Preparation of diamond/aluminum composite with titanium coating on diamond powder by microwave technology

In this research, the diamond particles were coated with titanium by microwave heating method, then the Ti-coated diamond particles were used as raw material to fabricate the diamond/Al composites by microwave sintering. The result shows that the diamond particles could be covered with a uniform and continuous Ti coating under microwave irradiation, and the best Ti coating was obtained at 810 °C for 1 h. The metallic bond between diamond and Ti was formed to generate the intermediate transition layer of TiC. The diamond/Al composites which used Ti-coated diamond particles as raw material and were fabricated by microwave sintering show high relative density and hardness. The relative density and hardness of the diamond/Al composites increased with the temperature. While the composites were sintered at 710 °C for 1 h, the density could reach 2.855 g·cm−3, and relative density was 92.09%, which shows better microstructures and properties. There is Al3Ti alloy phase in Ti-coated diamond/Al composites, so the Ti-coated diamond can be well combined with the Al matrix, which can further improve the properties of the composites.

Selective Laser Melting of High Relative Density and High Strength Parts Made of Minor Surface Oxidation Treated Pure Copper Powder

Pure Copper (Cu) is very difficult to prepare using selective laser melting (SLM) technology. This work successfully prepared the pure Cu with high relative density and high strength by the SLM technology using a surface oxidation treatment. The gas-atomized pure Cu powder was used as the feedstock in this work. Before the SLM process, the pure Cu powder was initially handled using the surface oxidation treatment to coat the powder with an extremely thin layer of Cu2O. The SLMed highly dense specimens contain α-Cu and nano-Cu2O phases. A relationship between the processing parameters (laser power (LP), scanning speed (SS), and hatch space (HS)) and density of Cu alloy in SLM was also investigated. The microstructure of SLMed Cu consists of fine grains with grain sizes ranging from 0.5 to ~30 μm. Tensile testing and detailed microstructural characterization were performed on specimens in the as-SLMed and pure copper state specimens. The mechanical property experiments showed that the specimens prepared by SLM technology containing nano-oxide phases had higher yield strength and tensile strength than that of other SLM-built pure copper. However, the elongation was remarkably decreased compared to other SLM-built pure copper, due to the fine grains and the nano-oxides.

Effects of B2O3 doping on the dielectric and piezoelectric properties of (K,Na,Li)NbO3-BaZrO3-(Bi,Na)TiO3 ceramics

(K,Na,Li)NbO3-BaZrO3-(Bi,Na)TiO3-x B2O3 (abbreviated as KNLN-BZ-BNT-x B2O3) ceramics were prepared by conventional solid state reaction method. The effects of B2O3 content on dielectric and piezoelectric properties of the KNLN-BZ-BNT ceramics have been studied. Based on the identification by X-ray diffraction (XRD), all the samples show a two-phase coexistence zone consisting of rhombohedral (R) and tetragonal (T) phases. For the ceramics with x = 0.5 wt%, the sintering temperature was observed to reduce from 1200 oC to 940 oC, while the samples maintained a high relative density around 97%. Because of the high densification and large grain size, the dielectric and piezoelectric properties were improved. As a result, the ceramics with x = 0.5 wt% sintered at 940 oC exhibited good properties of d 33 = 197 pC/N, k p= 0.29, tan δ = 0.029 and ε r = 1889, together with a Curie temperature (T C) of 222 oC.

TYPES PRODUCTIVITY IN CONDITION OF THE SOUTH URAL TAIGA SUBZONE

По данным материалов 10 постоянных пробных площадей (ППП) рассмотрены лесоводственно- таксационные показатели древостоев сосняков ягодникового типа леса, пройденных выборочными руб- ками (первый приём равномерно-постепенной рубки). Все ППП были заложены на территории Ураль- ского учебно-опытного лесхоза. Изучаемые древостои характеризуются высокой относительной пол- нотой до рубки (0,76–1,0), I–III классами бонитета в возрасте 110–130 лет и высокой густотой. Запас стволовой древесины варьируется до рубки от 323,0 до 619,0 м3/га, что указывает на высокую эксплуа- тационную ценность сосновых насаждений ягодникового типа леса. Преобладающей породой в составе всех пробных площадей является сосна. Встречаются и другие хвойные породы – ель, пихта и листвен- ница. Доля участия в составе последних сильно варьирует. Из лиственных пород доминирует береза. Также в состав лиственных пород входят липа и осина, на их долю приходится не более одной единицы состава. Формула состава древостоя существенно не изменилась через 4 года после рубки, сосна оста- лась преобладающей породой. Средний показатель диаметра увеличился на 2,3 см, высоты – на 1,3 м. Густота в среднем сократилась на 193 дерева/га. Запас деревьев сосны снизился на 148 м3/га, запас сухо- стойных деревьев – на 2 м3/га. Проведенные исследования доказывают, что при вырубке в первый прием равномерно-постепенной рубки в условиях сосняка ягодникового удаляются сухостойные, отставшие в росте, фаутные деревья и деревья 4 и 5 класса роста по Крафту. Отмечается положительное изменение лесоводственно-таксационных показателей насаждений. В частности, улучшаются их эстетические ха- рактеристики и антропогенная привлекательность, а также рубки способствуют повышению продуктив- ности и производительности насаждений. According to the materials of 10 permanent sample plots (PPP), silvicultural and taxation indicators of forest stands of berry-type pine forests passed by selective felling were considered (the fi rst method of uniformly gradual felling). All permanent test plots were laid on the territory of the Ural training and experimental forestry enterprise. The studied stands are characterized by a high relative density before felling (0,76–1,0), I–III quality classes at the age of 110–130 years and high density. The stock of stem wood varies before felling from 323,0 to 619,0 m3/ha, which indicates a high operational value of pine plantations of berry forest type. Pine is the predominant species in all sample plots. There are also other conifers – spruce, fi r and larch. The share of participation in the composition of the latter varies greatly. The dominant deciduous species is birch. Also, the composition of deciduous species includes linden and aspen, they account for no more than one unit of composition. The formula of the stand composition did not change signifi cantly 4 years after logging, pine remained the predominant species. The average diameter increased by 2,3 cm, height by 1,3 m. The average density decreased by 193 trees/ha. The stock of pine trees decreased by 148 m3/ha, the stock of dry trees by 2 m3/ha. The conducted studies prove that when cutting down in the fi rst step of evenly-gradual felling in the conditions of a berry-type pine forest, the queue of dry, stunted, faut trees and trees of the 4th and 5th growth class according to Craft contributes to a positive change in the forestry and taxation indicators of plantings, this improves their aesthetic and anthropogenic attractiveness, and also contributes to increasing the productivity and productivity of such plantings.

Microstructure and Mechanical Properties of High Relative Density γ-TiAl Alloy Using Irregular Pre-Alloyed Powder

Preparing high relative density γ-TiAl alloy by pressure-less sintering at low-cost has always been a challenge. Therefore, a new kind of non-spherical pre-alloyed TiAl powder was prepared by the reaction of TiH2 powder and Al powder at 800 °C to fabricate high-density Ti-48Al alloy via pressure-less sintering. The oxygen content was controlled to below 1800 ppm by using coarse Al powder (~120 μm). The sintered densities ranged from 92.1% to 97.5% with sintering temperature varying from 1300 °C to 1450 °C. The microstructure of the sintered compact was greatly influenced by the sintering temperature. The as-sintered samples had a near-γ structure at 1350 °C, a duplex structure at 1400 °C, and a nearly lamellar structure at 1450 °C. To achieve full densification, non-capsule hot isostatic pressing was performed on the 1350 °C and 1400 °C sintered samples. As a result, high compressive strengths of 2241 MPa and 1931MPa were obtained, which were higher than the existing Ti-48Al alloys.

Self-passivating smart tungsten alloys for DEMO: a progress in joining and upscale for a first wall mockup

Self-passivating, so-called smart alloys are under development for a future fusion power plant. These alloys containing tungsten, chromium and yttrium must possess an acceptable plasma performance during a regular plasma operation of a power plant and demonstrate the suppression of non-desirable oxidation of tungsten in case of an accident. The up-scaling of the bulk smart alloys to the reactor-relevant sizes has begun and the first samples with a diameter of 50 mm and thickness of 5 mm became available. The samples feature high relative density of above 99% and good homogeneity. With production of bulk samples, the research program on joining the smart alloy to the structural material was initiated. In a present study, the novel titanium–zirconium–beryllium braze was applied successfully to join the smart alloy to the Rusfer-reduced-activation steel. The braze has survived at least a hundred of cyclic thermal excursions in the range of 300–600 °C without mechanical destruction.

Fabrication of Integrated Ni-Ti Alloys Possessing Both Super-elastic and Shape Memory Properties by Laser Powder Bed Fusion

Purpose: Integrated Ni-Ti alloys possessing both super-elastic (SE) properties and shape memory effects (SMEs) greatly increase the flexibility of designing complex systems and have broad application prospects. However, existing research mainly focuses on connecting ready-made SE parts and SME parts though welding. Method: In this paper, laser powder bed fusion (LPBF) was used to fabricate integrated Ni-Ti alloys. First, SE parts with high relative density were fabricated with a Ni-rich powder. Then, different process parameters were used to fabricate the SME parts with a Ti-rich powder based on the SE parts. The integrated component with the best mechanical properties herein was selected. Metallographic analysis, energy dispersive X-ray spectroscopy, differential scanning calorimetry and micro-hardness analyses were carried out for this sample. Findings: The results show that the integrated component possessed both SE and SME properties at room temperature. Moreover, at the junction of the two materials, the grains were continuous and complete, which indicates that the joint had good quality. Originality: Our work confirms that LPBF is a feasible method to fabricate integrated Ni-Ti alloys possessing both SE and SME properties.

Mapping Spatial Distribution of Pores in an Additively Manufactured Gold Alloy Using Neutron Microtomography

A crucial criterion for the quality of the additively manufactured parts is the porosity content for achieving an acceptable final relative density. In addition, for jewelry applications, visible pores are unacceptable at or in the vicinity of the surface. In this study, non-destructive 3D neutron microtomography is applied to map the spatial distribution of pores in additively manufactured red-gold samples. The 3D imaging assessment underlines the high relative density of the printed red-gold sample and indicates residual pore sizes are predominantly below the limit of concern for jewelry applications. The 3D maps of pores within printed samples highlight the effect of the scanning strategy on the final quality and location of pores in the printed samples. These results confirm that neutron microtomography is a novel and precise tool to characterize residual porosity in additively manufactured gold alloys and other higher-Z materials where such investigation using other non-destructive methods (such as X-rays) is challenging due to the limited penetration depth.