Mo Zr Research Articles

The AES investigation for MoZr alloy surface composition

A MoZr alloy having 3 at% Zr and 0.05 at% of C has been investigated by Auger electron spectroscopy (AES) methods. The results under investigation demonstrate a complicated trend in temperature dependence of the element surface composition in the interval from room temperature up to 2150 K. The level of carbon and oxygen impurity concentrations has been obtained at temperatures between approximately 1400 K and 50 K. As a result of the Kirkendall effect the Zr content is 5 times larger than that of the room temperature due to strong Zr atom diffusion onto the alloy surface. The emissive features of the alloy-oxygen-cesium are dependent upon not only the constituents but upon the carbon concentration either by which the boundary value of approximately 1.2 eV for the work function can not be reached. The presence of carbon atom impurities on the alloy surface may result in possible carbide formation thus precluding homogeneous Zr single - atom film to be formed on the alloy surface as well as metal-oxygen-cesium system film.

Effect of sputtered Co–Mo–Zr amorphous underlayer on the c-axis dispersion of sputtered Co–Cr films

Crystallographic orientations of Co–Cr films on Co–Mo–Zr amorphous underlayers, the morphology and the surface state of the Co–Mo–Zr film were investigated. The morphology of Co–Mo–Zr film depends on the substrate temperature and sputtering modes for deposition. When the effective substrate temperature is higher than a critical temperature (225 °C), the surface is smooth and columnar structure disappears, and the c-axis dispersion (Δθ50) of Co–Cr film on this underlayer becomes small. Flat surface of Co–Mo–Zr film is one of the essential conditions for small c-axis dispersion of Co–Cr film. Effects of surface contamination are also examined. Carbon is effective to lower the surface energy and to improve the c-axis orientation of Co–Cr film.

Effect of thermomechanical processing on superplasticity in Ti–Al–Mo–Zr alloy

Superplasticity in terms of total tensile elongation was studied in a titanium alloy of nominal composition Ti–6·5Al–3·3Mo–1·6Zr (wt-%) for three strain rates (1·04 × 10−3, 2·1 × 10−3, and 4·2 × 10−3s−1) and in the temperature range 1123–1223 K for microstructures obtained by different processing schedules. Fine equiaxed microstructure with a low aspect ratio of 1·15 was accomplished in this alloy by combining two types of deformation. While the first step consists of heavy deformations for refining and intermixing the phases, a second step, consisting of light homogeneous reductions in several stages, was necessary to remove the banding that developed during the first step. The resulting microstructure underwent enormous tensile elongation (1700–1725%), even under relatively high strain rates (1·04 × 10−3 and 2·1 × 10−3s−1), making this alloy most suitable for commercial superplastic forming. The present investigation also revealed that the usual sheet rolling practice of heavy reductions to refine the microstructure leads to localised banding which could not be removed by annealing; therefore, the tensile elongation was limited to 770% only. The reason for this may be attributed to the resistance in grain boundary sliding and rotation encountered in microstructures with shear bands and grains with high aspect ratio. Strain enhanced grain growth was also greater in these microstructures.MST/555

Effect of thermomechanical processing on superplasticity in Ti–Al–Mo–Zr alloy

AbstractSuperplasticity in terms of total tensile elongation was studied in a titanium alloy of nominal composition Ti–6·5Al–3·3Mo–1·6Zr (wt-%) for three strain rates (1·04 × 10−3, 2·1 × 10−3, and 4·2 × 10−3s−1) and in the temperature range 1123–1223 K for microstructures obtained by different processing schedules. Fine equiaxed microstructure with a low aspect ratio of 1·15 was accomplished in this alloy by combining two types of deformation. While the first step consists of heavy deformations for refining and intermixing the phases, a second step, consisting of light homogeneous reductions in several stages, was necessary to remove the banding that developed during the first step. The resulting microstructure underwent enormous tensile elongation (1700–1725%), even under relatively high strain rates (1·04 × 10−3 and 2·1 × 10−3s−1), making this alloy most suitable for commercial superplastic forming. The present investigation also revealed that the usual sheet rolling practice of heavy reductions to refi...

Age-hardening response in rapidly quenched molybdenum alloys

Two molybdenum-rich alloys, MoB and MoZr1B, were processed into ribbons and foils by arc melt-spinning and the hammer-and-anvil technique. Strong grain refinement and solution strengthening were observed in the as-quenched materials. On heat treatment, a strong age-hardening response was evident in these alloys. The precipitates responsible for age hardening were identified as Mo 2B in MoB alloys and Mo 2B and ZrB 2 in Mo4Zr1B alloy.

Catalytic activity and structure of Mo oxide highly dispersed on ZrO2 for oxidation reactions

The structure of Mo–Zr oxides has been investigated by X-ray diffraction and Fourier-transform infrared and laser Raman spectra. At low Mo content, MoO3 is highly dispersed on ZrO2, an amorphous phase being formed which is characterized as polymolybdates. The i.r. and Raman bands due to MoO in polymolybdate are shifted from 930 to 970 cm–1 with increasing Mo content on ZrO2, suggesting that with low Mo catalysts surface Mo species are more distorted. The rates of oxidation of ethanol and propene pass through maxima around 10 atom % Mo. These results provide evidence that the rates over polymolybdate are 10–20 times higher than those over crystalline MoO3.

Shell model calculations for the Mo(d,Li6)Zr reaction

Shell model calculations were performed to obtain spectroscopic factors from microscopic wave functions of nuclei which were studied with the (d, /sup 6/Li) reaction in the A = 90 mass region. Though experimental level schemes for Zr, Nb, and Mo isotopes are reproduced rather well by the calculations, relative strengths measured for the Mo(d, /sup 6/Li)Zr reaction are less well explained.

High corrosion resistance of amorphous CoCrMoZr alloys

High corrosion resistance of amorphous CoCrMoZr alloys

Superconductivity and NMR investigations of amorphous BeNbZr and BeMoZr alloys

9Be NMR investigations and measurements of the superconducting properties and the resistivity are reported for amorphous Be 32.5Nb xZr 67.5−x and Be 32.5Mo xZr 67.5−x alloys (x = 2.5; 5; 7). Line width analysis suggests an enlarged Nb concentration around the Be sites for the BeNbZr alloys. Comparing the two types of alloys the Knight shifts are of the same order of magnitude whereas the T c and B c2(0) values are slightly smaller than for the Nb alloys. For Be-Nb-Zr T c and K increases with the Nb content. The results are discussed in connection with the density of states N(E F).