bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Chlorine Atoms for Development of Aluminum Corrosion
Authors: Yamashita Junko , Nunomura Norio
Published: November 2016

Computational density functional theory (DFT) model of the adsorption of chlorine atoms onto the perfect Al (111) surface has been performed. The structural and electronic properties of chlorine atoms adsorbed on the surface are investigated within a supercell approach for chlorine coverages of 0.25, 0.33, 0.5 and 1 ML respectively. It is found that the adsorbates prefer on-top sites over bridge, hcp and fcc sites in low coverage while fcc sites in high coverage, and the binding energy decrease with increase of coverage due to the interactions of chlorine atoms. The discussion of geometrical and electronic analysis by plotting differential charge density distribution and projected density of states (PDOS) are presented.
Initiation and Propagation Behaviors of Small Crack in a Polycrystalline Ni-Base Superalloy under Thermo-Mechanical Fatigue Loading
Authors: Yamazaki Yasuhiro
Published: November 2016

In this work, the initiation and propagation behaviors of naturally initiated small crack in a polycrystalline Ni-base superalloy under the several kinds of thermos-mechanical fatigue (TMF) conditions. The effect of phase angle between temperature and strain cycles in TMF loading on the initiation and propagation behavior of small crack was discussed. The experimental results revealed that the initiation and propagation morphologies of fatigue small crack were affected on the phase angle; the crack initiation mode was changed from the intergranular mode to the transgranular mode with the increasing of the phase angle in this study. On the other hand, when the crack growth rates of naturally initiated small crack are correlated with fatigue J-integral range, the effect of the phase angle on the small crack growth rates became negligible even if the crack propagation mode depended on it.
Effect of Added Elements on Microstructures and Joint Strength of Lead-Free Sn-Based Solder Joint Dispersed IMC Pillar
Authors: Hayashi Yawara , Shohji Ikuo , Nakata Yusuke , Hashimoto Tomihito
Published: November 2016

To create a high reliability solder joint using IMCs dispersed in the joint, the joints with four types of lead-free solder were investigated. The joint with Sn-3.0Ag-0.7Cu-5.0In (mass%) has high die shear force compared to other joints investigated, and the joint with the Ni-electroplated Cu bonded at 300 oC for 30 min showed the maximum die shear force due to formation of a large number of fine IMCs. In the joint with Sn-0.7Cu-0.05Ni (mass%), uniform dispersion of a large number of IMCs was achieved, although the die shear force of the joint is lower than that of the joint with Sn-3.0Ag-0.7Cu-5.0In. In the joint with Sn-5.0Sb (mass%), a solder area was remained in the center of the joint although a large number of columnar IMCs form at the joint interface. The die shear force of the joint with Sn-5.0Sb increased with increasing the bonding time due to formation and growth of IMCs. In the joint with Sn-3.0Ag-0.5Cu (mass%), IMCs formed at the joint interface and did not disperse in the entire joint.
Microstructure and Property of Fe-Based Alloy Modified Layer on 304 Stainless Steel by High-Energy Pulse Laser-Like Cladding (HPLC)
Authors: Zhang C.H. , Jia Y.F. , Guan M. , Wu C.L. , Tan J.Z. , Zhang S.
Published: November 2016

Fe-based alloy modified layers were prepared on 304 stainless steels by high-energy pulse laser-like cold welding cladding technique. The microstructure, composition and phase constituents of the cladding layers were analyzed using SEM, EDS and XRD, respectively. The microhardness, friction-wear and cavitation erosion resistance were also investigated using microhardness tester, pin-on-disk wear-testing machine and ultrasonic vibrator. Experimental results showed that Fe-based alloy modified layer was mainly composed of α-Fe matrix phase and skeleton-like Cr23C6, Cr7C3 carbide reinforced phase, which was dispersively distributed into α-Fe matrix. The microhardness and friction coefficients of Fe-based alloy modified layer were 600HV and 0.4, respectively, indicating an improved wear resistance. The weight loss rate and average erosion depth of the modified layer was 1/5 and 1/10 that of 304 stainless steel in 3.5% NaCl solution after 5-h cavitation erosion test, respectively. The erosion crater depth of the modified layer was uniform, indicating that the cavitation erosion resistance of the modified layer was much better than that of the 304 stainless steel.
Effect of Temperature and Strain Rate on the Mechanical Properties of 99.5 Aluminium Rods Extruded by KOBO
Authors: Boczkal Sonia , Lech-Grega Marzena , Szymanski Wojciech , Ostachowski Paweł , Lagoda Marek
Published: November 2016

In this study, aluminium rods were cold extruded in a direct process by KOBO method in two variants: variant I with varying (decreasing) frequency of die oscillations necessary to maintain a constant extrusion force, and variant II with constant frequency of die oscillations, leading to a decrease in the extrusion force. The tensile test of rods was carried out in a temperature range of 20 - 200°C and at a strain rate from 8xE10-5 to 8xE10-1 s-1. Significant differences in the elongation of the tested rods were observed. It was found that rods extruded at variable die oscillations and stretched at room temperature had similar elongation, independent of the strain rate. With the increase of temperature, the elongation of samples stretched at a low speed was growing from a value of about 8% at room temperature up to 40% at 200°C. At high strain rates, despite the increasing temperature, the elongation remained at the same level, i.e. 5-6%. In rods extruded at constant die oscillations, the elongation at a low strain rate was growing with the temperature from 10% at room temperature up to 29% at 200°C. At high strain rates, the elongation decreased from 28% at room temperature to 11% at 200°C. The results were interrelated with examinations of the structure of rods and fractures of tensile specimens. In the material extruded by KOBO method with constant die oscillations, the beginnings of the recrystallization process were observed, absent in the material extruded at variable die oscillations.
Effect of Mischmetal Additions and Solution Heat Treatments (T4) on the Microstructure and Mechanical Properties of Thixocast ZK60-RE Magnesium Alloys
Authors: da Silva Erenilton Pereira , Buzolin Ricardo Henrique , Callegari Bruna , Warchomicka Fernando Gustavo , Requena Guillermo C. , Pinto Haroldo Cavalcanti
Published: November 2016

Solution treatments (T4) at 380 °C for 16 h and 500 °C for 8 h were performed for ZK60 magnesium alloys modified with addition of 0.5, 1.5 and 2.5 wt% of mischmetal (combination of rare-earth (RE) elements). The compression behaviour was investigated at room temperature and at 300 °C correlated with the microstructure and differential scanning calorimetry (DSC) data. The as-cast microstructure is formed by a-Mg matrix with globular grains reinforced by a semi continuous network of Mg-Zn, Mg-Zn-RE and Mg-RE intermetallic particles. Solution-treated alloys show lower yield strengths due to partial dissolution of precipitates. Work hardening was not observed for the alloys compressed at 300°C with the compression speed of 10-3 s-1, whereas it was observed for the compression speed of 10-2 s-1 for the all as-cast, ZK60-1.5RE-T4 at 380 °C and ZK60-1.5RE-T4 at 380 °C.
Evolution of Recrystallization Textures in Cold-Rolled Commercially Pure Aluminum
Authors: Lee Dong Nyung
Published: November 2016

The evolution of recrystallization texture in commercially pure aluminum sheet cold-rolled by 90% reduction in thickness was measured by Juul Jensen et al. The cold-rolling texture consisted of the Goss {110}<001>, Brass {110}<112>, S {123}<634>, and copper {112}<111> components. When the cold-rolled aluminum sheet was annealed at temperatures between 253 and 341°C for times between 5 min and 20 h., the cube {001}<100> component evolved. The evolution of the cube texture cannot be explained by either the oriented nucleation theory by Burgers and Louwerse or the oriented growth theory by Barrett. The cube texture evolution originates from the Copper component by the strain-energy-release-maximization (SERM) theory by Lee. Once the Cube oriented, dislocation free nuclei evolve, they are in the best position to grow at the expense of neighboring deformed high energy grains of the Goss, Brass, S, and Copper orientations, and the volume fractions of the Goss, Brass, S, and copper components would decrease. However, the volume fraction of the Goss component increased a little at annealing temperatures of 253 and 278°C, at variance with expectation. Low stacking-fault-energy alloys with the brass {110}<112> rolling texture evolve the {236}<385> texture after recrystallization, whereas high stacking-fault-energy alloys with the brass rolling texture evolve the Goss texture after recrystallization by the SERM theory, resulting in the increase of the volume fraction of the Goss texture.
Superplasticity of Friction-Stir Welded Al-Mg-Sc Alloy with Ultrafine-Grained Microstructure Obtained by Warm Severe Plastic Deformation
Authors: Malopheyev Sergey , Mironov Sergey , Vysotskiy Igor , Kaibyshev Rustam
Published: November 2016

High-strength sheets of Al-5.4Mg-0.2Sc-0.1Zr alloy were produced by equal-channel angular pressing (ECAP) to 12 passes via route BC at 300 °C (573 K) followed by isothermal rolling at 300 °C (573 K) to a total thickness reduction of 80%. The final sheets with ultra-fine grained (UFG) structure were joined by friction stir welding (FSW). The tensile samples including all of the characteristic FSW microstructural zones were machined perpendicular to welding direction. The material demonstrated excellent superplastic properties in the range of temperatures from 350 (623 K) to 450 °C (723 K) at strain rates ranging from 8.3×10-3 s-1 to 3.3×10-1 s-1. The base material was found to be prone to abnormal grain growth at the testing temperature. This led to localization of the superplastic deformation in the stir zone section of the joints and thus limited total elongation-to-failure. The relationship between superplastic ductility and microstructure and application of this technique for the fabrication of large-scale superplastic sheets are discussed.
The Effect of Thermomechanical Processing Temperature-Strain-Time Parameters on the Mesostructure Formation
Authors: Kodzhaspirov G.E. , Rudskoi Andrey
Published: November 2016

The effects of Temperature-Strain-Time parameters at the Thermomechanical Processing (TMP) of austenitic, duplex and pearlitic structural steels on the mesostructure formation has been studied based on the laboratory, industrial experiments and TEM analysis. The fragmented dislocation substructure observed in steels with a different carbon, nitrogen, titanium, niobium content as well as recrystallization gave evidence that TMP effects the work-hardening and softening behaviour. The problem of mesostructure appearing in various steels and alloys due to various modes of TMP used hot and hot-warm deformation is discussed. The role of plastic strain in the formation of mesostructure and the relation between the changes in the crystal structure due to TMP and the mechanical properties of the steels are considered.
Effects of Magnetic Field Intensity on Carbon Diffusion in Pure Iron in Paramagnetic Ferrite Region
Authors: Zhang Zhi Wei , Wu Yan , Zhao Xiang
Published: November 2016

Effects of magnetic field intensity on carbon diffusion in pure iron in paramagnetic ferrite region above the Curie temperature were investigated using carburizing technology. It was found that the magnetic field intensity can significantly affect the carbon diffusion behavior in pure iron in paramagnetic ferrite region in the direction parallel to the magnetic field direction, both the carbon diffusion coefficient and the average carbon diffusion distance increase gradually with the increasing of the magnetic field intensity. Magnetic field annealing obviously promotes the carbon diffusion in pure iron in the direction parallel to the magnetic field in paramagnetic ferrite region above the Curie temperature, and promotion effect increases with the enhancement of the magnetic field intensity. The structure defects made by the magnetic field may cause the increasing of carbon diffusion flux.
Microretina: An “Open Source” Tool for Retinal Images Analysis
Authors: Bonaiuto Vincenzo , Gabrieli Massimo , Sargeni Fausto
Published: November 2016

Several are the instrumental tests currently available in the diagnosis of retinal diseases. Their outputs are typically images of anatomical portions of the eye. However, these are useful to highlight only few aspects of the characteristic lesions of the occurring pathology. For this reason, the clinician needs to have tools able to perform comparative analysis of the different diagnostic images by using procedures of integration of the different clinical information contained in each of them.
In this paper, we will describe a new medical software tool (MicroRetina) tailored for the comparative analysis of images of the fundus oculi, acquired during diagnostic tests that make use of different medical instruments. The developed software is an open system able to manage images acquired by different instruments and it will be able to give a helpful support to one of the existing problem in performing diagnosis by using images of the fundus oculi. In particular, it will allow the clinician to perform in real time the comparative analysis of the different clinical findings allowing him to have further diagnostic information not otherwise available by the analysis of the single images only.
Solid-State Bonding of 5052 Aluminum Alloy/316L Stainless Steel by Using Organic Salt Formation/Decomposition Reaction
Authors: Saito Hiroki , Koyama Shinji
Published: November 2016

The effect of metal salt coating process on the bond strength of the bonded interface of 5052 aluminum alloy and 316L stainless steel was investigated by SEM observations of interfacial microstructures and fractured surfaces. Aluminum alloy surfaces were coated by boiling in 5% aqueous solution of NaOH for 5 s and 98% formic acid and 99.7% acetic acid for 20 s and 20 s respectively. Bonding process was performed at bonding temperature of 733 ~ 773 K under a pressure of 20 MPa (bonding time of 900 s). From this study, it is found out that the bonded strength of the joint increased with the rise in bonding temperature with or without metal salt coating process. However, it is understood that with metal salt coating process, high strength joint can be achieved with lesser deformation and lower bonding temperature. From the experimental results, it is found out that metal salt generation processing is effective at removing oxide film and substitution to a metal salt on the aluminum surface.
Influence of a Direct Current on the Solidification of Immiscible Alloys
Authors: Jiang Hong Xiang , Sun Qian , Zhao Jiu Zhou
Published: November 2016

Continuous solidification experiments were carried out with immiscible alloys under the effect of a direct current. The experimental results demonstrate that a direct current shows a significant effect on the migration of minority phase droplets (MPDs) in continuously solidified immiscible alloys. It can promote the formation of a well dispersed microstructure or a core/shell microstructure. A model describing the kinetics of the microstructure evolution in a continuously solidified immiscible alloy was developed. The microstructure formation in the alloys was calculated. The numerical results are in favorable agreement with the experimental ones. They demonstrate that a direct current may affect the microstructure development through changing the spatial motions of MPDs. The alloys show a well dispersed microstructure when they are solidified with such a direct current density that the direct current causing motion of the MPDs is almost equivalent to the radial component of the Marangoni migration velocity of the MPDs. The alloys show a core/shell microstructure when they are solidified with such a direct current density that the direct current causing motion of the MPDs dominates the migration of the MPDs along the radial direction of the sample. A wire or rod with well dispersed microstructure or a core/shell microstructure can be prepared by solidifying immiscible alloys under the effect of a direct current properly chosen.
Thermo-Mechanical and Low Cycle Fatigue Failure Behavior Relevant to Temperature Regime in a TBCed Superalloy Specimen
Authors: Okazaki Masakazu , Yamagishi Satoshi , Yonaguni Yuuki
Published: November 2016

Steady state and non-steady state thermo-mechanical fatigue failure is great concern in this work. At first steady state thermo-mechanical fatigue failure behavior was investigated using the round-bar TBC specimens, after getting basic data of mechanical properties of the bond/top coats and the substrate alloy. The failure behavior was compared with that during isothermal low cycle fatigue (LCF). Next non-steady state TMF tests were carried out in which non-steady state thermal stress was significant in the TBC specimen, compared with the properties under the steady state TMF. The experimental work clearly demonstrated that the TMF failure lives were significantly changed depending on the temperature regime during TMF and LCF. Of particular importance was found in the non-steady state TMF tests. The non-steady state TMF cycling promoted the delamination of ceramic top coat, resulting in a significant reduction in fatigue life.
Osteoconductivity of Superhydrophilic Ti- and Zr-Alloy for Biomedical Application
Authors: Okido Masazumi , Kuroda Kensuke
Published: November 2016

Surface hydrophilicity is considered to have a strong influence on the biological reactions of bone-substituting materials. However, the influence of a hydrophilic or hydrophobic surface on the osteoconductivity is not completely clear. In this study, we produced super-hydrophilic and hydrophobic surface on Ti-and Zr-alloys. Hydrothermal treatment at 180 oC for 180 min. in the distilled water and immersion in x5 PBS(-) brought the super-hydrophilic surface (water contact angle < 10 (deg.)) and heat treatment of as-hydrothermaled the hydrophobic surface. The osteoconductivity of the surface treated samples with several water contact angle was evaluated by in vivo testing. The surface properties, especially water contact angle, strongly affected the osteoconductivity and protein adsorbability, and not the surface substance.
Superelasticity of Ti-Nb-Zr Alloys and their Medical Application
Authors: Isaenkova Margarita , Perlovich Yuriy , Efimova Elizaveta , Zhuk Dmitry , Krymskaya Olga
Published: November 2016

In this paper investigation results of behavior of promising superelastic alloys of Ti-Nb-Zr system in blood-vessel are presented. The possibility of their use in manufacturing of medical stents is examined. Based on analytical review of present scientific papers, four different alloys of Ti-Nb-Zr system are taken in consideration. A finite element modelling of stent behavior during delivery and opening stages is considered. These processes are done for two typical stent geometries and four alloys possessing different mechanical properties. Finite modelling results are analyzed to show the distribution of internal stresses, mechanical aspects of stent installation and effectiveness of various configurations to widen the narrowed vessel. Modeling has allowed to formulate recommendations for optimal mechanical characteristics of the superelastic alloy used for the manufacture of medical stents.
Thermal Plasticity Index of Nanostructured N-Based Coatings on HSS 6-5-2 (1.3343) Tool Steel
Authors: Cabibbo Marcello , Clemente Nicola , Musharavati Farayi , Spigarelli Stefano
Published: November 2016

Nowadays, cutting tools, designed to be used for machining without lubricants, are developed to improve the high working speed capabilities. With this respect, quaternary Ti-and N-based coatings are able to significant increase hardness, wear resistance and high temperature oxidation resistance. One of the major drawbacks still consists on the limited thermal stability of such coatings, which is reported to be about 600°C. In the present study, thermal stability studies of a nanostructured multi-layered N-based (AlTiCrxN1-x) coating on a HSS 6-5-2 tool steel were carried out. Two quantities were calculated out of the hardness and elastic modulus of the coatings. One is the ratio H/E that represents the coating resistance to compression without failure; another one is H3/E2, which provides information on the specific contact pressure limit without failure. It was found that, by using the less demanding thermal cycling mode, the coating ability to plastically deform without damage, is retained up to 800-1000°C. The highest, and more effective coating plasticity index was obtained by using the less demanding cycling mode, while, the other two modes induced a continuous index decrease with temperature.
Fracture Surface Characterisation of Friction Stir Processed Magnesium Alloy after Mechanical Tests
Authors: Cerri Emanuela , di Giovanni Maria Teresa , Rimoldi Tiziano , Cristofolini Luigi
Published: November 2016

A high pressure die cast Mg-9%Al-1%Zn alloy was friction stir processed at two high rotation rates and advancing speeds. Tensile tests were performed at higher temperature to study the mechanical properties of the microstructure induced by the friction stir process. Fracture surfaces resulting from tensile tests were observed by scanning electron microscopy and investigated by microanalysis. The fracture occurred in the tmaz and inside the stirring zone, depending on deformation conditions (temperature and strain rate). The morphology of the fracture surface varied from ductile to brittle in the same sample depending on phase type. Microhardness was measured on cross sections perpendicular to the advancing direction of the stirring pin, at various depth levels, before performing tensile tests to estimate the attitude of a single region to be deformed.
Analysis of Deformation and Internal Defect in Flat-Wedge Cross-Wedge Rolling of GH4169 Superalloy
Authors: Chen Yan , Gan Hong Yan , Zhang Shi Hong , Cheng Ming , Song Hong Wu
Published: November 2016

The deformation and internal defect in the flat-wedge cross-wedge rolling (CWR) of GH4169 superalloy were investigated numerically using a coupled thermo-mechanical finite element analysis (FEA) model. The simulation analysis showed that the temperature distribution in the work piece was non-uniform during the flat-wedge CWR. When the initial temperature of the work piece was relatively low, the work piece temperature increased, a heating effect of the plastic deformation, while relatively high initial work piece temperatures resulted in cooling the work piece, caused by the work piece contact with the tools. It is noted that the increase of tools moving speeds is helpful to reduce the generation of internal defects in the flat-wedge CWR of GH4169 alloy. An important tendency is that both increasing the tools temperature and decreasing friction coefficient all can contribute to avoiding the center defects in the flat-wedge CWR of GH4169 alloy
The Effect of Final Annealing Heating Rate on Abnormal Grain Growth in a Fe-3.5%Si Steel
Authors: Citrawati Fatayalkadri , Quadir Md Zakaria , Munroe Paul
Published: November 2016

In this study the effects of heating rate on the sharpness and size of Goss oriented ({110}<001>) grains during secondary recrystallization annealing at 900 °C was observed. The results show that, at the same annealing temperature, rapid heating of the samples to this temperature generates a higher drag force compared to a slower heating rate (5°C/min). The two groups of samples show different growth kinetics for Goss grains, in which at the longest annealing time, the rapid heating sample exhibits larger maximum Goss grain size compared to the slower heated samples.
Tensile Stress Analyses through Digital Image Correlation of Single Lap Joints of High Strength Steel and Aluminum Alloy Using Adhesive Bonding
Authors: Bamberg P.A.M.G.P. , Reisgen Uwe , Marx B. , Barbosa J.D.V. , Coelho R.S.
Published: November 2016

Structural adhesives methods for joining multi material sheets have been focus of studies and researches for the last years. The most common and widely known type of test is the tensile test of single lap joints (SLJ). However, there are opportunities for analyzing the mechanical performance of such method in SLJ with materials of different properties, such as ductile structural aluminum alloys and high strength steels. It’s also known that the stress state of SLJ, when stressed longitudinally, generates secondary forces. One of them is known as cleavage force which initially leads to the failure of bonded joints. The aim of this work is to analyze the stress state of similar and dissimilar materials SLJ submitted to tensile stresses and also the influence of some variables, such as overlap length, adhesive film thickness and adherend yield limit, over the stress strength of the samples. As adherend materials it was selected the structural aluminum alloy AA 5083 H111 and the high strength steel DP600. At the end of this work it is expected to understand the proper stress state of the SLJ when using similar and dissimilar materials, identifying stress concentrators that bring the structure to fail, using the Digital Image Correlation (DIC) method. It was discovered that the yield strength associated with the overlap length highly influences the SLJ strength, by leading it to a close to pure adhesive shear stress state.
Fatigue Crack Growth in Flow Formed INCONEL 718
Authors: Coleman Costa , Bache Martin R. , Boettcher Carl
Published: November 2016

Fatigue crack propagation has been measured in flow formed Inconel 718 (IN718). Test pieces were extracted from a flow formed tubular structure in the longitudinal direction, retaining the tube curvature across their width. Crack growth rates (da/dN) were measured at 20, 300, and 400oC. For comparison, tests were repeated on specimens with an identical geometry but machined from conventionally forged IN718. Detailed metallurgy of the flow formed material is presented.
Materials Research at University of Nevada, Las Vegas
Authors: Kumar Ravhi S. , Gabrimicael Weldu , Cornelius Andrew L.
Published: November 2016

High-pressure studies on thermoelectric materials allow the study of the relationship between structural, elastic, and electronic properties. The High Pressure Science and Engineering Center (HiPSEC) at UNLV performs interdisciplinary research on a wide variety of materials at high pressures. One such system, CrSi2 is an indirect band gap semiconductor that has potential applications in solar cells.
Manganese Effect on Q&P CMnSi Steels
Authors: di Schino Andrea , Braccesi Claudio , Cianetti Filippo , di Nunzio Paolo Emilio , Mengaroni Sabrina , Calvillo Pablo Rodriguez , Cabrera Josè Maria
Published: November 2016

The present study is focused on analyzing the effect of Mn amount in two experimental steel compositions, specially designed for Quenching and Partitiong (Q&P), 0.15C-2.5Mn-1.5Si and 0.15C-3Mn-1.5Si without significant contribution of Al. Two-Step Q&P thermal treatments were performed at laboratory scale in a quenching dilatometer Bähr DIL805A/D. The fractions of retained austenite were evaluated by X-ray diffraction techniques. The mechanical properties of the Q&P samples were evaluated, a strong dependence of strength, uniform elongation and strain hardening values on process parameters has been found. Higher uniform elongation were related to higher residual austenite contents. The 0.15C-3Mn-1.5Si steel showed systematically the largest mechanical values with respect to the 0.15C-2.5Mn-1.5Si steel.
Microstructure and Texture Evolution in Nickel during Accumulative Roll Bonding
Authors: Duan Jia Qi , Quadir Md Zakaria , Ferry Michael
Published: November 2016

Microstructure and texture evolution of commercially pure Ni processed by accumulative roll-bonding (ARB) up to eight cycles were studied using electron back scattered diffraction (EBSD). During ARB processing, the original coarse equiaxed grains were gradually transformed into refined lamellar grains along the rolling direction (RD). Shear bands started forming after three cycles. The fraction of low angle grain boundaries (LAGBs) increased after the first and second cycle because of orientation spreading within the original grains. However, their fraction decreased with the evolution of high angle grain boundaries (HAGBs) during subsequent deformations, until saturation was reached after six cycles. Overall, the typical deformation texture components (S, Copper and Brass) were enhanced up to six ARB cycles and then only Copper was further strengthened. At higher cycles a higher Copper concentration was found near sample surface than the interiors due to a high frictional shear of ARB processing.
Effect of Microalloying Elements on Phase Transformation, Microstructure and Mechanical Properties in Dual-Phase Steels
Authors: Bocharova Ekaterina , Khlopkov Kirill , Sebald Roland
Published: November 2016

Dual-phase steels are the most important AHSS grades for automotive applications. Microalloying elements such as Ti, Nb or B are widely used to improve the strength of dual-phase steels. Thus, understanding the influence of these elements on the microstructure and mechanical properties of dual-phase steels along the processing route is critical for the development of new steel grades. In this work, different microalloying elements were investigated, separately or in combination. The influences of the different elements on the microstructure and mechanical properties of dual-phase steels in the hot-rolled condition and after annealing of cold-rolled material. Dilatometer measurements were performed to investigate phase transformation during a typical continuous annealing treatment of dual-phase steel after cold rolling. It was shown that, for example, Ti has a strong influence on the mechanical properties of hot-rolled material while its influence on annealed materials after cold rolling was relatively small. Conversely, B had a strong influence on cold-rolled materials but an insignificant influence on hot-rolled materials.
Determination of Crystallographic Orientation near a Chill Zone Using Ghost Lines
Authors: Esaka Hisao , Shinozuka Kei
Published: November 2016

Many crystals nucleate on the mold surface when the molten alloy is poured in a mold cavity. Because the crystallographic orientations of these crystals are random, the solidified structure near the mold surface is very complex. The ghost lines, which are sometimes thick and the angle between them is not 90 degrees, are often observed in this region. However, if the crystallographic structure of this alloy is cubic, such as bcc or fcc, the ghost lines are very regular. In order to understand the geometry of ghost lines, Al-20 mass%Cu alloys were unidirectionally solidified with constant growth velocity. The solidified structures on the obliquely crossed section were observed. The ghost lines were quite regular and parallel to each other in a solidification grain. The angles and the ratio of the width of ghost lines were measured and crystallographic orientations were estimated using these parameters, based on the solid analytical geometry. EBSD analysis were also performed on the area, where the ghost lines were characterized, and the precise crystallographic orientations were decided. The comparison between both analytical values indicated that the differences between them are within 10 degrees and it can be safely concluded that the estimation for crystallographic orientation using ghost lines agreed well with the EBSD analysis.
Microstructure and Mechanical Properties of Mg-6Zn-1.4Y Alloy Produced by Rheo-Squeeze Casting Process
Authors: Fang Xiao Gang , Wu Shu Sen , Lü Shu Lin
Published: November 2016

Mg-Zn-Y alloys containing a thermally stable icosahedral quasicrystal phase (I-phase) will have wide application future on condition that primary α-Mg dendrite and the I-phase can be refined during the casting process. In this research, the microstructure and mechanical properties of the rheo-squeeze casting (RSC) Mg-6Zn-1.4Y alloys have been investigated. The Mg alloy melt was exposed to ultrasonic vibration (USV) with different acoustic power densities from 0 W/mL to 9 W/mL, and then the slurry was formed by squeeze casting. The results show that good semi-solid slurry with fine and spherical α-Mg particles could be obtained with the acoustic power density of 6 W/mL, and the average grain size and shape factor of primary α-Mg were 32 μm and 0.76, respectively. Meanwhile the coarse eutectic I-phase (Mg3Zn6Y) was refined obviously and dispersed uniformly. Compared with the samples without USV, the tensile strength and elongation of the RSC casting samples with 6 W/mL acoustic power density were elevated by 10.6% and 55.5%, respectively.
Microstructural Evolution in a 9%Cr-3%Co-3%W-VNb Steel during Creep
Authors: Fedoseeva Alexandra , Dudova Nadezhda , Kaibyshev Rustam
Published: November 2016

Microstructural evolution in a 9Cr-3Co-3W-0.2V-0.06Nb-0.05N-0.005B steel crept at T=650°C under an applied stress of 140 MPa up to strains of 1, 3, 5.75 and 12%, which represent primary, secondary and tertiary creep stages and rupture, respectively, was studied. The steel was initially normalized from 1050°C, and finally tempered at 750°C for 3h. After tempering the boundaries of tempered martensite lath structure (TMLS) were decorated by M23C6 carbides, M6C carbides and Laves phase particles. The 3% W additives provide the narrow size distribution of the boundary particles excepting M6C carbides. The depletion of thermodynamically none-equilibrium content of W from the solid solution during creep leads to following events. (i) Continuous precipitation of small Laves phase particles occurs during all creep stages and results in the formation of bimodal size distribution. As a result, the average size of Laves phase particles remains unchanged during creep. (ii) Coarsening of M23C6 carbides starts to occur only at the transition to tertiary creep. (iii) Transformation of laths to subgrains followed by their growth is observed during all stages of creep. The density of particle located at lath/subgrain boundaries decreases from 5.6 to 2.6 μm-1 during creep up to rupture. However, no full transformation of TMLS into subgrain structure has been revealed.
Plasticity and Size Effects in High Purity Cobalt: An Experimental Study
Authors: Fleurier Gwendoline , Martinez Mayerling , Dubos Pierre Antoine , Hug Eric
Published: November 2016

The occurrence of size effects in cobalt was examined by the analysis of mechanical properties of samples with thickness t, in a large range of grain size d giving a number of grains across the thickness t/d. On Hall-Petch plots, from the very beginning of plastic strain, two linear behaviors are notable: the polycrystalline one for higher t/d and the multicrystalline one for lower t/d in which the flow stress is strongly reduced. (t/d)c is the threshold value between the two behaviors taking a value of around 14. This high value is directly linked to the low stacking fault energy of cobalt. The microstructure of the polycrystalline samples exhibits a strong basal texture and a small proportion of a secondary face-centered cubic phase in a hexagonal close-packed main phase was evidenced. TEM analysis enables to characterize the dislocations and the stacking faults present in the two phases. To complete the analysis, two plasticity stages can be distinguished: stage A corresponding to dislocations gliding and stage B driven by twinning. Size effects in cobalt are found to occur during gliding process and could be related to surface effects as previously shown in face-centered cubic metals.
Modelling Methods of Magnetohydrodynamic Phenomena Occurring in a Channel of the Device Used to Wash out Spent Automotive Catalyst on Metallic Substrate by a Liquid Metal
Authors: Fornalczyk Agnieszka , Przylucki Roman , Golak Sławomir , Saternus Mariola
Published: November 2016

The recovery of precious metals is necessary for environmental and economic reasons. Spent catalysts from automotive industry containing precious metals are very attractive recyclable material because as the devices. they have to be periodically renovated and eventually replaced. Among automotive catalysts withdrawn from use, these with metallic carrier constitute quite a big group. Metallic carriers are usually obtained from steel FeCrAl , which is covered by a layer of PGM acting as a catalyst. World literature describes a number of pyro-or hydrometallurgical methods used for recovery of platinum from used automobile catalytic converters. However, all methods, available in the literature, are used to recover platinum from ceramic carrier. This paper presents the new method of removing platinum from the spent catalytic converters applying lead as a collector metal in a device used to wash out platinum by using mangetohydrodynamic pump. The article includes the description of the methods used in modelling magnetohydrodynamic phenomena (coupled analysis of the electromagnetic, temperature and flow fields) occurring in this particular device for this kind of waste. The general phenomena and ways of coupling the various physical fields for this type of calculation have also been described. The basic computational techniques with a discussion of their advantages and disadvantages have been presented.
Modelling the Local Microstructure Properties due to Multi-Pass Welding
Authors: Genchev Gancho , Doynov Nikolay , Ossenbrink Ralf , Michailov Vesselin
Published: November 2016

The paper presents an advanced simulation approach developed for considering the local microstructure properties variation due to multiple heat treatment. The model describes the resulting microstructure as a function of the peak temperature, austenisation time, cooling time and takes into account the microstructure formed after each thermal cycle. The model is calibrated with experimental material data obtained by repeated thermal loads. It is qualified to calculate the hardness and local microstructure properties in the HAZ of multi-pass welds. Thermo-mechanical simulation of the residual welding stresses and distortions in multi-pass welded joint is performed and validated by measurements.
Effect of Boron Addition on Microstructure and Mechanical Properties of AZ84 Mg Alloy
Authors: Won Ju Hyun , Min Seok Hong , Ha Tae Kwon
Published: November 2016

Effect of B addition on the microstructure and mechanical properties of AZ84 Mg alloy was investigated in this study. Through calculation of phase equilibria of AZ84 Mg alloy, carried out by using FactSage® and FTLite database, solution treatment temperature was decided as temperature of 330oC, where supersaturated solid solution can be obtained. Solid solution treatment of AZ84 Mg alloy was successfully conducted at 330oC and supersaturated microstructure with all almost all phases resolved into matrix was obtained. After solution treatment, hot rolling was successfully conducted by reduction of 60%. Compression and tension tests were carried out at room temperature on the samples in as-cast, solution treated, hot-rolled and subsequently recrystallized states. After solid solution treatment, each alloy was soaked at temperatures of 180 and 200oC for time intervals from 1 min to 48 hrs and hardness of each condition was measured by micro-Vickers method. Peak aging conditions were deduced as at the temperature of 200 oC for 10 hrs for ZA84 Mg alloy. By addition of boron, aging kinetics was expedited and strength was enhanced.
Anelastic Phenomena Preceding the Melting of Pure Metals and Alloys
Authors: Montanari Roberto , Varone Alessandra
Published: November 2016

Precursor phenomena of melting in pure metals (In, Pb, Bi and Sn) and alloys of the systems Pb-Bi and In-Sn with different compositions have been investigated by means of Mechanical Spectroscopy (MS), i.e. dynamic modulus and damping measurements.
MS tests evidenced that a sharp drop of dynamic modulus E takes place in a temperature range ΔT before the formation of the first liquid: the modulus variation ΔE and the corresponding temperature range ΔT depend on the specific metal or alloy.
The modulus drop is consistent with a relevant increase of interstitial concentration (self-interstitials assuming the dumbbell configuration), as predicted by the Granato’s theory of melting. The increase of damping in the same temperature range of modulus drop supports this explanation. Owing to their dumbbell configuration self-interstitials interact with the flexural vibration of samples and the periodic re-orientation under the external applied stress leads to energy loss and damping increase. The increase of self-interstitials has the effect to weaken interatomic bonds (modulus drop) and favours the collapse of crystal lattice (melting).
Unraveling the Age Hardening Response in U-Nb Alloys
Authors: Hackenberg R.E. , Hemphill G.M. , Forsyth R.T. , Papin P.A. , Kelly A.M. , Tucker T.J. , Aikin Jr. R.M. , Alexander D.J. , Lopez M.F. , Clarke A.J.
Published: November 2016

Complicating factors that have stymied understanding of uranium-niobium’s aging response are briefly reviewed, including (1) niobium inhomogeneity, (2) machining damage effects on tensile properties, (3) early-time transients of ductility increase, and (4) the variety of phase transformations. A simple Logistic-Arrhenius model was applied to predict yield and ultimate tensile strengths and tensile elongation of U-4Nb as a function of thermal age. Fits to each model yielded an apparent activation energy that was compared with phase transformation mechanisms.
Evaluation of Weldability of Titanium Alloy Ti-6Al-4V and Aluminum Alloy 6061 Produced by Electron Beam Welding
Authors: Havlík Petr , Kouřil Jan , Foret Rudolf , Dlouhy Ivo , Enzinger Norbert , Wiednig Christopher
Published: November 2016

Aluminum and titanium alloys are among the most important and the most frequently used construction materials due to their physical and mechanical properties. Especially in the automotive and aerospace industry these materials allow to reduce the weight of structure which leads to reducing fuel consumption and environment pollution. These materials are often used together which leads to problems with junction between these materials. In addition to the mechanical joints, there is an effort to produce quality welded joints. Series of works focused to welding of Al/Ti joints by conventional and nonconventional welding methods were published [1, 4, 5, 6, 7]. By reduction of dimensions of molten material is possible to reduce the amount of emerging intermetallic phases and welding defects. Electron beam welding appears as suitable method for welding Al/Ti joints because it allows production of very narrow welds. The benefit is also necessity to perform electron beam welding in vacuum which is required for decrease energy losses of incident beam and simultaneously prevents reaction of molten metal with ambient atmosphere. This paper is focused to determine of appropriate parameters for electron beam welding of heterogeneous welds of titanium alloy Ti-6Al-4V and aluminum alloy 6061. Metallographic evaluation, analysis of chemical and phase composition were performed on the test welds for purpose to describing present phases. On the selected welds was evaluated the influence of intermetallic phases on the mechanical properties. The obtained results will be used for further experiments focused to optimize the process of electron beam welding of Al/Ti alloys.
Combined Effects of Grain Boundary Convection and Migration in Dynamic Phase Transformations
Authors: Montheillet Frank , Piot David
Published: November 2016

During large strain deformation of polycrystals, grain or interphase boundaries are driven by the material flow, which is a convection movement. By contrast, upon static recrystallization or grain growth, their motion takes place with respect to matter, which is referred to as grain boundary or interphase migration. During hot working, where dynamic phase transformations commonly occur, convection and migration operate simultaneously. According to local geometrical (e.g., prescribed velocity field, grain boundary curvature) and physical (e.g., grain boundary mobility, dislocation densities) conditions, they can reinforce or oppose each other, but generally combine in more complex ways. The aim of this work is to analyze such effects on the basis of simple analytical approaches. The results suggest that second phase particles or grains dynamically generated (i.e., during straining) exhibit approximately equiaxed shapes.
Effects of Electric Current on the Microstructures and Mechanical Properties of Artificial Aged 6061 Alloy
Authors: He Li Zi , Wang Ping , Liu Jing , Cui Jian Zhong
Published: November 2016

The influences of electric current on the microstructures and mechanical properties of 6061 aluminum alloy were investigated by electric conductivity measurement, tensile test, scanning electron microscope and transmission electron microscope. When applying electric current both at solid solution and ageing treatment, the alloy has the highest peak strength, and the time to peak strength shortens by 12h. The electric current applying during either solid solution or ageing, increases the density and size of β'' phase.
Magnetic Shape Memory Effect in Ni-Mn-Ga Single Crystal
Authors: Heczko Oleg , Kopecký Vít , Drahokoupil Jan , Vronka Marek , Perevertov Oleksiy , Kopeček Jaromír
Published: November 2016

Magnetic shape memory effect is general name for several effects in which the most visible feature is huge strain induced by magnetic field. Magnetic field-induced structure reorientation (MIR) occurs due to motion of twin boundaries in single phase. As the magnetic field is a relatively weak force compared with mechanical stress, very high mobility of twin boundaries is crucial. Here we study the properties of martensite relevant for this effect using X-ray diffraction, optical and electron microscopy, magnetic observation and mechanical testing. In 10M modulated martensite, two types of mobile twin boundary (type I and type II) are observed with complex layered microstructures consisting of a hierarchy of twinning systems. We search for analogue with non-magnetic Cu-Ni-Al shape memory alloy.
Influence of Carbon Addition on Mechanical Properties of Thixomolded Magnesium Alloy
Authors: Hino Makoto , Hashimoto Yoshiaki , Murakami Koji , Mitooka Yutaka , Kanadani Teruto
Published: November 2016

For the purpose of application for structural members such as the automobile, effect of carbon modification to the AZ91D magnesium alloy chip surface on fatigue property was examined by the rotary bending test. The carbon modification to the chip surface was quite useful for the control of the internal defect for the thick part on the thixomolding process. The depression of the internal defect by the carbon nanoparticle modification is closely related to the improvement of flowability, and that is presumed to be based on promoting the filling of the molten metal into the metal die inside. The tensile strength and elongation were respectively improved by the carbon addition. In addition, the fatigue strength also improved over 15%. This improvement of the mechanical property is based on the refinement of the crystal grain as well as the depression of the internal defects.
Impact of Silicon, Magnesium and Strontium on Feeding Ability of AlSiMg Cast Alloys
Authors: Huber Gerhard , Djurdjevic Mile B. , Rafetzeder Michael
Published: November 2016

This paper shows how characteristic solidification temperatures, including rigidity temperature can be used to quantify the various feeding mechanisms that occur during solidification of AlSiMg alloys. In addition, the impact of Silicon, Magnesium and Strontium on the temperature intervals of various feeding regions have been analyzed.