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Effects of sphere size on the microstructure and mechanical properties of ductile iron–steel hollow sphere syntactic foams

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International Journal of Minerals,Metallurgy and Materials 2016年第6期23卷 676-682页

作者： Hamid Sazegaran Ali-Reza Kiani-Rashid jalil vahdati khaki Department of Metallurgical and Materials Engineering Faculty of Engineering Ferdowsi University of Mashhad

The effects of sphere size on the microstructural and mechanical properties of ductile iron–steel hollow sphere（DI–SHS） syntactic foams were investigated in this study. The SHSs were manufactured by fluidized-bed coating via the Fe-based commercial powder–binder suspension onto expanded polystyrene spheres（EPSs）. Afterwards, the DI–SHS syntactic foams were produced via a sand-mold casting process. The microstructures of specimens were investigated by optical microscopy, scanning electron microscopy（SEM）, and energy-dispersive X-ray spectroscopy（EDS）. The microscopic evaluations of specimens reveal distinct regions composed of the DI matrix, SHS shells, and compatible interface. As a result, the microstructures and graphite morphologies of the DI matrix depend on sphere size. When the sphere size decreases, the area fractions of cementite and graphite phases are observed to increase and decrease, respectively. Compression tests were subsequently conducted at ambient temperature on the DI–SHS syntactic foams. The results reveal that the compression behavior of the syntactic foams is enhanced with increasing sphere size. Furthermore, the compressed specimens demonstrate that microcracks start and grow from the interface region.

关键词： ductile iron steel syntactic foams microstructure mechanical properties

Fabrication of Fe–TiC–Al_2O_3 composites on the surface of steel using a TiO_2–Al–C–Fe combustion reaction induced by gas tungsten arc cladding

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International Journal of Minerals,Metallurgy and Materials 2016年第2期23卷 193-204页

作者： Mahmood Sharifitabar jalil vahdati khaki Mohsen Haddad Sabzevar Department of Metallurgical and Materials Engineering Faculty of Engineering Ferdowsi University of Mashhad Department of Materials Engineering Faculty of Engineering University of Sistan and Baluchestan

The aim of the present study was to fabricate Fe-TiC-Al2O3 composites on the surface of medium carbon *** this purpose,TiO2-3C and 3TiO2-4Al-3C-xFe（0 ≤ x ≤ 4.6 by mole） mixtures were pre-placed on the surface of a medium carbon steel *** mixtures and substrate were then melted using a gas tungsten arc cladding *** results show that the martensite forms in the layer produced by the TiO2-3C ***,ferrite-Fe3C-TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO2-4Al-3C *** addition of Fe to the TiO2-4Al-3C reactants with the content from 0 to 20wt%increases the volume fraction of particles,and a composite containing approximately 9vol%TiC and A12O3 particles *** composite substantially improves the substrate *** mechanism by which Fe particles enhance the TiC ＋ A12O3 volume fraction in the composite is determined.

关键词： composite coatings iron-based materials combustion cladding microstructure microhardness

Effects of copper content on the shell characteristics of hollow steel spheres manufactured using an advanced powder metallurgy technique

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International Journal of Minerals,Metallurgy and Materials 2016年第4期23卷 434-441页

作者： Hamid Sazegaran Ali-Reza Kiani-Rashid jalil vahdati khaki Department of Materials Science and Metallurgical Engineering Engineering Faculty Ferdowsi University of Mashhad

Metallic hollow spheres are used as base materials in the manufacture of hollow sphere structures and metallic foams. In this study, steel hollow spheres were successfully manufactured using an advanced powder metallurgy technique. The spheres＇ shells were characterized by optical microscopy in conjunction with microstructural image analysis software, scanning electron microscopy（SEM）, energy-dispersive X-ray spectroscopy（EDX）, and X-ray diffraction（XRD）. The microscopic evaluations revealed that the shells consist of sintered iron powder, sintered copper powder, sodium silicate, and porosity regions. In addition, the effects of copper content on various parameters such as shell defects, microcracks, thickness, and porosities were investigated. The results indicated that increasing the copper content results in decreases in the surface fraction of shell porosities and the number of microcracks and an increase in shell thickness.

关键词： steel hollow spheres powder metallurgy copper content shell characteristics

Mechanochemical leaching of chalcopyrite concentrate by sulfuric acid

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International Journal of Minerals,Metallurgy and Materials 2016年第4期23卷 380-388页

作者： Farhad Khorramshahi Mohammadabad Sina Hejazi jalil vahdati khaki Abolfazl Babakhani Materials and Metallurgical Engineering Department Faculty of Engineering Ferdowsi University of Mashhad Materials and Metallurgical Engineering Department Faculty of Engineering University of Tehran

This study aimed to introduce a new cost-effective methodology for increasing the leaching efficiency of chalcopyrite concentrates at ambient temperature and pressure. Mechanical activation was employed during the leaching（mechanochemical leaching） of chalcopyrite concentrates in a sulfuric acid medium at room temperature and atmospheric pressure. High energy ball milling process was used during the leaching to provide the mechanochemical leaching condition, and atomic absorption spectroscopy and cyclic voltammetry were used to determine the leaching behavior of chalcopyrite. Moreover, X-ray diffraction and scanning electron microscopy were used to characterize the chalcopyrite powder before and after leaching. The results demonstrated that mechanochemical leaching was effective; the extraction of copper increased significantly and continuously. Although the leaching efficiency of chalcopyrite was very low at ambient temperature, the percentages of copper dissolved in the presence of hydrogen peroxide（H2O2） and ferric sulfate（Fe2（SO4）3） after 20 h of mechanochemical leaching reached 28% and 33%, respectively. Given the efficiency of the developed method and the facts that it does not require the use of an autoclave and can be conducted at room temperature and atmospheric pressure, it represents an economical and easy-to-use method for the leaching industry.

关键词： chalcopyrite mechanical activation mechanochemical leaching sulfuric acid cyclic voltammetry