International Journal of Minerals, Metallurgy and Materials

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A novel method for improving cerussite sulfidization

Qi-cheng Feng, Shu-ming Wen, Wen-juan Zhao, Qin-bo Cao, Chao Lü

2016, 23(6): 609-617. doi: 10.1007/s12613-016-1273-5

中文摘要(212) PDF(10) SpringerLink

摘要:
Evaluation of flotation behavior, solution measurements, and surface analyses were performed to investigate the effects of chloride ion addition on the sulfidization of cerussite in this study. Micro-flotation tests indicate that the addition of chloride ions prior to sulfidization can significantly increase the flotation recovery of cerussite, which is attributed to the formation of more lead sulfide species on the mineral surface. Solution measurement results suggest that the addition of chloride ions prior to sulfidization induces the transformation of more sulfide ions from pulp solution onto the mineral surface by the formation of more lead sulfide species. X-ray diffraction and energy-dispersive spectroscopy indicate that more lead sulfide species form on the mineral surface when chloride ions are added prior to sulfidization. These results demonstrate that the addition of chloride ions prior to sulfidization can significantly improve the sulfidization of cerussite, thereby enhancing the flotation performance.

Infiltration behavior of sintering liquid on nuclei ores during low-titanium ore sintering process

Dong-hui Liu, Jian-liang Zhang, Xun Xue, Guang-wei Wang, Ke-jiang Li, Zheng-jian Liu

2016, 23(6): 618-626. doi: 10.1007/s12613-016-1274-4

中文摘要(243) PDF(10) SpringerLink

摘要:
Sinter strength is dependent not only on the self-intensity of the residual rude and bonding phase but also on the bonding degree between them. The infiltration behavior of sintering liquid on nuclei ores influences the bonding degree, which ultimately determines the sinter strength. Infiltration tests were conducted using micro-sinter equipment. The infiltration area index of original liquid (IAO), infiltration volume index of secondary liquid (IVS), and sinter body bonding strength (SBS) were proposed to study the melt infiltration behavior. The results show that the IVS first increases and then decreases with increasing TiO₂ content in adhering fines, whereas the IAO exhibits the opposite behavior. Compared with the original liquid, the secondary liquid shows lower porosity, smaller pores, and more uniform distribution. The SBS increases first and then decreases with increasing IAO and TiO₂ content, and reaches a maximum when the IAO and TiO₂ contents are approximately 0.5 and 2.0wt%, respectively. The SBS first increases and then tends to be stable with increasing IVS. The TiO₂ content is suggested to be controlled to approximately 2.0wt% in low-titanium ore sintering.

Fluoride evaporation and crystallization behavior of CaF₂–CaO–Al₂O₃–(TiO₂) slag for electroslag remelting of Ti-containing steels

Cheng-bin Shi, Jung-wook Cho, Ding-li Zheng, Jing Li

2016, 23(6): 627-636. doi: 10.1007/s12613-016-1275-3

中文摘要(258) PDF(10) SpringerLink

摘要:
To elucidate the behavior of slag films in an electroslag remelting process, the fluoride evaporation and crystallization of CaF₂–CaO–Al₂O₃–(TiO₂) slags were studied using the single hot thermocouple technique. The crystallization mechanism of TiO₂-bearing slag was identified based on kinetic analysis. The fluoride evaporation and incubation time of crystallization in TiO₂-free slag are found to considerably decrease with decreasing isothermal temperature down to 1503 K. Fish-bone and flower-like CaO crystals precipitate in TiO₂-free slag melt, which is accompanied by CaF₂ evaporation from slag melt above 1503 K. Below 1503 K, only near-spherical CaF₂ crystals form with an incubation time of less than 1 s, and the crystallization is completed within 1 s. The addition of 8.1wt% TiO₂ largely prevents the fluoride evaporation from slag melt and promotes the slag crystallization. TiO₂ addition leads to the precipitation of needle-like perovskite (CaTiO₃) crystals instead of CaO crystals in the slag. The crystallization of perovskite (CaTiO₃) occurs by bulk nucleation and diffusion-controlled one-dimensional growth.

Development of inclusions in 3104 alloy melt during heating and holding treatments

Xiao-xiong Luo, Hai-tao Zhang, Xing Han, Shi-jie Guo, Dan-dan Chen, Jian-zhong Cui, Hiromi Nagaumi

2016, 23(6): 637-644. doi: 10.1007/s12613-016-1276-2

中文摘要(220) PDF(16) SpringerLink

摘要:
Developments in the contents of different typical inclusions in 3104 alloy melt were described during heating and holding processing. The settling process of inclusion particles was investigated by measuring the contents of inclusions in the surface, center, and bottom layers of the molten metal. In the results, main inclusions observed and determined by Prefil and PoDFA methods are MgO, Al₂O₃, spinel (MgAl₂O₄), and TiB₂ particles or thin films. It is found that some small particles of Al₂O₃ and MgO are transformed into spinel particles, and the formation rate increases as the temperature and the holding period of melt increase. The content of inclusions increases from 3.37 mm²·kg^-1 to 7.54 mm²·kg^-1 and then decreases to 3.08 mm²·kg^-1 after holding for 90 min. This is attributed to a settling phenomenon and a significant increase in settling velocity after holding for 60 min. The content of inclusion particles decreases by means of settlement and flotation in liquid aluminum with an increase in holding time. The theoretical analysis and experiment results are in essential agreement with those from industrial production.

Abrasive resistance of metastable V–Cr–Mn–Ni spheroidal carbide cast irons using the factorial design method

V. G. Efremenko, K. Shimizu, A. P. Cheiliakh, T. V. Pastukhova, Yu. G. Chabak, K. Kusumoto

2016, 23(6): 645-657. doi: 10.1007/s12613-016-1277-1

中文摘要(324) PDF(13) SpringerLink

摘要:
Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C–4wt%Mn–1.5wt%Ni spheroidal carbide cast irons with varying vanadium (5.0wt%–10.0wt%) and chromium (up to 9.0wt%) contents. The alloys were quenched at 920℃. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides (M₇C₃) and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%–10.0wt% for V and 2.5wt%–4.5wt% for Cr, which corresponds to the alloys containing 9vol%–15vol% spheroidal VC carbides, 8vol%–16vol% M₇C₃, and a metastable austenite/martensite matrix. The wear resistance is 1.9–2.3 times that of the traditional 12wt% V–13wt% Mn spheroidal carbide cast iron.

Influence of soaking time in deep cryogenic treatment on the microstructure and mechanical properties of low-alloy medium-carbon HY-TUF steel

Ahmad Zare, S. R. Hosseini

2016, 23(6): 658-666. doi: 10.1007/s12613-016-1278-0

中文摘要(302) PDF(8) SpringerLink

摘要:
The influence of soaking time in deep cryogenic treatment on the tensile and impact properties of low-alloy medium-carbon HY-TUF steel was investigated in this study. Microstructural studies based on phase distribution mapping by electron backscatter diffraction show that the deep cryogenic process causes a decrease in the content of retained austenite and an increase in the volume fraction of η-carbide with increasing soaking time up to 48 h. The decrease in the content of retained austenite from ~1.23vol% to 0.48vol% suggests an isothermal martensitic transformation at 77 K. The η-type precipitates formed in deep cryogenic-treated martensite over 48 h have the Hirotsu and Nagakura orientation relation with the martensitic matrix. Furthermore, a high coherency between η-carbide and the martensitic matrix is observed by high-resolution transmission electron microscopy. The variations in macrohardness, yield strength, ultimate tensile strength, and ductility with soaking time in the deep cryogenic process show a peak/plateau trend.

Effect of shot peening on hydrogen embrittlement of high strength steel

Xin-feng Li, Jin Zhang, Ming-ming Ma, Xiao-long Song

2016, 23(6): 667-675. doi: 10.1007/s12613-016-1279-z

中文摘要(476) PDF(41) SpringerLink

摘要:
The effect of shot peening (SP) on hydrogen embrittlement of high strength steel was investigated by electrochemical hydrogen charging, slow strain rate tensile tests, and hydrogen permeation tests. Microstructure observation, microhardness, and X-ray diffraction residual stress studies were also conducted on the steel. The results show that the shot peening specimens exhibit a higher resistance to hydrogen embrittlement in comparison with the no shot peening (NSP) specimens under the same hydrogen-charging current density. In addition, SP treatment sharply decreases the apparent hydrogen diffusivity and increases the subsurface hydrogen concentration. These findings are attributed to the changes in microstructure and compressive residual stress in the surface layer by SP. Scanning electron microscope fractographs reveal that the fracture surface of the NSP specimen exhibits the intergranular and quasi-cleavage mixed fracture modes, whereas the SP specimen shows only the quasi-cleavage fractures under the same hydrogen charging conditions, implying that the SP treatment delays the onset of intergranular fracture.

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

Hamid Sazegaran, Ali-Reza Kiani-Rashid, Jalil Vahdati Khaki

2016, 23(6): 676-682. doi: 10.1007/s12613-016-1280-6

中文摘要(281) PDF(7) SpringerLink

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

Preparation and tensile properties of DD5 single crystal castings

Xiang-feng Liang, Yu-tao Zhao, Zhi-hong Jia, Chi Zhang

2016, 23(6): 683-690. doi: 10.1007/s12613-016-1281-5

中文摘要(338) PDF(12) SpringerLink

摘要:
The preparation procedure of DD5 single crystal castings was optimized. The microstructure characteristics of DD5 single crystal superalloy were investigated by microstructure observation and segregation behavior examination. The results show that the grain orientation is optimized by constraining the spiral crystallizer in [001] orientation and spatial scale. Also, the γ’ phase of inter-dendrites is larger and more irregular than that in dendrite arms. High temperature tensile tests of DD5 single crystal castings exhibit that the peak stress increases with increasing temperature, while the area reduction shows an opposite trend, when the temperature is below 800℃; meanwhile, when the temperature is between 800℃ and 1000℃, the fracture stress of the alloy is the same as the peak stress. The fracture mode changes from shear to ductile with increasing temperature from 600℃ and 1000℃.

Influence of microstructure on the corrosion resistance of Fe–44Ni thin films

Lin Lu, Tian-cheng Liu, Xiao-gang Li

2016, 23(6): 691-697. doi: 10.1007/s12613-016-1282-4

中文摘要(288) PDF(8) SpringerLink

摘要:
An Fe–44Ni nanocrystalline (NC) alloy thin film was prepared through electrodeposition. The relation between the microstructure and corrosion behavior of the NC film was investigated using electrochemical methods and chemical analysis approaches. The results show that the NC film is composed of a face-centered cubic phase (γ-(Fe,Ni)) and a body-centered cubic phase (α-(Fe,Ni)) when it is annealed at temperatures less than 400℃. The corrosion resistance increases with the increase in grain size, and the corresponding corrosion process is controlled by oxygen reduction. The NC films annealed at 500℃ and 600℃ do not exhibit the same pattern, although their grain sizes are considerably large. This result is attributed to the existence of an anodic phase, Fe_0.947Ni_0.054, in these films. Under this condition, the related corrosion process is synthetically controlled by anodic dissolution and depolarization.

Fluorite Ce_0.8Sm_0.2O_2-δ porous layer coating to enhance the oxygen permeation behavior of a BaCo_0.7Fe_0.2Nb_0.1O_3-δ mixed conductor

Tai-he Wang, Wei-jia Song, Rong Li, Qiang Zhen

2016, 23(6): 698-703. doi: 10.1007/s12613-016-1283-3

中文摘要(278) PDF(7) SpringerLink

摘要:
Fluorite Ce_0.8Sm_0.2O_2-δ (SDC) nanopowder with a crystallite size of 15 nm was synthesized by a co-precipitation method. An SDC porous layer was coated onto a BaCo_0.7Fe_0.2Nb_0.1O_3-δ (BCFN) mixed conductor to improve its oxygen transport behavior. The results show that the SDC-coated BCFN membrane exhibits a remarkably higher oxygen permeation flux (J_O₂) than the uncoated BCFN in the partial oxidation of coke oven gas (COG). The maximum (J_O₂) value of the SDC-coated BCFN is 18.28 mL·min^-1·cm^-2 under a COG/air flux of 177 mL·min^-1/353 mL·min^-1 at 875℃ when the thickness of the BCFN membrane is 1 mm; this (J_O₂) value is 23% higher than that of the uncoated BCFN membrane. This enhancement is likely because of the higher oxygen ionic conductivity of SDC, which supplies oxygen vacancies and accelerates oxygen exchange on the membrane/coating layer/gas three-phase boundary.

La₂Zr₂O₇ TBCs toughened by Pt particles prepared by cathode plasma electrolytic deposition

Shun-jie Deng, Peng Wang, Ye-dong He, Jin Zhang

2016, 23(6): 704-715. doi: 10.1007/s12613-016-1284-2

中文摘要(239) PDF(8) SpringerLink

摘要:
La₂Zr₂O₇ thermal barrier coatings (TBCs) with dispersed Pt particles were prepared by cathode plasma electrolytic deposition (CPED) with ceramic balls added to the cathode region. Compared with the conventional CPED, when ceramic balls are used in the cathode region, the plasma discharge ignition current density decreases approximately 62-fold and the stable plasma discharges occur at the whole cathode surface. Such TBCs with a thickness of 100 μm exhibit a crack-free surface and are composed of pyrochlore-structured La₂Zr₂O₇. Cyclic oxidation, scratching, and thermal insulation capability tests show that such TBCs not only exhibit high resistance to oxidation and spallation but also provide good thermal insulation. These beneficial effects are attributed to the excellent properties of TBCs, such as good thermal insulation because of low thermal conductivity, high-temperature oxidation resistance because of low-oxygen diffusion rate, and good mechanical properties because of the toughening effect of Pt particles.

Effect of sintering on the relative density of Cr-coated diamond/Cu composites prepared by spark plasma sintering

Wei Cui, Hui Xu, Jian-hao Chen, Shu-bin Ren, Xin-bo He, Xuan-hui Qu

2016, 23(6): 716-722. doi: 10.1007/s12613-016-1285-1

中文摘要(318) PDF(12) SpringerLink

摘要:
Cr-coated diamond/Cu composites were prepared by spark plasma sintering. The effects of sintering pressure, sintering temperature, sintering duration, and Cu powder particle size on the relative density and thermal conductivity of the composites were investigated in this paper. The influence of these parameters on the properties and microstructures of the composites was also discussed. The results show that the relative density of Cr-coated diamond/Cu reaches ~100% when the composite is gradually compressed to 30 MPa during the heating process. The densification temperature increases from 880 to 915℃ when the diamond content is increased from 45vol% to 60vol%. The densification temperature does not increase further when the content reaches 65vol%. Cu powder particles in larger size are beneficial for increasing the relative density of the composite.

Graphene-reinforced aluminum matrix composites prepared by spark plasma sintering

Wen-ming Tian, Song-mei Li, Bo Wang, Xin Chen, Jian-hua Liu, Mei Yu

2016, 23(6): 723-729. doi: 10.1007/s12613-016-1286-0

中文摘要(633) PDF(50) SpringerLink

摘要:
Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering (SPS). The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide (Al₄C₃) is not formed during SPS processing. Further addition of graphene (above 1wt%) results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.

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2016年第23卷第6期