study the mechanical properties.

Structure and properties of refractory compounds deposited by electron beam evaporation

This work reports on the structure and properties of the refractory compounds TiC, ZrC, TiB2, ZrB2, TiCZrC, TiCTiB2 and TiCTiB2 Co. The deposits were prepared by direct evaporation of TiB2, ZrB2, ZrC, TiC and cobalt from single and multiple water-cooled copper crucibles using electron beam heating. TiC and ZrC deposits were also prepared by the activated reactive evaporation process. The vapors were condensed on a molybdenum or tantalum substrate at various deposition temperatures ranging from 650 to 1600 °C. The deposition rate was varied from 0.08 to 6 μm min−1 The deposits were characterized by optical microscopy, scanning and transmission electron microscopy, X-ray and electron diffraction and microhardness determinations. With direct evaporation the deposits contained decomposition products in addition to the parent phases. The composition of the deposits was dependent on temperature of deposition, composition of the evaporant billet and to a small extent the rate of deposition. Deposition temperature, rate of deposition and the composition of the deposit influenced the preferred orientation and the microhardness of the deposits. Surface and fracture cross section morphology and microstructure varied with deposition temperature. The data represent an extensive characterization of refractory compound deposits made by high rate physical vapor deposition processes.

Structure and properties of refractory compounds deposited by direct evaporation

Abstract This paper reports on the structure and properties of refractory compound deposits of TiB 2 , ZrB 2 , ZrC, 55% TiB 2 −45% ZrB 2 and 60% ZrC−40% ZrB 2 . The deposits were prepared by direct evaporation of TiB 2 , ZrB 2 and ZrC from water- cooled copper crucibles using an electron beam as the heat source. The vapors were condensed on a Mo substrate which had a temperature gradient ranging from 650°C to 1600°C. The deposition rate was 1–3 μm min -1 , and the thickness ranged from 25 to 75 μm. The deposits were characterized by optical and scanning electron microscopy, X-ray diffraction analysis, energy-dispersive analysis and microhardness determinations.

Structure-property relationships in Cr/Cu and Ti/Ni microlaminate composites

Abstract Cr/Cu and Ti/Ni microlaminate composites were deposited as full density sheets from two electron beam evaporation sources. The deposits were characterized by X-ray diffraction, optical microscopy and scanning electron microscopy. Microhardness and tensile properties were measured at room and elevated temperatures as a function of lamina thickness. The strength increased markedly in the range of lamina thickness below 10 μm. The specimens showed brittle behavior at room temperature but exhibited some ductility in elevated temperature tests.

Preparation and properties of TiC/Ni microlaminates☆

Abstract This is the fifth paper in a series of papers on microlaminate composite materials prepared by evaporation techniques. Earlier studies dealt with metal/ metal, ceramic/ceramic and metal/ceramic microlaminate condensates. This investigation is an extension of the earlier work on metal/ceramic (Ni/TiC) composites. The relationship between the ultimate tensile strength and the laminate layer thickness at a constant metal-to-ceramic ratio is studied. The nickel layers were produced by direct evaporation and the TiC layers were produced by activated reaction evaporation. The microstructure and phase analysis were studied using microscopy and X-ray diffraction techniques. Tensile tests were carried out at room temperature and at 600 °C on sheet specimens. The results revealed that the strength increased as the laminate layer thickness decreased.

Control of the structure and mechanical properties of thick vacuum condensates using dispersed particles

Abstract This work summarizes the results of investigations of the structural and mechanical properties of two-phase condensates obtained by the simultaneous electron beam evaporation from independent sources of metals (nickel and iron) and of non-metallic materials (oxides, carbides and borides). The mechanical properties are considered in relation to the substrate temperature, the particle diameter, the second phase content, interphase interactions at the particle-matrix material interface and the grain size of the metallic matrix. An extension of the mechanism that controls the strength and ductility of two-phase condensates of the dispersion-strengthened type is presented.

Effect of substrate temperature and amount of strengthening phase on density and mechanical properties of thick Ni-ZrO2 condensates☆

Abstract Dispersion-strengthened Ni-ZrO2 condensates 1–2 mm thick were produced by separate electron beam evaporations of nickel and the strengthening addition of ZrO2 from self-contained sources in a vacuum of 1 × 10-4 - 5 × 10-5 Torr. Deposition of the vapor mixture was performed at substrate temperatures of 650, 850 and 1100 °C; this allowed us to vary the size of the ZrO2 particles between 120 and 1300 A. The content of the second phase varied between 0 and 6 vol.%. The density of the two-phase condensates was determined as a function of substrate temperature and the amount of the second phase. The short-time tensile properties of the condensates were studied at test temperatures of 20, 700 and 1000 °C. The dependences of the density and mechanical properties of the condensates on substrate temperature and the amount and size of the second phase particles were established. The yield strengths of two-phase condensed materials are discussed on the basis of Orowans dislocation model as modified by Ashby. It is shown that the 0.2% offset yield strength of two-phase Ni-ZrO2 condensates at 20 °C can be expressed by the relation σ0.2 = σOR + 1.35 × 103f, where σOR = 2τ, τ is the yield strength according to Orowan and f is the volumetric fraction of ZrO2.

Production of protective coatings by electron beam evaporation

Abstract In this paper we briefly describe the principles and technological feasibilities of three methods of electron beam evaporation of materials: direct electron beam evaporation, activated reactive electron beam evaporation and electron ion evaporation. The advantages and drawbacks of electron beam vapour phase technology are discussed with respect to the deposition of corrosion-resistant, heat-resistant and wear-resistant coatings. Examples of electron beam equipment for deposition of these coatings in continuous and batch operation are given. It is emphasized that the electron beam evaporation of metallic and non-metallic materials should be considered as the most physicochemically precise set of methods for designing composite coatings of dispersed or laminar type, which cannot be deposited by other methods. The effect of structural parameters and interphase interactions on the strengthening and plasticity of coatings of the dispersion-strengthened type is studied. Further progress in the creation of protective coatings using electron beam evaporation should be based on the development of composite materials with special properties and on the simultaneous improvement of electron beam equipment and reduction in its cost.

Investigation into the effects of the nature, the size and the number of particles on the structure and mechanical properties of thick iron-based dispersion- strengthened condensates

Abstract We investigated the structure and mechanical properties of thick (0.8–1.5 mm) vacuum condensates of iron and their dependence on the volumetric content of the strengthening additives Al 2 O 3 , ZrB 2 , TiB 2 , NbC or TiC. The amount of the second phase present in the iron reached 2 vol.% for the oxides and 8–13 vol.% for the borides and carbides. Using transmission electron microscopy the morphology of the particles of the strengthening phase was studied. Maximum plasticity in the two-phase materials occurs in the range of small concentrations of the second phase (0.1–0.2 vol.%) that corresponds to the condition D g = Λ , where D g is the grain size and Λ is the mean free path between particles. The experimental values obtained for the yield stress were compared with the values calculated on the basis of the dislocation models of Orowan and Ansell-Lenel. We found that the qualitative agreement between the two using the Ansell-Lenel equation is purely of a formal nature. We also found that it is necessary to take into account the contribution from the particle-matrix interface when considering the yield strength of these two-phase materials.