1,720,983 research outputs found
Modulated (spinodal) alloys: Fehim Findik
Full text linkIn this work, after defining spinodal reactions experimental investigation on spinodal decomposition are overviewed for the last five decades. Also, future developments in spinodal decomposition for modulated alloys are forecasted and criticized in an outlook
A Case Study on the Selection of Materials for Eye Lenses
No full textA case study on the selection of materials for eye lenses is reported by means of Ashby's materials selection diagrams. In this study, 6 polymer materials of PMMA, PC, PS, PVC, PET, and PA are reviewed and their properties are found from the selection diagrams of Ashby and compared in a table. The final results confirmed that PMMA (acrylic) is the best material for eye lenses. The outcome also showed that the present material is environmental friendly being nontoxic and recyclable.</jats:p
Laser cladding and applications
Full text linkLaser coating is a material placement technique wherein a powder material is melted using a laser to coat a portion of a substrate. In this study, laser cladding and its applications are reviewed. First, background of the technique and its important parameters are highlighted. Then, control of laser cladding procedure is criticized. As an example of the process, laser cladding of titanium alloys is investigated. Finally, applications of laser cladding on gas turbine engines, dies and drilling spindles, tools, turbine blades are highlighted
Review of high temperature materials
Full text linkHigh-temperature materials play a significant role in sustainable engineering across various industries and applications. Sustainable engineering aims to design, develop, and implement solutions that minimize environmental impact, enhance resource efficiency, and promote long-term sustainability. The availability of substances that can be used efficiently at high temperatures allows pushing the limits of possible measurable demands. These substances include ceramics, polymers and metals. It is used in elevated temperature materials, aircraft and space structures, and space exploration. In this study, high temperature metals are classified including superalloys, platinum and refractory metals, refractory metals such as W, Nb, Mo, Ta. Also, ceramic materials are high temperature materials. Ceramics are criticized to use in elevated temperature due to their high hardness, extraordinary strength in compression, excellent thermal stability, short-term thermal extension and tremendously great melting temperature. Ceramics that encounter these standards are carbides and borides of Zr, Nb, Ta, Ti and Hf. In addition, steel, nickel and copper alloys used in aircraft engines, space shuttles and turbine blades from aerospace materials were investigated. In addition, powder metallurgy and sintering techniques, which are the most widely used production methods of high temperature materials, are emphasized. In this study, important characterization techniques for analyzing some sample surface and subsurface properties are reviewed. Again, in this study, the use of AES, XPS, SSIMS and LEED methods for the chemical examination of surfaces is discussed. Optical, electron, and scanning probe microscopy is used for pictorial inspection of inspection specimens and structures, obtaining data on surface, shape, colors, and numerous additional physical properties. Here, AFM, SEM, TEM, EDX, FIB and EMP methods are discussed. Among the material analysis devices, XRD, x-ray fluorescence spectrometry, low energy electron diffraction, neutron diffraction and electron microprobe devices were examined
Microstructure, hardness and electrical properties of silver-based refractory contact materials
No full textWear properties of magnesium matrix composites reinforced with SiO<sub>2</sub> particles
No full textPurposeThe purpose of this paper is to improve the wear resistance and tribological properties of magnesium and its alloys in order to apply them to the friction components.Design/methodology/approachWear test, microhardness measurements, X‐ray diffraction (XRD), optical and electron microscopy examinations were applied.FindingsThe ceramic SiO2, which has different particle‐sized reinforced pure Mg‐SiO2 composites, is produced by powder metallurgy using high ball milling, pressing and sintering. Mg2Si and MgO intermetallic phases produced by powder metallurgy in the Mg‐SiO2 composite are dispersed as homogeneous into the Mg matrix. Mg‐SiO2 composites exhibited a lower wear rate than the unreinforced pure magnesium specimens. Despite the pure Mg, the wear resistance of the composite is 61 per cent and the wear volume decrease with reducing SiO2 particle size. The hardness of the composite is increased in a ratio of 70 per cent with the distribution of the Mg2Si and MgO phases into the Mg matrix.Practical implicationsIn this paper, pure Mg powder with purity of 99.9 per cent and SiO2 powders with a mean particle size of −500, −250, −125, −75 and −10 μm are mixed by mechanical alloying. The wear behaviour of Mg‐SiO2 composite, with the different particle‐sized composites dispersed with Mg2Si and MgO intermetallic phases under dry friction condition is studied. The microstructural and mechanical properties of composite material samples are determined by differential scanning calorimeter, XRD, microhardness, optical and scanning electron microscopy tests.Originality/valueSiO2 particles distributed in the matrix are effective to improve hardness and wear resistance when contacting counter materials. In the present study, the magnesium powders with different particle size SiO2 powders are mechanically alloyed with a Turbola Spex 80000 mixer.</jats:sec
DEVELOPING A KNOWLEDGE-DASED DECISION STEM TO SELECT THE STEELS OF DIESFOR SHEET-METAL FORMING
No full textMaterial selection is a problem solving and decison making process. In the selection of die materials, some points are very important. For this reasons, daıabases are not enough to select the steels of dies for sheet metal in themselves. They do not incorporate data relating to all of the contributin g factors needed for quantitive interpretations. To solve the user's problem are requried expertises and knowledge obtained from experts. In this study, a knowledg e-hased decision making system is introduced which is included the knowledge and experiences of the experts that subject fo ı med from rules and there is a database inc l uding the cbaracterictics of die steels. · In this syste m also comprises �ision making mechanizm that selects suitable die steels by using user inte rface
Effect of Nb addition on microstructural and mechanical properties of Ti-Nb based alloys produced by powder metallurgy
No full textİnsan sert doku ( kemik gibi) biyo-implant malzemeleri için Ti-Nb esaslı alaşımlar biyo-uyumları, mekanik özellikleri, korozyon dirençleri gibi özellikleri açısından umut vadeden malzemelerdir. Bu çalışmada, Nb ilavesinin, Ti-Nb ikili alaşımının mikroyapı ve mekanik özellikleri üzerine etkisinin incelenmesi amacıyla saf Ti, Ti-16Nb, Ti-26Nb alaşımları geleneksel toz metalürjisi yöntemi ile üretilmiştir. Sinterlenmiş numunelerin mikroyapısal gelişimleri ve faz analizleri optik mikroskop, SEM, EDS, XRD teknikleri kullanılarak belirlenmiştir. Sinterlenen Ti-Nb alaşımlarının mikroyapısının widmanstatten ?+? yapısından oluştuğu gözlemlenmiştir. Nb içeriğinin ağırlıkça %16'dan %26'ya artışı ile alaşımın mikrosertlik değeri 430 HV'den 327 HV'ye, eğme mukavemeti 1403 MPa'dan 1168 MPa'a ve elastik modül 103 GPa'dan 90 GPa'a düşmüştür. Mikroyapı da ise ?-fazı miktarı artarken, taneler incelmiştir. Elde edilen sonuçlar, toz metalürjisi ile üretilmiş TiNb alaşımlarının, klinik uygulamalarda en yaygın kullanılan Ti-6Al-4V alaşımının yerine tercih edilebileceğini göstermektedirTi-Nb based alloys are promising materials in terms of material properties, such as biocompatibility, mechanical properties and corrosion resistance for human hard tissuse (such as bone) bio implant materials. Present study focused on the effects of Nb addition on the microstructure and mechanical properties of Ti-Nb binary alloy. For this purpose, pure Ti, Ti-16Nb, Ti-26Nb alloys were produced by conventional powder metallurgy (PM) method. Microstructural development and phase analysis of sintered samples were determined by using optical microscopy, SEM, EDS, XRD techniques. It was observed that microstructures of sintered Ti-Nb alloys consist of widmanstatten α+β structure. With an increasing in the content of Nb (from 16 to 26 wt. %), the micro-hardness values of the alloys decrease from 430 HV to 327 HV, the bending strength of the alloys decreases from 1403 MPa to 1168 MPa and the elastic modulus of the alloys decreases from 103 GPa to 90 GPa. Also, it is worth noting that, finer grains achieved and the amount of the β-phase in the microstructure is increased with increasing Nb content. Results of the experimental works showed that PM Ti-Nb alloys could be offered as candidate materials for clinical practice applications as an alternative to Ti-6Al-4V allo
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