Papers by Keyword: Property

Abstract: Fe and Si elements can form non-dissolvable phases in Al-Zn-Mg-Cu alloys and furtherly affect the property of finished products while the influence of minor contents lacks sufficient investigations. In present work, 7085 alloy with different Fe and Si contents (named by LFS alloy, MFS alloy and HFS alloy as Fe and Si contents progressively enhanced) was investigated and corresponding microstructure and property during the whole fabrication were analyzed via OM, SEM and DSC observation and tensile property, fracture toughness and salty-spray corrosion property. The results showed that Fe-containing phase existed in as-cast microstructure of three alloys while part of Fe-containing phases of HFS alloy has Si element. After homogenization treatment, coarse eutectic phases had dissolved into the matrix while Fe-containing phase remained in the alloys. Similarly, Si element existed in some Fe-containing phases of HFS alloy. The order of area fraction of remaining Fe-containing phases for the three alloys was LFS alloy<MFS alloy<HFS alloy. After extrusion, Mg(Zn,Cu,Al)₂ phase and Fe-containing phase possessed the majority, the former one was eliminated by solution treatment while the latter one had no obvious change. Under an unified aging treatment, the strength, elongation and fracture toughness were degraded with the increase of Fe and Si contents. Besides, the salt-spray corrosion property of HFS alloy was significantly inferior to LFS alloy and MFS alloy. This gave rise to a reference for controlling Fe and Si impurity of 7085 alloy for considering overall performance.

Abstract: As the main process of carbide tool coating fabrication, cathodic arc ion plating plays an important role in modern industrial production. This paper introduces the influence of process parameter selection on the coating properties of tools by cathodic arc ion plating. The process parameters mainly include nitrogen partial pressure, negative bias pressure and arc current, and the coating properties are mainly characterized by deposition rate, phase composition, coating hardness and surface quality. It can optimize the selection of process parameters on modern industrial production.

Abstract: As the main-stream of the machining coating, nitrogen-based coatings have irreplaceable advantages, such as high hardness, high strength, and good oxidation resistance recently. This paper introduces common multiple nitrogen-based coatings which including TiAlN, CrAlN, TiAlSiN, CrAlSiN and CrTiAlN coatings for cemented carbide tools. The microstructure and property of coating is depended on its chemical composition. Generally, compounds of different structures are formed between the various elements of the coating, and these have different forms of existence and properties: titanium and chromium exist in nitrides (face-centered cubic structure), aluminium solubilizes in TiN/CrN, and amorphous Si₃N₄ can make difference in fine grain strengthening. The Al₂O₃ and SiO₂ can improve oxidation resistance.

Abstract: The paper presents studies aimed at producing a three-component alloy from the powders of cobalt, chromium and molybdenum (66 wt % Co, 28 wt % Cr, 6 wt % Mo), with a stable phase structure by selective laser melting. At the beginning of the work, the initial powders were graded on sieves with mesh sizes of 20-70 µm. The powder mixtures were obtained by mechanical mixing of various fraction powders and mechanical alloying in a planetary ball mill. The samples were produced using the VARISCAF-100MVS selective laser melting unit. The melting process of powder materials was completed in a chamber filled with inert gas argon after preliminary vacuum degassing. The microhardness analysis of the samples before and after the thermal treatment was completed. The results of phase composition studies, X-ray diffraction analysis, scanning electron microscopy are presented. Examination of the X-ray profiles of the samples proves that the obtained alloy mainly contains the epsilon-phase which improves the hardness and the wear resistance of the product.

Abstract: This paper introduces the principle of PACVD coating technology, technical characteristics, equipment composition and material characteristics of CrN+DLC. Taking H13 steel as the research object, its surface was treated with CrN+DLC. The microstructure, bonding state and hardness of the interface were studied by means of metallography, SEM, hardness and component distribution of the surface layer. The anti-crack ability and grade of DLC layer were analyzed by studying the shape of crack distribution with Rockwell hardness indentation, and the high quality layer with crack grade of HF1 was obtained. With the dual properties of diamond and graphite of DLC, it can make the die surface have lower friction coefficient, higher hardness, higher impact toughness, better solid lubrication performance and higher corrosion resistance. Surface DLC coating technology provides a new solution to improve the performance of the die.

Abstract: The effects of Mg/Si ratio on precipitation behaviour and properties of Al-Mg-Si alloys were studied by using electrochemical test, corrosion test and transmission electron microscope (TEM). The results show that with the increases of Mg/Si ratio from 0.9 to 1.1, the density of the β" decreases, and the mechanical properties decrease. When the ratio of Mg/Si increases from 1.0 to 1.1, the density y of β" does not increase significantly, but the continuous degree of the MgSi phase decreases significantly. The source of cracks originate from MgSi phase, which reduces the mechanical properties. When the Mg/Si ratio is 0.9, the alloy is in an over-Si state, which results in serious intergranular corrosion (IGC).

Abstract: The production process, microstructure, and mechanical properties of 15MnNbR pressure vessel steel were studied by optical microscopy, universal tensile testing, and low-temperature impact toughness testing. It was found that the microstructure obtained after controlled rolling and cooling (known as thermo-mechanical control processing) consisted of ferrite and pearlite with non-uniform grain size. The banded microstructure was prominent, the strength was high, and the toughness was poor. After normalizing, the grain size was refined, both the microstructural uniformity and the banded microstructure were improved, and the strength and toughness of the steel were enhanced. After normalizing and water cooling, the grain was further refined, the microstructure was homogenized, the banded microstructure disappeared, and the strength and toughness of the test steel were improved simultaneously, resulting in excellent comprehensive mechanical properties.

Abstract: Heat resistant cobalt-based alloys have found a specific niche in the present-day mechanical engineering due to their unique properties. To begin with, cobalt-based alloys are used as corrosion, heat and wear resistant materials intended for aggressive environments and operation at extreme temperatures, e.g. blades, nozzles, swirlers, rings and other elements of turbines and internal combustion engines. Traditional molding methods applied in the mechanical engineering fail to provide necessary operational and technological characteristics of aforementioned machine parts. Owing to selective laser melting it is possible to reduce a production time and manufacturing costs for machine elements with a complex physical configuration and generate an alloy with an extraordinary structure, which is not found in traditionally combined compounds. A structure of cobalt exists in two crystal modifications: a hexagonal close-packed epsilon phase, a low-temperature phase and a face-centered cubic lattice gamma phase, a high-temperature phase. The alloy hardness is directly related to an amount of a low-temperature phase. The laser melting shortens a laser beam impact time on a powder composition due to a higher power and laser travelling speed. A high value of heat conductivity seems to be the reason for rapid solidification and cooling, which, in their turn, increase a percent of an alpha-martensite phase in an alloy and improve the hardness and wear resistance of machine parts. The reported paper summarizes studies aimed at the development of a stable phase structure three-component alloy (Сo-66 mass % Cr-6 mass % Mo) based on the cobalt-chromium-molybdenum system and mixed up via selective laser melting.

Abstract: In this work, pulp/lyocell wet-laid paper sheets have been consolidated by hydroentanglement techniques. Scanning electron microscopy has been used to evaluate the structures of wet-laid paper sheets before and after hydroentanglement. Wet tensile strength along longitudinal (preferential) and transverse directions show the effect of hydroentanglement techniques on the mechanical properties of wet-laid paper sheets. In addition, the air permeability and water absorbency properties of materials have been evaluated. The results show that the structures of wet-laid paper sheets become fluffy and fiber entanglements increase after consolidation. The wet tensile strength values of wet-laid paper sheets at the longitudinal and transverse directions are increased by 109.0% and 78.7%, respectively after hydroentanglement. The air permeability and water absorbency of wet-laid paper sheets are increased by 957.6% and 137.0%.

Abstract: Friction stir welded lap joints of 5083 aluminum alloy plates with thickness of 2mm and T2 pure copper plates with thickness of 3mm were prepared, and the microstructures and properties of lap joints were investigated. The results showed that Al and Cu interdiffusion occurred at the interface of the lap joints, the grains in the stir zone of Al were refined and the microhardness increased sharply. The joint of Cu can be divided into four parts, including the nugget zone (NZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and base metal (BM). Using the optimum welding parameters (rotation speed of 900rpm and welding speed of 100mm/min), the lap joints were well formed. There were fewer welding defects and the average shear tensile force reached 3.155KN. Also, the ductile-brittle hybrid fracture occurred at the transitional zone of the advancing side of the Al plates. XRD results showed that intermetallic compounds (IMCS) mainly composed of Al₂Cu and AlCu₄ were produced in the interface of the lap joints during welding.