Showing papers in "Materials Transactions in 2018"

Factors Affecting Sand Solidification Using MICP with Pararhodobacter sp.

Abstract: Biomineralization is an environmentally friendly technology for improving soil-engineering properties. One of the most common biomineralization processes is microbially induced calcite precipitation (MICP). In this study, sand solidi cation tests were conducted using Pararhodobacter sp., which is a local ureolytic bacteria obtained from the sand near beach rock in Okinawa, Japan. The goal of this study was to solidify a specimen having an estimated uncon ned compressive strength (UCS) of more than several MPa to improve soil properties and investigate the in uence of various factors on the engineering properties of treated soil catalyzed by ureolytic bacteria (curing temperature, injection interval of cementation solution, Ca2+ concentration, curing time, bacterial population, re-injection of bacteria and particle size of sand). Model test specimens were cemented up to an estimated UCS of 10 MPa after 14 days under the following conditions: a curing temperature of 30°C, an injection interval of 1 day, and a Ca2+ concentrations in cementation solution of 0.5 M. Multiple regression analysis showed that the relevant conditions for estimating UCS were test period, D (days), and Ca2+ concentration of the cementation solution, Cca (M). The formula for predicting the estimated UCS (qeu (MPa)) was qeu = 13.99 Cca + 0.37 D − 0.09. Overall, the results of this study will contribute to the application of a new technique to sand improvement and bio-stimulation. [doi:10.2320/matertrans.M-M2017849]

Microstructure and Mechanical Properties of Mg–Gd–Y–Zn–Zr Alloy Prepared by Repetitive Upsetting and Extrusion

Abstract: The microstructure and room temperature tensile properties of Mg­12Gd­3Y­2Zn­0.5Zr (wt%) alloy processed by repetitive upsetting and extrusion (RUE) at decreasing temperature condition were investigated. The RUE was carried out up to cumulative strains of around 5.4 with decreasing temperature from 753 to 683K pass-by-pass. With increasing RUE passes, average grain size was gradually decreased from 58 to 7.3 μm and microstructure became more homogeneous. Block-shaped long period stacking ordered (LPSO) phases at grain boundary were broken into small blocks or rods. Lamellar LPSO structures dissolved gradually and ¢-Mg5(Gd,Y) phase particles precipitated at grain boundaries. Both strength and ductility were improved simultaneously with increasing RUE passes. After 4 RUE passes, the ultimate tensile strength, yield strength and elongation to failure of the alloy reached to 351MPa, 262MPa and 10.3%, respectively. The significant improvement of mechanical properties could be ascribed to grain refinement, dispersion of ¢-Mg5(Gd,Y) phase particles and redistribution of fragmented block-shaped LPSO phases. [doi:10.2320/matertrans.M2017323]

Recent Progress in Shape Memory Alloys

Abstract: In this paper, the progress on shape memory alloys (SMAs) for the past 10 years was reviewed and research trends in the eld were brie y introduced. Especially, basic properties in some novel alloys, such as the ductile Cu-Al-Mn SMA, ferrous superelastic alloys and NiMn-based metamagnetic SMAs are focused on and the superelastic behavior at cryogenic temperatures in some SMAs, such as TiNi and NiCo-Mn-In alloys, was introduced. [doi:10.2320/matertrans.M2017340]

Clinching of Similar and Dissimilar Sheet Materials of Galvanized Steel, Aluminium Alloy and Titanium Alloy

Abstract: Aimed to describe the clinching join-abilities of galvanized steel with aluminium alloy and titanium alloy, extensible die clinched joints were prepared for similar and dissimilar sheet materials combinations. The quality of the clinched joints was analysed from the aspects of material forming, load-bearing capacity and failure modes. The failure mechanism of the clinched joints was researched from macroscopic and microscopic aspects. The results show that the sheet materials which have better strength and hardness, are suitable to be used as upper sheets in the clinching process. [doi:10.2320/matertrans.M2017319]

New Mg–V–Cr BCC Alloys Synthesized by High-Pressure Torsion and Ball Milling

Abstract: 1Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka, Japan 2WPI, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka, Japan 3International Research Center for Hydrogen Energy, Kyushu University, Fukuoka, Japan 4Kyushu University Platform of Inter/Transdisciplinary Energy Research, Fukuoka, Japan 5Faculdade de Ciências Aplicadas, Universidade Estadual de Campinas (FCA-UNICAMP), Rua Pedro Zaccaria, 1300, CEP 13484-350, Limeira -SP, Brazil

Recent Progress in Research and Development of Metallic Structural Biomaterials with Mainly Focusing on Mechanical Biocompatibility

Abstract: The progress of metallic structural biomaterials, mainly titanium alloys, for implants with mainly focusing on mechanical biocompatibility is described. Mechanical biocompatibility includes not only Young’s modulus but also broad sense of mechanical biocompatibilities such as balance of strength and elongation, fatigue endurance (fatigue strength) and fracture toughness. Specially, the present paper focuses on developments of high fatigue strength of (α + β)-type titanium alloys composed of non-toxic elements, low Young’s modulus β-type titanium alloys composed of non-toxic and allergy-free elements, Young’s modulus self-adjustable β-type titanium alloys composed of non-toxic elements, Ni-free β-type titanium alloys for biomedical applications. Ni-free stainless steels and Co-Cr-Mo alloys, cell viability of pure metals, and some very recent research and development topics are also brie y introduced in the present paper. [doi:10.2320/matertrans.M2017180]

High-Strength Ti-Based Alloys Containing Fe as One of the Main Alloying Elements

Abstract: As well as the most of other 3d late transition metals Fe is a good ¢-Ti stabilizer, has a large solid solubility in ¢-Ti and owing to the atomic size difference with Ti can enable significant solution strengthening. The structure and mechanical properties of Ti alloys containing significant amount of Fe (or Fe together with Co, Cu and other elements) are reviewed in the present work. At high content of the late transition metals (for example, more than about 15 at% of Fe) the structure of these alloys consist of the rounded primary dendrites of an ordered cP2 intermetallic compound and an eutectic consisting of the cP2 intermetallic compound and a supersaturated cI2 ¢-Ti solid solution. cP2+cI2 phase Ti­Fe alloys, their derivatives: Ti­Fe­Co, Ti­Fe­Cu, etc+ , and cI2 ¢-Ti solid solution alloys containing Sn and Nb exhibit high compressive strength and plasticity. At lower Fe content a supersaturated ¢-Ti solid solution single phase structure is formed. However, these alloys also show good mechanical properties especially when alloyed with Sn and Nb. The structure and properties of various kinds of such alloys are discussed in the present paper. [doi:10.2320/matertrans.M2018114]

Age Heat Treatment of the CoCrFeNiTi0.3 High-Entropy Alloy

Abstract: The hardness and microstructure of an as-cast CoCrFeNiTi0.3 high-entropy alloy after age heat treatment 24­144 h at 500­1000°C are investigated. The as-cast alloy has a dendritic structure in which the dendrite is a Ti-lean face-centered cubic solid solution phase (FCC1) and the interdendrite consists of a Ti-rich face-centered cubic solid solution phase (FCC2), a mixture of (Cr, Fe)-rich · phase and (Ni, Ti)-rich © phase. After a 144 h of age heat treatment, age hardening is observed at temperatures of 600­800°C because the amount of · phase increases in the interdendrite. The optimum hardness is obtained at an aging temperature of 700°C, which makes the hardness increase from HV366 to HV508. However, age softening occurs at 900­1000°C. The vanishing · phase at 1000°C brings the alloy hardness to the minimum, HV223. [doi:10.2320/matertrans.M2017418]

Effects of Various Factors on Carbonate Particle Growth Using Ureolytic Bacteria

Abstract: In Microbially Induced Carbonate Precipitation (MICP), bacteria can perform metabolic activities that promote the deposition of carbonate particles in the form of calcite. Previously, purified urease and CaCl2 have been used for hydrolysis of urea to deposit carbonate particles. In our present study, Mg2+ ions were added to investigate the effect on the deposition of carbonate particles, because Mg2+ ions can delay the reaction rate and enhance the crystal deposition rate. Additionally, other parameters (temperature, solvent, bacterial population, and CaCl2 concentration) were taken into consideration to enhance the amount of carbonate deposition by ureolytic bacteria. The aim of this study was to investigate the mechanism of carbonate particle generation using urease producing bacteria (Pararhodobacter sp.) in laboratory test conditions using a translucent cell. In this study, marine ureolytic (Pararhodobacter sp.) bacteria were used and their urease activity was estimated considering bacterial concentration, temperature, and the effect of Ca2+ and Mg2+ ions. Digital microscopy analysis revealed the direct involvement of these parameters on the deposition of carbonate particles. The results of this study also showed that the type of deposited crystals, their shapes, and bacterial growth rate change depending on the medium used, the type of carbonate (metal ion used), CaCl2 concentration, and temperature. In addition, when Mg2+ and Ca2+ ions were used, the amount of particle deposition increased, which enhanced the possibility of becoming a superior binder for sand particles. This study is useful for the various sand solidification experiments and to regulate the most suitable conditions for engineering applications in future studies. [doi:10.2320/matertrans.M-M2018830]

Prediction of Fatigue Strength in Steels by Linear Regression and Neural Network

Abstract: This paper examines machine learning methods to predict fatigue strength with high accuracy using existing database. The fatigue database was automatically classified by hierarchical clustering method, and a group of carbon steels was selected as a target of machine learning. In linear regression analyses, a model selection was conducted from all possible combinations of explanatory variables based on cross validation technique. The derived linear regression model provided more accurate prediction than existing empirical rules. In neural network models, local and global sensitivity analyses were performed and the results of virtual experiments were consistent with existing knowledge in materials engineering. It demonstrated that the machine learning method provides prediction of fatigue performance with high accuracy and is one of promising method to accelerate material development. [doi:10.2320/matertrans.ME201714]

Dynamic Material Flow Analysis and Forecast of Copper in Global-Scale: Considering the Difference of Recovery Potential between Copper and Copper Alloy

Abstract: The recovery of copper (Cu) from secondary sources has received much attention because of its scarcity of natural resources. In this work, we estimated the input, in-use stock and discard of copper and copper alloy during 1950­2015 in global scale, and forecast them until 2050. In addition, we estimated the potential of scrap recovery for copper/copper alloys. It was estimated that the total amount of in-use stock of copper and copper alloy were 177,000 kt and 44,200 kt in 2015, respectively. The in-use stock, discard and input of copper in 2050 will reach 381,000­ 588,000 kt, 15,400­22,200 kt and 18,990­33,000 kt, respectively, whereas those for copper alloy will reach 77,500­134,000 kt, 3,020­4,680 kt and 3,760­7,200kt, respectively. The copper content in recoverable scraps of copper and copper alloy will reach 15,100­27,300 kt, and this accounts for 55.1­79.0% of copper content in annual input of copper and copper alloy in 2050. The range in forecast was caused by the difference in the saturation amount of in-use stock per capita and recovering rates of scraps. [doi:10.2320/matertrans.M2017399]

Influence of Cooling Rate on Primary Particle and Solute Distribution in High-Speed Twin-Roll Cast Al-Mn Based Alloy Strip

Abstract: Binary Al-Mn, ternary Al-Mn-Fe and Al-Mn-Si alloys were prepared by different cooling rates during solidi cation using direct chill-casting and high-speed twin-roll casting. Mn concentration and solute distribution in Al matrix were examined. The Mn concentration in solid solution was considered almost equivalent in as-cast condition. In contrast, much amount of decomposition of supersaturated Mn in solid solution occurred in high-speed twin-roll cast alloys after homogenization. In high-speed twin-roll cast strips, ne distribution of constituent particles in Al-Mn-Fe alloy and homogeneous solute distribution in Al matrix in Al-Mn-Si alloy were obtained due to the high cooling rate of the high-speed twin-roll casting. After homogenization treatment, coarsening and spheroidization of the constituent particles were mainly observed in Al-Mn-Fe alloy, while formation of ne dispersoids was predominantly observed in Al-Mn-Si alloy. Such differences in microstructure resulted from the decomposition behavior of supersaturated Mn in solid solution. [doi:10.2320/matertrans.F-M2017843]

Deformation Microstructure Developed by Nanoindentation of a MAX Phase Ti2AlC

Abstract: Deformation microstructure that developed during nanoindentation of a MAX phase Ti2AlC was characterized by the scanning probe microscopy and the transmission electron microscopy. To investigate the plastic anisotropy, nanoindentation measurements were made on grains with the normal parallel to h33 62i, h0001i, and h11 20i. The basal slip, f0001gh11 20i, was found to be predominant as the deformation mechanism for all the indentation directions. It was also indicated that, upon nanoindentation along h0001i and h11 20i, non-basal slips occurred underneath the indenter. The slip system of the non-basal dislocations was identified to be ð 12 16Þ1⁄21 211 by analyzing the dislocations. Furthermore, fine-scaled kink-bands were found to form underneath the residual impression. The formation of the kink-band was accompanied by delamination, i.e., micro-cracking along the basal plane, suggesting that the delamination plays an important role for kink-band formation in Ti2AlC. [doi:10.2320/matertrans.MBW201703]

First-Principles Study of BCC/FCC Phase Transition Promoted by Interstitial Carbon in Iron

Abstract: 1Institute for NanoScience Design, Osaka University, Toyonaka 560-8531, Japan 2Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan 3Division of Mechanical Engineering, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan 4Nanotechnology Program, Vietnam-Japan University, Luu Huu Phuoc Street, My Dinh 1 Ward, Nam Tu Liem District, Ha Noi, Viet Nam

Effective Alloying Treatment for Platinum Using Iron Chloride Vapor

Abstract: An effective alloying treatment for Pt using FeClx (x = 2, 3) vapor was demonstrated towards developing a novel recovery process for platinum group metals (PGMs) in catalyst scrap. Suitable reaction conditions were discussed from the perspective of thermodynamics, and its validity was con rmed experimentally. When pure Pt samples were reacted with FeCl2 vapor at 1200 K under the coexistence of metallic Fe, an Fe-Pt alloy showing ferromagnetism was easily formed, even though the samples were not in physical contact with the metallic Fe. On the basis of thermodynamic considerations, alloying of Pt mainly proceeds via the disproportionation of FeCl2 vapor, with the gaseous phase containing FeClx acting as the medium to transport Fe from the metallic Fe to the Pt samples. When the alloyed sample was kept under FeCl3 vapor at 1200 K, Fe was removed and ferromagnetism was lost. Therefore, it is concluded that FeCl2 vapor treatment under the coexistence of Fe is a feasible and useful technique for alloying Pt and forming a ferromagnetic Fe-Pt alloy. The results obtained in this study indicate that treatment with FeCl2 vapor followed by magnetic separation has potential as an effective technique for concentrating PGMs directly from catalyst scrap. [doi:10.2320/matertrans.M-M2017844]

Preparation of Copper-Based Superhydrophobic Surfaces by Jet-Electrodeposition

Abstract: The surface state of metallic materials significantly affect their physical, chemical, and corrosion behavior. In the present study, superhydrophobic coating with copper deposits fabricated using a jet-electrodeposition device on the pure copper substrates for reducing the corrosion rate of the copper substrates was studied. The effect of the micro-nano structured superhydrophobic coating on the improvement of corrosion resistance was investigated. Factors including the microstructures and wetting properties of coating were comprehensively analyzed using a scanning electron microscope, a Fourier transformed infrared and a surface contact angle meter. Results showed that the superhydrophobic coatings demonstrated a micro-nanostructure on the copper substrates. After modifying the copper deposits with stearic acid, a superhydrophobic surface was consequently obtained. The static contact angle (CA) and the sliding angle of the copper-based superhydrophobic surface were 151.6° and 5.7°, respectively. The samples covered with superhydrophobic coating exhibited relatively higher corrosion potential and lower corrosion current than the bared pure copper samples, indicating a notable enhancement of corrosion resistance characterized using polarization tests by an electrochemical workstation. [doi:10.2320/matertrans.M2017361]

Preparation and Compressive Performance of an A356 Matrix Syntactic Foam

Abstract: The uniformity of the cell size of aluminum foams prepared by traditional melt foaming and gas injection methods is difficult to control. In order to improve the controllability of cell size and mechanical performance of aluminum foam, an A356 matrix syntactic foam was prepared by the improved stir casting process. Moreover, the compressive property of the syntactic foam was studied and compared with other metal foams. Al2O3 hollow spheres with the diameters of 3­5mm were added in the molten A356 alloy, then the syntactic foam can be obtained after stirring and compaction. The hollow spheres in the syntactic foam are random loose packed. The volume fraction of 3­3.5mm hollow spheres in the syntactic foam could reach to 56%. The total densities of the syntactic foams are around 1.79 g/cm3. Through the analysis both in macroscopic and microscopic, the interfacial bonding between aluminum matrix and hollow spheres was proved to be good even after mechanical cutting. The quasi-static compression result showed that the plateau stress of the syntactic foam with 3­3.5mm hollow spheres could reach up to 46MPa, and the corresponding densification strain energy is 20MJ/m3. Moreover, the plateau region is flat, long and relatively high. The syntactic foam with the hollow spheres of 3­4mm diameter has the highest overall porosity and the best compressive performance. Compared with other traditional aluminum foams, this syntactic foam has advantages in energy absorption performance and the adjustability of cell size. [doi:10.2320/matertrans.M2018003]