The strengthening effect of inter-layer cold working and post-deposition heat treatment on the additively manufactured Al-6.3Cu alloy

Wire + Arc Additive Manufacture (WAAM) attracts great interest from the aerospace industry for producing components with aluminum alloys, particularly Al-Cu alloy of the 2000 series such as 2219 alloy. However the application is restricted by the low strength properties of the as-deposited WAAM metal. In this study two strengthening methods were investigated - inter-layer cold working and post-deposition heat treatment. Straight wall samples were prepared with 2319 aluminum alloy wire. Inter-layer rolling with loads of 15 kN, 30 kN and 45 kN were employed during deposition. The ultimate tensile strength (UTS) and yield strength (YS) of the inter-layer rolled alloy with 45 kN load can achieve 314. MPa and 244. MPa respectively. The influence of post-deposition T6 heat treatment was investigated on the WAAM alloy with or without rolling. Compared with inter-layer rolling, post-deposition heat treatment can provide much greater enhancement of the strength. After T6 treatment, the UTS and YS of both of the as-deposited and 45 kN rolled alloys exceeded 450. MPa and 305. MPa respectively, which are higher than the properties of the wrought 2219-T6 alloy. The strengthening mechanisms of this additively manufactured Al-6.3Cu alloy were investigated through microstructure analysis

Enhanced Thermoelectric Performance of c-Axis-Oriented Epitaxial Ba-Doped BiCuSeO Thin Films

Abstract We reported the epitaxial growth of c-axis-oriented Bi1−x Ba x CuSeO (0 ≤ x ≤ 10%) thin films and investigated the effect of Ba doping on the structure, valence state of elements, and thermoelectric properties of the films. X-ray photoelectron spectroscopy analysis reveal that Bi3+ is partially reduced to the lower valence state after Ba doping, while Cu and Se ions still exist as + 1 and − 2 valence state, respectively. As the Ba doping content increases, both resistivity and Seebeck coefficient decrease because of the increased hole carrier concentration. A large power factor, as high as 1.24 mWm−1 K−2 at 673 K, has been achieved in the 7.5% Ba-doped BiCuSeO thin film, which is 1.5 times higher than those reported for the corresponding bulk samples. Considering that the nanoscale-thick Ba-doped films should have a very low thermal conductivity, high ZT can be expected in the films

Estimating the Effects of Deficit Irrigation on Water Absorption and Utilization of Tomatoes Grown in Greenhouse with Hydrus-1D Model

Quantitative analysis of tomato root water uptake and soil water utilization in the root zone under deficit irrigation is an important tool to improve agricultural water utilization efficiency. In this study, three different deficit irrigation levels were set at the flowering and fruit development stage (Stage I) and the fruit-ripening stage (Stage II), respectively. The Hydrus-1D model and field data were used to analyze the effects of deficit irrigation on tomato root growth, soil water uptake and utilization in the root zone. The results showed that deficit irrigation could reduce the total root length density of water-absorbed roots but increase the water-absorbed root length density of the underlying soil (30–60 cm). Moderate and severe water deficits at Stage II increased the water-absorbed root length density of the underlying soil by 0.10–6.26% and 2.12–11.71% compared with a mild water deficit. Considering tomato root growth, the Hydrus-1D model can improve the accuracy of soil moisture simulation. The main water absorption zone of tomato roots was 0–30 cm. Compared with full irrigation, the ratio of water absorption by the underlying root system (30–60 cm) to the total water absorption of the profile (0–60 cm) increased by 2.16–2.82% and 5.34–6.34% due to mild and moderate water deficits at Stage I. At Stage I and Stage II, a water deficit could reduce soil evaporation. T3 had the highest water use efficiency in two years, which was 24.07% (T9) and 20.47% (T8) higher than the lowest value, respectively. The optimal deficit irrigation scheme under this experiment condition is as follows: the soil water content was 70–90% θf (field capacity) at Stage I and was 40–60% θf at Stage II (T3)

Effects of Welding Heat Input on Microstructure and Electrochemical Behavior of Flux-Cored Arc-Welded Q690 HSLA Steel

In this work, the weld metal (WM) for the Q690 high-strength low-alloy (HSLA) steel was prepared through flux-cored arc welding (FCAW) at 10 kJ/cm and 20 kJ/cm heat inputs. The effect of welding heat input on the relationship between the microstructural factors and the electrochemical behavior of the FCAW Q690 steel was studied. Due to the fine grain and acicular ferrite affected by the 10 kJ/cm low heat input, the WM presented similar electrochemical behavior to the Q690 base metal, which would minimize the risk of galvanic corrosion. Also, at 20 kJ/cm of high welding heat input, the WM with higher-sized bainite structure was prone to galvanic corrosion risk minimization

Types, characteristics, and implications on the exploration of far-source oil reservoirs in the north Melut Basin

The Melut Basin is an important petroliferous basin in African Continent. The northern part of the basin is characterized by far-source oil accumulation with the oil generation in the Lower Cretaceous and the oil accumulation in the Paleogene. Clarifying the formation conditions and controlling factors of the far-source oil accumulations is the key to improve the exploration success rate and seek new potential areas of far-source oil accumulations in the Melut Basin. Based on the study of regional petroleum geological conditions and the analysis of key oil accumulations, the formation conditions, types, characteristics and potential exploration areas of far-source oil accumulations in the Melut Basin have been systematically studied. The results show, ①The north Melut Basin develops two types of far-source oil accumulations with different hydrocarbon charging patterns and accumulation modes in the Paleogene Yabus Formation, the far-source fault-lithology combination oil accumulations within the oil kitchen and the far-source fault-block oil accumulations outside the oil kitchen; ②The formation of far-source oil accumulations of the Yabus Formation inside oil kitchen depends on the coupling of three geological conditions, that is, the "two strong and one weak" three-stage rifting cycles, creating conditions for the formation of the Paleogene Yabus-Adar far-source reservoir-caprock combination; the development of oil-rich sag, providing necessary oil supply for the Yabus far-source traps; and the multi-stage rifting activities, providing vertical migration pathways for hydrocarbon charging in the Yabus far-source traps; ③The far-source oil accumulations inside oil kitchen are mainly charged by the vertical hydrocarbon infilling through the oil-source faults, and the oil-source faults are the main controlling factor for the hydrocarbon accumulation. The identification of oil-source faults and the evaluation of the lateral sealing capability of trap-controlling faults are the key elements for the far-source fault-block traps inside oil kitchen; ④The far-source oil accumulations outside oil kitchen are mainly charged by lateral hydrocarbon infilling from the oil-rich sag. The transportation ridges formed by sand-rich strata, fault blocks and paleo-uplifts control the hydrocarbon accumulation of far-source traps outside oil kitchen. The identification of transportation ridges and the study on the hydrocarbon charging extent are the main evaluation focus of far-source traps outside oil kitchen. The research results successfully guided the exploration deployment and in-depth exploration of far-source oil accumulations in the Melut Basin, and have a great implication on the exploration of far-source oil accumulations in the other petroliferous basins

Effect of Rare-Earth Elements on the Corrosion Resistance of Flux-Cored Arc-Welded Metal with 10CrNi3MoV Steel

We modified the content of rare-earth elements (REE) in the flux-cored wire used to produce welds of high-strength low-alloy (HSLA) steel. The effect of REE addition on the microstructure as well as on the mechanical and electrochemical properties of the welded metal (WM) was investigated. REE-modified welded metals show very different responses during electrochemical impedance spectroscopy and the potentiodynamic polarization tests. The results indicate that the addition of REE of 0.3 wt.% facilitates a more uniform microstructure and improves both mechanical properties and corrosion resistance in welded metals

Metal-free oxidation of secondary benzylic alcohols using aqueous TBHP

<p>We report a simple, yet efficient metal-free oxidation of secondary benzylic alcohols in the presence of t-butyl hydroperoxide (70% TBHP) with high yields of up to 98%. This type of reaction can be carried out using a wide variety of substrates, requires no other organic solvent, and proves to be tolerant toward a variety of different functional groups.</p