International Journal of Minerals, Metallurgy and Materials

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Dolochar as a reductant in the reduction roasting of iron ore slimes

2017, 24(12): 1341-1351. doi: 10.1007/s12613-017-1526-y

中文摘要(663) PDF(26) SpringerLink

摘要:
The present investigation examines the viability of dolochar, a sponge iron industry waste material, as a reductant in the reduction roasting of iron ore slimes, which are another waste generated by iron ore beneficiation plants. Under statistically determined optimum conditions, which include a temperature of 900℃, a reductant-to-feed mass ratio of 0.35, and a reduction time of 30-45 min, the roasted mass, after being subjected to low-intensity magnetic separation, yielded an iron ore concentrate of approximately 64wt% Fe at a mass recovery of approximately 71% from the feed iron ore slime assaying 56.2wt% Fe. X-ray diffraction analyses indicated that the magnetic products contain magnetite and hematite as the major phases, whereas the nonmagnetic fractions contain quartz and hematite.

研究论文

Recovery of valuable metals from waste diamond cutters through ammonia-ammonium sulfate leaching

Ping Xue, Guang-qiang Li, Yong-xiang Yang, Qin-wei Qin, Ming-xing Wei

2017, 24(12): 1352-1360. doi: 10.1007/s12613-017-1527-x

中文摘要(538) PDF(38) SpringerLink

摘要:
Copper and zinc were recovered from waste diamond cutters through leaching with an ammonia-ammonium sulfate system and air as an oxidant. The effects of experimental parameters on the leaching process were investigated, and the potential-pH (E-pH) diagrams of Cu-NH₃-SO₄^2--H₂O and Zn-NH₃-SO₄^2--H₂O at 25℃ were drawn. Results showed that the optimal parameters for the leaching reaction are as follows:reaction temperature, 45℃; leaching duration, 3 h; liquid-to-solid ratio, 50:1 (mL/g); stirring speed, 200 r/min; ammonia concentration, 4.0 mol/L; ammonium sulfate concentration, 1.0 mol/L; and air flow rate, 0.2 L/min. The results of the kinetics study indicated that the leaching is controlled by the surface chemical reaction at temperatures below 35℃, and the leaching is controlled by diffusion through the product layer at temperatures above 35℃.

研究论文

Decomposition mechanism of chromite in sulfuric acid-dichromic acid solution

Qing Zhao, Cheng-jun Liu, Bao-kuan Li, Mao-fa Jiang

2017, 24(12): 1361-1369. doi: 10.1007/s12613-017-1528-9

中文摘要(485) PDF(15) SpringerLink

摘要:
The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly understood. In this work, binary spinels of Mg-Al, Mg-Fe, and Mg-Cr in the powdered and lump states were synthesized and used as raw materials to investigate the decomposition mechanism of chromite in sulfuric acid-dichromic acid solution. The leaching yields of metallic elements and the changes in morphology of the spinel were studied. The experimental results showed that the three spinels were stable in sulfuric acid solution and that dichromic acid had little influence on the decomposition behavior of the Mg-Al spinel and Mg-Fe spinel because Mg²⁺, Al³⁺, and Fe³⁺ in spinels cannot be oxidized by Cr⁶⁺. However, in the case of the Mg-Cr spinel, dichromic acid substantially promoted the decomposition efficiency and functioned as a catalyst. The decomposition mechanism of chromite in sulfuric acid-dichromic acid solution was illustrated on the basis of the findings of this study.

研究论文Open Access

Cleanliness of Ti-bearing Al-killed ultra-low-carbon steel during different heating processes

Jian-long Guo, Yan-ping Bao, Min Wang

2017, 24(12): 1370-1378. doi: 10.1007/s12613-017-1529-8

中文摘要(538) PDF(16) SpringerLink

摘要:
During the production of Ti-bearing Al-killed ultra-low-carbon (ULC) steel, two different heating processes were used when the converter tapping temperature or the molten steel temperature in the Ruhrstahl-Heraeus (RH) process was low:heating by Al addition during the RH decarburization process and final deoxidation at the end of the RH decarburization process (process-I), and increasing the oxygen content at the end of RH decarburization, heating and final deoxidation by one-time Al addition (process-Ⅱ). Temperature increases of 10℃ by different processes were studied; the results showed that the two heating processes could achieve the same heating effect. The T.[O] content in the slab and the refining process was better controlled by process-I than by process-Ⅱ. Statistical analysis of inclusions showed that the numbers of inclusions in the slab obtained by process-I were substantially less than those in the slab obtained by process-Ⅱ. For process-I, the Al₂O₃ inclusions produced by Al added to induce heating were substantially removed at the end of decarburization. The amounts of inclusions were substantially greater for process-Ⅱ than for process-I at different refining stages because of the higher dissolved oxygen concentration in process-Ⅱ. Industrial test results showed that process-I was more beneficial for improving the cleanliness of molten steel.

研究论文

Effect of hot-dip galvanizing processes on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel

Chun-fu Kuang, Zhi-wang Zheng, Min-li Wang, Quan Xu, Shen-gen Zhang

2017, 24(12): 1379-1383. doi: 10.1007/s12613-017-1530-2

中文摘要(572) PDF(19) SpringerLink

摘要:
A C-Mn dual-phase steel was soaked at 800℃ for 90 s and then either rapidly cooled to 450℃ and held for 30 s (process A) or rapidly cooled to 350℃ and then reheated to 450℃ (process B) to simulate the hot-dip galvanizing process. The influence of the hot-dip galvanizing process on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel (DP600) was investigated using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile tests. The results showed that, in the case of process A, the microstructure of DP600 was composed of ferrite, martensite, and a small amount of bainite. The granular bainite was formed in the hot-dip galvanizing stage, and martensite islands were formed in the final cooling stage after hot-dip galvanizing. By contrast, in the case of process B, the microstructure of the DP600 was composed of ferrite, martensite, bainite, and cementite. In addition, compared with the yield strength (YS) of the DP600 annealed by process A, that for the DP600 annealed by process B increased by approximately 50 MPa because of the tempering of the martensite formed during rapid cooling. The work-hardening coefficient (n value) of the DP600 steel annealed by process B clearly decreased because the increase of the YS affected the computation result for the n value. However, the ultimate tensile strength (UTS) and elongation (A₈₀) of the DP600 annealed by process B exhibited less variation compared with those of the DP600 annealed by process A. Therefore, DP600 with excellent comprehensive mechanical properties (YS=362 MPa, UTS=638 MPa, A₈₀=24.3%, n=0.17) was obtained via process A.

研究论文

Effect of weld line positions on the tensile deformation of two-component metal injection moulding

Anchalee Manonukul, Sukrit Songkuea, Pongporn Moonchaleanporn, Makiko Tange

2017, 24(12): 1384-1393. doi: 10.1007/s12613-017-1531-1

中文摘要(516) PDF(30) SpringerLink

摘要:
Knowledge of the mechanical properties of two-component parts is critical for engineering functionally graded components. In this study, mono-and two-component tensile test specimens were metal injection moulded. Three different weld line positions were generated in the two-component specimens. Linear shrinkage of the two-component specimens was greater than that of the mono-component specimens because the incompatibility of sintering shrinkage of both materials causes biaxial stresses and enhances sintering. The mechanical properties of 316L stainless steel were affected by the addition of a coloured pigment used to identify the weld line position after injection moulding. For the two-component specimens, the yield stress and ultimate tensile stress were similar to those of 316L stainless steel. Because 316L and 630 (also known as 17-4PH) stainless steels were well-sintered at the interface, the mechanical properties of the weaker material (316L stainless steel) were dominant. However, the elongations of the two-component specimens were lower than those of the mono-component specimens. An interfacial zone with a microstructure that differed from those of the mono-material specimens was observed; its different microstructure was attributed to the gradual diffusion of nickel and copper.

研究论文

Tribological behavior of CrN-coated Cr-Mo-V steels used as die materials

Gülşah Aktaş Çelik, Şeyda Polat, Ş. Hakan Atapek

2017, 24(12): 1394-1402. doi: 10.1007/s12613-017-1532-0

中文摘要(485) PDF(9) SpringerLink

摘要:
DIN 1.2343 and 1.2367 steels are commonly used as die materials in aluminum extrusion, and single/duplex/multi-coatings enhance their surface properties. The design of an appropriate substrate/coating system is important for improving the tribological performance of these steels under service conditions because the load-carrying capacity of the system can be increased by decreasing the plastic deformation of the substrate. In this study, the tribological behavior of CrN-coated Cr-Mo-V steels (DIN 1.2343, 1.2367, and 1.2999 grades) was investigated using different setups and tribological pairs at room and elevated temperatures. The aim of this study was to reveal the wear resistance of a suggested system (1.2999/CrN) not yet studied and to understand both the wear and the failure characteristics of coated systems. The results showed that (i) among the steels studied, the DIN 1.2999 grade steel exhibited the lowest friction coefficient because it had the highest load-carrying capacity as a result of secondary hardening at elevated temperatures; (ii) at room temperature, both abrasive tracks and adhesive layers were observed on the worn surfaces; and (iii) a combination of chemical reactions and progressive oxidation caused aluminum adhesion on the worn surface, and the detachment of droplets and microcracking were the characteristic damage mechanisms at high temperatures.

研究论文

Reinforcing effect of graphene on the mechanical properties of Al₂O₃/TiC ceramics

Zuo-li Li, Jun Zhao, Jia-lin Sun, Feng Gong, Xiu-ying Ni

2017, 24(12): 1403-1411. doi: 10.1007/s12613-017-1533-z

中文摘要(462) PDF(12) SpringerLink

摘要:
Multilayer graphene (MLG)-reinforced Al₂O₃/TiC ceramics were fabricated through hot pressing sintering, and the reinforcing effect of MLG on the microstructure and mechanical properties of the composites was investigated by experiment and simulation. The simulation of dynamic crack initiation and propagation was investigated based on the cohesive zone method. The results show that the composite added with 0.2wt% MLG has excellent flexural strength and high fracture toughness. The major reinforcing mechanisms are the synergistic effect by strong and weak bonding interfaces, MLG pull-out, and grain refinement resulting from the addition of MLG. In addition, the aggravating of crack deflection, branching, blunting, and bridging have indispensable contribution to the improvement of the as-designed materials.

研究论文Open Access

Interfacial microstructure and mechanical properties of Ti-6Al-4V/Al7050 joints fabricated using the insert molding method

Hong-xiang Li, Xin-yu Nie, Zan-bing He, Kang-ning Zhao, Qiang Du, Ji-shan Zhang, Lin-zhong Zhuang

2017, 24(12): 1412-1423. doi: 10.1007/s12613-017-1534-y

中文摘要(466) PDF(12) SpringerLink

摘要:
Ti-6Al-4V/Al7050 joints were fabricated by a method of insert molding and corresponding interfacial microstructure and mechanical properties were investigated. The interfacial thickness was sensitive to holding temperature during the first stage, and a good metallurgical bonding interface with a thickness of about 90 μm can be obtained at 750℃. X-ray diffraction, transmission electron microscopy, and thermodynamic analyses showed that the interface mainly contained intermetallic compound TiAl₃ and Al matrix. The joints featured good mechanical properties, i.e., shear strength of 154 MPa, tensile strength of 215 MPa, and compressive strength of 283 MPa, which are superior to those of joints fabricated by other methods. Coherent boundaries between Al/TiAl₃ and TiAl₃/Ti were confirmed to contribute to outstanding interfacial mechanical properties and also explained constant fracture occurrence in the Al matrix. Follow-up studies should focus on improving mechanical properties of the Al matrix by deformation and heat treatment.

研究论文

Optical characterization of single-crystal diamond grown by DC arc plasma jet CVD

Li-fu Hei, Yun Zhao, Jun-jun Wei, Jin-long Liu, Cheng-ming Li, Fan-xiu Lü

2017, 24(12): 1424-1430. doi: 10.1007/s12613-017-1535-x

中文摘要(504) PDF(11) SpringerLink

摘要:
Optical centers of single-crystal diamond grown by DC arc plasma jet chemical vapor deposition (CVD) were examined using a low-temperature photoluminescence (PL) technique. The results show that most of the nitrogen-vacancy (NV) complexes are present as NV-centers, although some H2 and H3 centers and B-aggregates are also present in the single-crystal diamond because of nitrogen aggregation resulting from high N₂ incorporation and the high mobility of vacancies under growth temperatures of 950-1000℃. Furthermore, emissions of radiation-induced defects were also detected at 389, 467.5, 550, and 588.6 nm in the PL spectra. The reason for the formation of these radiation-induced defects is not clear. Although a Ni-based alloy was used during the diamond growth, Ni-related emissions were not detected in the PL spectra. In addition, the silicon-vacancy (Si-V)-related emission line at 737 nm, which has been observed in the spectra of many previously reported microwave plasma chemical vapor deposition (MPCVD) synthetic diamonds, was absent in the PL spectra of the single-crystal diamond prepared in this work. The high density of NV^- centers, along with the absence of Ni-related defects and Si-V centers, makes the single-crystal diamond grown by DC arc plasma jet CVD a promising material for applications in quantum computing.

研究论文Open Access

Microstructure and mechanical properties of a hot-extruded Al-based composite reinforced with core-shell-structured Ti/Al₃Ti

Li Zhang, Bao-lin Wu, Yu-lin Liu

2017, 24(12): 1431-1437. doi: 10.1007/s12613-017-1536-9

中文摘要(500) PDF(10) SpringerLink

摘要:
An Al-based composite reinforced with core-shell-structured Ti/Al₃Ti was fabricated through a powder metallurgy route followed by hot extrusion and was found to exhibit promising mechanical properties. The ultimate tensile strength and elongation of the composite sintered at 620℃ for 5h and extruded at a mass ratio of 12.75:1 reached 304 MPa and 14%, respectively, and its compressive deformation reached 60%. The promising mechanical properties are due to the core-shell-structured reinforcement, which is mainly composed of Al₃Ti and Ti and is bonded strongly with the Al matrix, and to the reduced crack sensitivity of Al₃Ti. The refined grains after hot extrusion also contribute to the mechanical properties of this composite. The mechanical properties might be further improved through regulating the relative thickness of Al-Ti intermetallics and Ti metal layers by adjusting the sintering time and the subsequent extrusion process.

研究论文

Influence of sintering temperature on the phases and photoelectric characteristics of BiOCl/ZnO composite powders

Song Chen, De-gui Zhu

2017, 24(12): 1438-1447. doi: 10.1007/s12613-017-1537-8

中文摘要(401) PDF(8) SpringerLink

摘要:
Zinc oxide is a typical functional oxide that has been widely researched for various industry applications due to its peculiar physical characteristics. However, to achieve its potential in promising applications, much work has been diligently performed to improve the physical properties of ZnO. In this work, an aqueous suspension route was used to prepare BiOCl/ZnO composite powders, and sintering processes were applied to investigate the influence of sintering temperature on the phase evolutions, microstructures, and photoelectric characteristics of BiOCl/ZnO composite powders. The results indicated that the photoelectric properties mainly depend on the relevant content of BiOCl in the composite powders and the sintering temperature. The photoelectric measurements in K₂SO₄ solutions show that the photoelectric properties of the samples with the appropriate BiOCl content (0.3mol% and 2.0mol%) are better than those of ZnO and commercial TiO₂ (P₂₅) powders, but the photoelectric measurements in NaOH solutions indicate that the photoelectric characteristics of the as-sintered samples are only better than those of P₂₅.

研究论文

Diffusion mechanism in molten salt baths during the production of carbide coatings via thermal reactive diffusion

Aliakbar Ghadi, Hassan Saghafian, Mansour Soltanieh, Zhi-gang Yang

2017, 24(12): 1448-1458. doi: 10.1007/s12613-017-1538-7

中文摘要(542) PDF(10) SpringerLink

摘要:
The diffusion mechanism of carbide-forming elements from a molten salt bath to a substrate surface was studied in this research, with particular focus on the processes occurring in the molten bath at the time of coating. Metal, oxide, and metal-oxide baths were investigated, and the coating process was performed on H13 steel substrates. Scanning electron microscopy and electron-probe microanalysis were used to study the coated samples and the quenched salt bath. The thickness of the carbide coating layer was 6.5 ±0.5, 5.2 ±0.5, or 5.7 ±0.5 μm depending on whether it was deposited in a metal, oxide, or metal-oxide bath, respectively. The phase distribution of vanadium-rich regions was 63%, 57%, and 74% of the total coating deposited in metal, oxide, and metal-oxide baths, respectively. The results obtained using the metal bath indicated that undissolved suspended metal particles deposited onto the substrate surface. Then, carbon subsequently diffused to the substrate surface and reacted with the metal particles to form the carbides. In the oxide bath, oxide powders dissolved in the bath with or without binding to the oxidative structure (Na₂O) of borax; they were then reduced by aluminum and converted into metal particles. We concluded that, in the metal and oxide baths, the deposition of metal particles onto the sample surface is an important step in the formation of the coating.

研究论文

Peculiarity of magnetoresistance of discontinuous ferromagnetic thin films

Yu. O. Shkurdoda, I. M. Pazukha, A. M. Chornous

2017, 24(12): 1459-1463. doi: 10.1007/s12613-017-1539-6

中文摘要(401) PDF(9) SpringerLink

摘要:
The magnetoresistive properties of discontinuous ferromagnetic Fe and Co thin films deposited by electron-beam sputtering onto glass substrates at room temperature were investigated. Tunnel magnetoresistance (MR) was observed for all of the as-deposited samples. The maximum MR was observed for Fe thin films with an effective thickness of 17 nm. In the case of the Co thin films, the annealing process led to a change of the type of MR to anisotropic at Co film thicknesses (d_Co) of 15 ≤ d_Co ≤ 25 nm and to positive isotropic at thicknesses of d_Co < 15 nm. By contrast, the MR type of Fe thin films did not change.

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2017年第24卷第12期