International Journal of Materials Research Volume 108 Issue 12

International Journal of Materials Research

Volume 108 Issue 12

Contents
Journal Overview

November 25, 2017 Page range: 1023-1023

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Original Contributions

First principles, thermal stability and thermodynamic assessment of the binary Ni–W system

Iikka Isomäki, Marko Hämäläinen, Maria H. Braga, Michael Gasik November 25, 2017 Page range: 1025-1035

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Abstract

The Ni–W binary system was assessed using critically evaluated experimental data with assistance from first principles analysis and the CALPHAD method. The solution phases (liquid, fcc-A1 and bcc-A2) were modeled using the substitutional regular solution model. The recently discovered Ni 8 W metastable phase was evaluated as Fe 16 C 2 -like martensite with three sublattices, and shown to be possibly stable according to first principles calculations. Ni 8 W was also modeled as an interstitial compound, but the model is not good because the solubility of tungsten in nickel is very low, especially at low temperatures. There is no experimental evidence for such low solubility. The other binary compounds Ni 4 W and Ni 3 W were assessed as stoichiometric ones. Compared independent experimental and first principles data agree well with the calculated phase diagram using updated thermodynamic parameters.

Experimental evaluation of forming limit diagram and mechanical properties of nano/ultra-fine grained aluminum strips fabricated by accumulative roll bonding

Davood Rahmatabadi, Ramin Hashemi November 25, 2017 Page range: 1036-1044

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Abstract

In this research, for the first time, forming limit diagrams (FLDs) of ultra-fine grained Al/Al samples produced by accumulative roll bonding (ARB) process were evaluated. The samples were successfully prepared through ARB up to the 7 th pass. Mechanical properties, tensile fracture surfaces, and crystallite size of samples were investigated. The level of the FLD and elongation at first decreased and then increased, continuously. The results of tensile testing revealed that by increasing the number of ARB passes, the tensile strength increased continuously. Microhardness of Al strips increased and reached a value of 51 VHN after the seventh pass. Results of X-ray diffraction demonstrated that crystallite size decreased from 1 341 nm for annealed condition and it reached to 175 nm for ARBed samples after the 7 th pass. SEM images showed that the fracture mode in the ARBed samples was a shear ductile fracture with elongated sophomoric shear dimples.

FSW of bimodal reinforced Al-based composites produced via spark plasma sintering

Behzad Sadeghi, Morteza Shamanian, Fakhreddin Ashrafizadeh, Pasquale Cavaliere November 25, 2017 Page range: 1045-1054

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Abstract

Metal-matrix composites produced via spark plasma sintering are characterized by enhanced mechanical and microstructural properties. Obviously, the material behavior is strongly related to the reinforcement properties, in particular the reinforcement shape. The present paper is aimed at showing the friction stir welding of Al-based composites reinforced with different percentages of nano (2%) and microsized (8%) alumina particles. The joints, microstructural and mechanical properties were evaluated as a function of the different processing parameters such as rotating and advancing speeds of the tool. The joint evolution was related to the heat input during welding. The welded material fracture behavior showed different types of rupture compared to the spark plasma sintered material.

Modelling analysis and experiments of polycrystalline silicon directional solidification in an annular heating field

Xuli Zhu, Long Xu, Jinmei Huang, Hongqiong Wu November 25, 2017 Page range: 1055-1063

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Abstract

As a solution to the low convection strength of the Bridgman method and the convection control difficulties of the electromagnetic induction melting method, a novel, large directional solidification device with annular heaters arranged above the crucible is designed. The inhomogeneous heating field causes differences in melt density, intensifies controllable natural convection and accelerates the moving of impurities from the solid–liquid interface to the surface of the melt, thereby improving purification efficiency and reducing energy consumption. Although the temperature field is inhomogeneous, vertical crystal growth can still be achieved. Mathematical analytic modelling is used to explain the principle, and the feasibility is verified by experiments. The results show that high-quality and large bulk silicon ingot (1 m × 1 m × 0.45 m) can be produced at an average solidification rate of 3.68 μm s −1 .

Effect of flow, heat transfer and magnetic energy on the grain refinement of 7A04 alloy under electromagnetic pulse

Qingwei Bai, Yonglin Ma, Shuqing Xing, Xinyu Bao, Yanfei Feng, Wenxia Yu, Xiaolan Kang November 25, 2017 Page range: 1064-1072

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Abstract

In this paper, a transient numerical simulation method was used to analyze the direct chill casting process of 7A04 alloy under electromagnetic pulse treatment. The distribution and evolution of the electromagnetic force, fluid and thermal fields were studied to determine their effect on the solidification characteristics of alloy ingots. A modified nucleation theory for the refinement of grain size was presented considering the effect of electromagnetic energy on the critical Gibbs free energy ΔG*$\Delta {G^*}$ of the unity, which was verified by the corresponding experiments. The results showed that the swirl rings of the axial section in the melt were restrained and a lower temperature gradient was formed in the radial section when the magnetic flux intensity was increased. Under these conditions for nucleation, the grain refinement could be explained by the electromagnetic pulse energy that reduced the energy barrier and improved the nucleation rate, either heterogeneous nucleation or homogeneous nucleation.

A study on effects of a new two-step strain induced melt activation process on characteristics of Al 7075 alloy

Mostafa Karamouz, Mostafa Alizadeh, Alireza Ahmadi November 25, 2017 Page range: 1073-1080

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Abstract

It is well-known that the strain induced melt activation process results in a globular microstructure which improves the hardness and the ultimate tensile stress. However, its disadvantage is degrading some other properties such as elongation and formability due to the presence of continuous and brittle intermetallic compounds along with the formation of eutectic structures at grain boundaries. Hence, the aim of this research is to introduce a new process called two-step strain induced melt activation to overcome these drawbacks and to improve the microstructure and the formability of Al 7075 alloy. This new process yielded a globular structure and modified the microstructure. Also, the resultant precipitates were discontinuous with a more homogeneous distribution and the eutectic mixture was eliminated. Moreover, the alloy formability and the hardness were effectively enhanced by performing a rolling process.

Synthesis and characterization of mechanically alloyed cerium oxide reinforced Al-4.5Mg alloy composite

Sara Rastgarnia, Khalil Ranjbar, Khalil O. Gheisari, Gholam H. Borhani November 25, 2017 Page range: 1081-1089

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Abstract

Al-4.5Mg-0.5Mn alloy powders were mechanically alloyed by the addition of 1–3 wt.% cerium oxide (CeO 2 ) nanoparticles using a planetary ball mill under a dry argon atmosphere. A milling speed of 300 rpm and ball to powder ratio of 20:1 was used for all samples. An optimum milling time of 20 h was chosen considering the morphological and structural changes in the milled powders. The composite powders were consolidated via vacuum hot pressing at 515°C. Mechanical properties were evaluated by hardness and compression tests. The evolution of the structure and microstructure during the milling process was studied using X-ray diffraction and field emission scanning electron microscopy, respectively. The corrosion behavior of the samples was investigated by potentiodynamic polarization testing in a standard 3.5% chloride salt solution and assessed in terms of pitting potential and passivation range. CeO 2 reinforced mechanically alloyed Al-4.5Mg exhibited a major improvement in its hardness and compressive strength compared to the un-reinforced base alloy, i.e. 40 and 50% increment respectively. Nevertheless, the most important effect of CeO 2 incorporation was observed in the pitting resistance of the alloy.

Densification rate and interfacial adhesion of bilayer cemented tungsten carbide and steel

Oluwatosin Job Ojo-kupoluyi, Suraya Mohd Tahir, Azmah Hanim Mohamed Ariff, B. T. Hang Tuah Baharudin, Khamirul Amin Matori, Mohd Shamsul Anuar November 25, 2017 Page range: 1090-1098

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Abstract

Manufacturing tailored materials is commonly faced with the challenge of shrinkage mismatch between layers resulting in delamination. The effects of sintering temperature and carbon variation on the densification and interfacial bond strength of bilayer cemented tungsten carbide and steel processed through powder metallurgy are analyzed. It is revealed through field-emission scanning electron microscopy images that inter-layer diffusion induced by liquid-phase sintering plays a major role in the densification and bonding of layers. Through dimensional analysis of sintered bilayer specimens, the strain rate of cemented tungsten carbide is observed to surpass that of steel. An enhanced densification rate of 6.1 % and M 6 C (eta carbide) reduction with increased carbon level results in strong interfacial bonding in specimens sintered at 1 280 °C. At 1 295 °C, diffusion accelerates and the axial and radial shrinkage increase by 14.05 % and 13.35 %, respectively, in 93.8 wt.% WC – 6 wt.% Fe – 0.2 wt.% C and 93.2 wt.% Fe – 6 wt.% WC – 0.8 wt.% C, thereby increasing the tendency for complete delamination.

Short Communications

Cavitation erosion of 17-4 PH stainless steels following sub-zero treatment

Ion Mitelea, Ilare Bordeaşu, Ştefan-Eusebiu Katona, Corneliu Marius Crăciunescu November 25, 2017 Page range: 1099-1102

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Abstract

The effect of sub-zero treatment on 17-4 PH stainless steels is analysed based on ultrasonic cavitation experiments conducted on a vibratory machine with piezoceramic crystals. The results prove that the proposed treatment (solution treatment + sub-zero cooling + tempering), favours a reduction, by about 40%, of the mean depth of erosion, and mean depth erosion rate after 165 min of erosion by vibratory cavitation, compared to the solution treatment. The improvement of the cavitation erosion behaviour is explained based on hardness, metallographic and X-ray diffraction analysis.

Investigation on microstructure and thermal properties of in-situ synthesized Cu–ZrO2 nanocomposites

Marwa Elmahdy, Gamal Abouelmagd, Asaad A. Mazen November 25, 2017 Page range: 1103-1107

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Abstract

Cu–ZrO 2 nanocomposites were prepared by an in-situ reactive synthesis of copper nitrate Cu(NO 3 ) 2 and zirconium oxychloride ZrOCl 2 . Zirconia (ZrO 2 ) was added by 2.5, 5 and 10 wt.% to the Cu matrix to assess its effect on thermal conductivity and thermal expansion behavior. The results showed that ZrO 2 nanoparticles (30–50 nm) were homogeneously distributed in the copper matrix. The measured thermal conductivity for the Cu–ZrO 2 nanocomposites decreased from 372.8 to 94.4 W m −1 K −1 with increasing ZrO 2 content from 0 to 10 wt.%. Cu-10 wt.% ZrO 2 nanocomposite yields a low thermal conductivity of 94.4 W · m −1 K −1 along with a low coefficient of thermal expansion, 11.47 × 10 −6 K −1 .

DGM News

November 25, 2017 Page range: 1109-1109

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About this journal

The International Journal of Materials Research (IJMR) publishes original high quality experimental and theoretical papers and reviews on basic and applied research in the field of materials science and engineering, with focus on synthesis, processing, constitution, and properties of all classes of materials. Particular emphasis is placed on microstructural design, phase relations, computational thermodynamics, and kinetics at the nano to macro scale. Contributions may also focus on progress in advanced characterization techniques.
All articles are subject to thorough, independent peer review.