Explore the vast range of titles available.

The mechanical behavior of titanium alloys has been mostly studied in quasi-static conditions when the strain rate does not exceed 10 s−1, while the studies performed in dynamic settings specifically for Ti-based composites are limited. Such data are critical to prevent the “strength margin” approach, which is used to assure the part performance under dynamic conditions in the absence of relevant data. The purpose of this study was to obtain data on the mechanical behavior of Ti-based composites under dynamic condition. The Metal Matrix Composites (MMC) on the base of the alloy Ti-6Al-4V (wt.%) were made using Blended Elemental Powder Metallurgy with different amounts of reinforcing particles: 5, 10, and 20% of TiC or 5, 10% (vol.) of TiB. Composites were studied at high strain rate compression ~1–3 × 103·s−1 using the split Hopkinson pressure bar. Mechanical behavior was analyzed considering strain rate, phase composition, microstructure, and strain energy (SE). It is shown that for the strain rates up to 1920 s−1, the strength and SE of MMC with 5% TiC are substantially higher compared to particles free alloy. The particles TiC localize the plastic deformation at the micro level, and fracturing occurs mainly by crushing particles and their aggregates. TiB MMCs have a finer grain structure and different mechanical behavior. MMC with 5 and 10% TiB do not break down at strain rates up to almost 3000 s−1; and 10% MMC surpasses other materials in the SE at strain rates exceeding 2200 s−1. The deformation mechanism of MMCs was evaluated.

The objective of this work was to characterize the Al x Cu y intermetallic compounds (IMCs) formed at the abutting interface during solid-state friction-stir welding (FSW) of 6082 aluminum alloy and pure copper. As IMCs are potential sources of flaws in case of mechanical loading of welds, their study is essential at various scale lengths. In the present case, they have been identified by neutron diffraction, electron backscattered diffraction, and transmission electron microscopy. Neutron diffraction analyses have shown that a shift of the tool from the interface, in particular towards the Cu part, generates an increase of the IMCs’ volume fraction. In accordance with an exacerbation of its kinetics of formation by FSW, a 4- μ m-thick layer has precipitated at the interface despite the shortness of the thermal cycle. This layer is composed of two sublayers with the Al 4 Cu 9 and Al 2 Cu stoichiometry, respectively. Convergent beam electron diffraction analyses have, however, disclosed that the crystallography of the current Al 2 Cu compound does not comply with the usual tetragonal symmetry of this phase. The Al 2 Cu phase formation results from both the local chemical composition and thermodynamics, whereas the development of Al 4 Cu 9 is rather due to both the local chemical composition and the shortness of the local FSW thermal cycle.

Interest in power systems economics is gaining momentum with the recent power supply shortages in America and the rising cost of fossil fuels.The involvement of independent power generators, brokers and distributors has changed the way in which power systems operate.

The structure and phase evolution of nanocrystalline Ce^sub 1- x^Ln^sub x^O^sub 2- x/2-[delta]^ (Ln = Yb, Lu, x = 0 - 1) oxides upon heating in H^sub 2^ was studied for the first time. Up to 950 °C the samples were single-phase, with structure changing smoothly with x from fluorite type (F) to bixbyite type (C). For the Lu-doped samples heated at 1100 °C in the air and H^sub 2^, phase separation into coexisting F- and C-type structures was observed for ~0.40 < x < ~0.70 and ~0.25 < x < ~0.70, respectively. It was found also that addition of Lu^sup 3+^ and Yb^sup 3+^ strongly hinders the crystallite growth of ceria during heat treatment at 800 and 950 °C in both atmospheres. Valency of Ce and Yb in Ce^sub 0.1^Lu^sub 0.9^O^sub 1.55-[delta]^ and Ce^sub 0.95^Yb^sub 0.05^O^sub 1.975-[delta]^ samples heated at 1100 °C was studied by XANES and magnetic measurements. In the former Ce was dominated by Ce^sup 4+^, with small contribution of Ce^sup 3+^ after heating in H^sub 2^. In the latter, Yb existed exclusively as 3+ in both O^sub 2^ and H^sub 2^.[PUBLICATION ABSTRACT]

The structure and phase evolution of nanocrystalline Ce(1-x)Ln(x)O(2-x/2-delta) (Ln = Yb, Lu, x = 0 - 1) oxides upon heating in H(2) was studied for the first time. Up to 950 degrees C the samples were single-phase, with structure changing smoothly with x from fluorite type (F) to bixbyite type (C). For the Lu-doped samples heated at 1100 degrees C in the air and H(2), phase separation into coexisting F- and C-type structures was observed for ~0.40 < x < ~0.70 and ~0.25 < x < ~0.70, respectively. It was found also that addition of Lu(3+) and Yb(3+) strongly hinders the crystallite growth of ceria during heat treatment at 800 and 950 degrees C in both atmospheres. Valency of Ce and Yb in Ce(0.1)Lu(0.9)O(1.55-delta) and Ce(0.95)Yb(0.05)O(1.975-delta) samples heated at 1100 degrees C was studied by XANES and magnetic measurements. In the former Ce was dominated by Ce(4+), with small contribution of Ce(3+) after heating in H(2). In the latter, Yb existed exclusively as 3+ in both O(2) and H(2).

The structure and phase evolution of nanocrystalline Ce 1 − x Ln x O 2 − x /2 − δ (Ln = Yb, Lu, x  = 0 − 1) oxides upon heating in H 2 was studied for the first time. Up to 950 °C the samples were single-phase, with structure changing smoothly with x from fluorite type (F) to bixbyite type (C). For the Lu-doped samples heated at 1100 °C in the air and H 2 , phase separation into coexisting F- and C-type structures was observed for ~0.40 <  x  < ~0.70 and ~0.25 <  x  < ~0.70, respectively. It was found also that addition of Lu 3+ and Yb 3+ strongly hinders the crystallite growth of ceria during heat treatment at 800 and 950 °C in both atmospheres. Valency of Ce and Yb in Ce 0.1 Lu 0.9 O 1.55 − δ and Ce 0.95 Yb 0.05 O 1.975 − δ samples heated at 1100 °C was studied by XANES and magnetic measurements. In the former Ce was dominated by Ce 4+ , with small contribution of Ce 3+ after heating in H 2 . In the latter, Yb existed exclusively as 3+ in both O 2 and H 2 .