Papers by Keyword: Alloy

Abstract: In aerospace industry, chromic acid anodizing (CAA) has been traditionally used as a non-destructive testing (NDT) technique to detect flaws in aluminium alloys. However, with the increasing restriction on the use of chromic acid and the application of lithium-containing aluminium alloys to aircraft structures, the capability of anodizing as a NDT method is challenged. In this work, machining damage was deliberately introduced to an Al-Li-Cu alloy AA2099-T8. Then, the visibility of the machine damage after tartaric-sulphuric acid anodizing (TSAA), which is an environmentally friendly anodizing process, was studied. It is suggested that, with proper lighting condition, it is possible to replace CAA with TSAA for detecting machining damage on lithium-containing aluminium alloys during manufacturing.

Abstract: Positron annihilation Doppler broadening spectroscopy (DBS) has been used for the detection of structural defects in Fe-9wt%Cr (Fe-9Cr) alloy in the as-prepared and implanted states. Defects were created by He and H ion implantation with a kinetic energy of 250 keV. DBS is a non-destructive method and is a unique tool for the observation of open volume defects like vacancies and vacancy clusters in solids. A positron beam with variable positron energy was used for the measurement of defect depth profiles up to 1.5 µm. The obtained results provide qualitative and semi-quantitative information about radiation induced defects and their chemical environment. Although the collision damage from helium implantation was one order of magnitude higher than for the case of hydrogen, the changes in S and W parameters are much less significant, probably due to considerably lower mobility of helium in the implanted materials, which results in helium capture by the created open volume defects.

Abstract: Rheological properties of semi-solid alloys are closely knit to the solid-phase microstructure. Parameters such as particle size distribution are commonly determined by 2D cross section analysis. The determination of mechanisms such as particle deagglomeration with increasing shear rate however, requires information on the 3D spatial distribution. By means of synchrotron radiation tomography and SEM on AlCu samples, particle size distributions and the not yet microscopically observed interrelation of shear rate and particle agglomeration in thixo-material is investigated.

Abstract: The largest proportion of element in master alloys were iron and pure iron smelting industrial used accounts for 70% of the total raw materials. Iron produced by secondary refining has the highest purity. If the inclusion in the raw materials is very low, inclusions in smelting amorphous master alloy would be lower. The carbon content of 0.1% in the carbon-75 ferrosilicon, but ferrosilicon dosage is small, generally is about 10%, so the carbon content in the master alloy is below 0.01%. Boron anhydride generally containing boron oxide at about 95%, the rest is mainly water, contains less impurities, the alumina content is generally below 0.1%, as well as chloride, which have little effect on master alloy smelting. Impurities in additive calcium oxide, calcium fluoride are generally below 10%, mainly are oxides, presenting in the slag in the smelting master alloys basically.

Abstract: Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, particularly where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers. In this paper, we fabricated metallic glass of Nd-based and carried out experimental research. This kind of metallic glass has shown a distinct glass transition and stable super-cooled liquid region. At the same time, we find the paramagnetic performance of Nd-based metallic glass is different from other hard magnetic alloys at ordinary temperature. The DSC experiment indicate that the glass transition temperature increase with the heating temperature.

Abstract: The lifetime of drilling tools for petroleum well perforation is strongly affected by the type of insert at the crown of the tool. Usually, this insert is made a of hardmetal (WC-Co) cermet with embedded diamond particles. In the present work an investigation on the effect of Cu and Ti as doping agents on a WC-6%Co cermet was conducted. I was found a change in coercive force in the interval 12 to 34 kJ/m and harness from 73 to 89 HRA with improving adhesion. It was also shown that this could significantly increase the operational capacity of a drilling tool.

Abstract: In the production of metallic saw blades segments impregnated with diamond particles, there are two basic functions of the metal-based matrix. First, to hold tightly the particles and, second, to display wear rate compatible with the diamond loss. The most common matrix materials are composed of either cobalt or iron, nickel, copper, bronze alloys and tungsten alloys. This paper investigated the microstructure and mechanical properties of Ni-Fe-Cu-Sn alloys as the metallic matrix of saw blade segments. It was found that the Ni content significantly influences the microstructure and mechanical properties of the alloy. Information on the diamond bonding efficiency of the Ni-Fe-Cu-Sn alloy as a cutting tool matrix were disclosed.

Abstract: The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed Al-Mn-Si alloy was investigated through TEM observations, anodization metallography, tensile tests and Tafel polarization analysis. High density precipitates were found in the Zn-containing alloys and the alloy with 1.5 % Zn had the most uniform precipitation. The Zn element could restrain recrystallization of the alloy. Tensile test results indicated that Zn has a great effect on tensile strength of Al-Mn-Si alloy. The alloy with 1.8 % Zn addition had the highest ultimate tensile strength. The electrochemical testing results indicated that Zn element had great impact on the corrosion potential of the as-annealed alloys tested in 0.5% NaCl solutions. Alloying with Zn element could make the corrosion potential shift to negative direction but increase the resistance to pitting corrosion

Abstract: The porous nanocrystalline Fe0.2(Co20Ni80)0.8 alloy microfibers with diameters of 2-4 μm have been prepared by the citrate-gel and phase transformation process. The sound absorption coefficient for microfibers samples is measured by the standing wave tube method and it is is over 0.8 for the 15 mm thick sample at the frequency range of 2300-6000 Hz, which is extended to 600-6300 Hz for the 40 mm thick sample. The band width with the sound absorption coefficient above 0.6 is wider than 4300 Hz for the 15 mm thick sample and 5800 Hz for the 40 mm thick sample. For the 40 mm thick sample, the maximum absorption coefficient, noise absorption coefficient, noise reduction coefficient and half-width of the absorption peak are 0.99, 0.59, 0.64 and 5828 Hz, respectively. These microfibers are promising advanced acoustic absorbers.

Abstract: Due to the low density and high specific strength, magnesium and its alloys have been extensively used in the automobile and aerospace applications, where the weight reduction is critical. However, they are highly prone to corrosion, which has greatly limited their application in the automotive and aerospace industries. This paper briefly reviews the technologies for improving the corrosion and wear resistance of magnesium alloys and finds that the widespread application of magnesium alloys is still limited by the lack of proper protective coatings. Therefore, there is still a need to explore new materials and methods for the effective protection of magnesium and its alloys.