International Journal of Minerals, Metallurgy and Materials

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Segmentation algorithm of complex ore images based on templates transformation and reconstruction

2011, 18(4): 385-389. doi: 10.1007/s12613-011-0451-8

中文摘要(421) PDF(16) SpringerLink

摘要:
Lots of noises and heterogeneous objects with various sizes coexist in a complex image, such as an ore image; the classical image thresholding method cannot effectively distinguish between ores. To segment ore objects with various sizes simultaneously, two adaptive windows in the image were chosen for each pixel; the gray value of windows was calculated by Otsu’s threshold method. To extract the object skeleton, the definition principle of distance transformation templates was proposed. The ores linked together in a binary image were separated by distance transformation and gray reconstruction. The seed region of each object was picked up from the local maximum gray region of the reconstruction image. Starting from these seed regions, the watershed method was used to segment ore object effectively. The proposed algorithm marks and segments most objects from complex images precisely.

NO_x reduction by coupling combustion with recycling flue gas in iron ore sintering process

Yan-guang Chen, Zhan-cheng Guo, Gen-sheng Feng

2011, 18(4): 390-396. doi: 10.1007/s12613-011-0452-7

中文摘要(361) PDF(9) SpringerLink

摘要:
A new process called ‘NO_x reduction by coupling combustion with recycling flue gas (RCCRF)’ was proposed to decrease NO_x emission during the iron ore sintering process. The simulation test of NO_x reduction was performed over sintered ore and in the process of coke combustion. Experimentally, NO_x reduction was also carried out by sintering pot test. For sintered ore, the amount of NO_x emission is reduced by 15wt%–25wt% at 400–550℃ using 2.0vol% H₂ or 2.0vol% CO, or reduced by 10wt%–30wt% at 560–720℃ using 0.15vol% NH₃. NO_x reduction is around 10wt% by coupling combustion of pyrolysis gas and coke, or around 16wt% by recycling flue gas into coke combustion. By RCCRF, the maximum NO_x reduction ratio is about 23wt% in coke combustion experiment and over 40wt% in sintering pot test.

Analysis of three-dimensional vortexes below the free surface in a continuous casting mold

Cesar A. Real-Ramirez, Jesus I. Gonzalez-Trejo

2011, 18(4): 397-406. doi: 10.1007/s12613-011-0453-6

中文摘要(297) PDF(9) SpringerLink

摘要:
To study fluctuations of the free surface of liquid steel in the mold, two different models with the same casting conditions but different thicknesses were employed to analyze the hydrodynamic behavior at the top of the mold. The first model was a standard thickness slab, and the second had a thickness three times wider. It is found with the second model that above the plane formed by the steel jets, it is possible to observe four three-dimensional vortexes that interact with the submerged entry nozzle (SEN) and mold walls. By using a biphasic model to simulate the interface between the liquid and air inside the mold, the flow asymmetry and the fluctuations of the free surface can be clearly observed.

High-temperature properties and microstructure of Mo microalloyed ultra-high-strength steel

Qi-hang Han, Yong-lin Kang, Xian-meng Zhao, Lu-feng Gao, Xue-song Qiu

2011, 18(4): 407-412. doi: 10.1007/s12613-011-0454-5

中文摘要(267) PDF(11) SpringerLink

摘要:
The high-temperature mechanical properties and microstructure of forging billets of C-Si-Mn-Cr and C-Si-Mn-Cr-Mo ultra-high-strength cold-rolled steels (tensile strength≥1000 MPa, elongation≥10%) were studied. Through the comparison of reduction in area and hot deformation resistance at 600–1300℃, the Mo-containing steel was found to possess a higher strength and a better plasticity than the Mo-free one. The equilibrium phase diagram and atom fraction of Mo in different phases at different temperatures were calculated by Thermo-Calc software (TCW). The results analyzed by using transmission electron microscopy and TCW show that precipitates in the Mo-containing steel are primarily M₂₃C₆, which promote pearlite formation. The experimental data also show that a lower ductility point existing in the Mo-free steel at 850℃ is eliminated in the Mo-containing one. This is mainly due to the segregation of Mo at grain boundaries investigated by electron probe microanalysis (EPMA), which improves the strength of grain boundaries.

Inhibitive effect of Xylopia ferruginea extract on the corrosion of mild steel in 1M HCl medium

Pandian Bothi Raja, Afidah Abdul Rahim, Hasnah Osman, Khalijah Awang

2011, 18(4): 413-418. doi: 10.1007/s12613-011-0455-4

中文摘要(318) PDF(8) SpringerLink

摘要:
The alkaloid content of the leaves and stem bark of Xylopia ferruginea plant was isolated and tested for its anticorrosion potential on mild steel corrosion in a hydrochloric acid medium by using electrochemical impedance spectroscopy, potentiodynamic polarization measurement, scanning electron microscopy (SEM), and Fourier transform infra red (FTIR) analysis. The experimental results reveal the effective anticorrosion potential of the plant extract. The mixed mode of action exhibited by the plant extract is evidenced from the polarization study. SEM images proof the formation of a protective layer over the mild steel surface, and this is supported by the FTIR study. The possible mode of the corrosion inhibition mechanism has also been discussed.

Microstructure and embrittlement of the fine-grained heat-affected zone of ASTM4130 steel

Li-ying Li, Yong Wang, Tao Han, Chao-wen Li

2011, 18(4): 419-423. doi: 10.1007/s12613-011-0456-3

中文摘要(303) PDF(10) SpringerLink

摘要:
The mechanical properties and microstructure features of the fine-grained heat-affected zone (FGHAZ) of ASTM4130 steel was investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and welding thermal simulation test. It is found that serious embrittlement occurs in the FGHAZ with an 81.37% decrease of toughness, compared with that of the base metal. Microstructure analysis reveals that the FGHAZ is mainly composed of acicular, equiaxed ferrite, granular ferrite, martensite, and martensite-austenite (M-A) constituent. The FGHAZ embrittlement is mainly induced by granular ferrite because of carbides located at its boundaries and sub-boundaries. Meanwhile, the existence of martensite and M-A constituent, which distribute in a discontinuous network, is also detrimental to the mechanical properties.

Mechanism of Ag and Al on improving the glass forming ability of CuZr-based alloys

Xiao-dong Ni, Zheng Wang, Xiang Sun, Jiang Shen, Nan-xian Chen

2011, 18(4): 424-429. doi: 10.1007/s12613-011-0457-2

中文摘要(224) PDF(8) SpringerLink

摘要:
By a mean field theoretical computation, the equilibrium distributions of additional Ag and Al in the crystalline phase of CuZr-based alloys were determined to occupy the two sublattices of the B2 structure randomly. With the molecular dynamics technique, the effects of Ag and Al on the enthalpy difference (ΔH) between the supercooled melt and the crystalline phase were evaluated. The improved glass forming ability of Cu₄₅Zr₄₅Al₁₀and Cu₄₅Zr₄₅Ag₁₀ can be attributed to their remarkably smaller ΔH than that of CuZr. The calculated diffusion coefficients are more sensitive to the atomic weight of the component atoms than to their interaction strength. As the component atom with the largest mass, the additional Ag increases the viscosity of the supercooled melt significantly and the experimentally stronger glass formation ability of Cu₄₅Zr₄₅Ag₁₀ than Cu₄₅Zr₄₅Al₁₀ can be well understood.

Effects of aging on the microstructure of a Cu-Al-Ni-Mn shape memory alloy

U. Sari, T. Kirindi, F. Ozcan, M. Dikici

2011, 18(4): 430-436. doi: 10.1007/s12613-011-0458-1

中文摘要(319) PDF(13) SpringerLink

摘要:
The influence of aging on the microstructure and mechanical properties of Cu-11.6wt%Al-3.9wt%Ni-2.5wt%Mn shape memory alloy (SMA) was studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometer, and differential scanning calorimeter (DSC). Experimental results show that bainite, γ_2, and α phase precipitates occur with the aging effect in the alloy. After aging at 300dgC, the bainitic precipitates appear at the early stages of aging, while the precipitates of γ₂ phase are observed for a longer aging time. When the aging temperature increases, the bainite gradually evolves into γ₂ phase and equilibrium α phase (bcc) precipitates from the remaining parent phase. Thus, the bainite, γ₂, and α phases appear, while the martensite phase disappears progressively in the alloy. The bainitic precipitates decrease the reverse transformation temperature while the γ₂ phase precipitates increase these temperatures with a decrease of solute content in the retained parent phase. On the other hand, these precipitations cause an increasing in hardness of the alloy.

Fatigue characteristics and microcosmic mechanism of Al-Si-Mg alloys under multiaxial proportional loadings

Xiao-song Jiang, Guo-qiu He, Bing Liu, Zheng-yu Zhu, Wei-hua Zhang

2011, 18(4): 437-443. doi: 10.1007/s12613-011-0459-0

中文摘要(274) PDF(8) SpringerLink

摘要:
With the increasing use of Al-Si-Mg alloys in the automotive industry, the fatigue performance of Al-Si-Mg alloy has become a major concern with regard to their reliability. The fatigue characteristics and microcosmic mechanism of an Al-Si-Mg alloy under multiaxial proportional loadings were investigated in this research. As low cycle fatigue life and material strengthening behavior are closely related, the effect of equivalent strain amplitude on the multiaxial fatigue properties was analyzed. Fatigue tests were conducted to determine the influence of equivalent strain amplitude on the multiaxial proportional fatigue properties. The fatigue life exhibits a stable behavior under multiaxial proportional loadings. The dislocation structures of the Al-Si-Mg alloy were observed by transmission electron microscopy (TEM). The dislocation structure evolution of the Al-Si-Mg alloy under multiaxial proportional loadings during low cycle fatigue develops step by step by increasing fatigue cycles. Simultaneously, the dislocation structure changes with the change in equivalent strain amplitude under multiaxial proportional loadings. The experimental evidence indicates that the multiaxial fatigue behavior and life are strongly dependent on the microstructure of the material, which is caused by multiaxial proportional loadings.

Development of a database system for operational use in the selection of titanium alloys

Yuan-fei Han, Wei-dong Zeng, Yu Sun, Yong-qing Zhao

2011, 18(4): 444-449. doi: 10.1007/s12613-011-0460-7

中文摘要(250) PDF(9) SpringerLink

摘要:
The selection of titanium alloys has become a complex decision-making task due to the growing number of creation and utilization for titanium alloys, with each having its own characteristics, advantages, and limitations. In choosing the most appropriate titanium alloys, it is very essential to offer a reasonable and intelligent service for technical engineers. One possible solution of this problem is to develop a database system (DS) to help retrieve rational proposals from different databases and information sources and analyze them to provide useful and explicit information. For this purpose, a design strategy of the fuzzy set theory is proposed, and a distributed database system is developed. Through ranking of the candidate titanium alloys, the most suitable material is determined. It is found that the selection results are in good agreement with the practical situation.

Preparation and characterization of porous ceramics prepared by kaolinite gangue and Al(OH)₃ with double addition of MgCO₃ and CaCO₃

Wen Yan, Nan Li, Bing-qiang Han

2011, 18(4): 450-454. doi: 10.1007/s12613-011-0461-6

中文摘要(191) PDF(9) SpringerLink

摘要:
Porous ceramics were prepared from kaolinite gangue and Al(OH)₃ with double addition of MgCO₃ and CaCO₃ by the pore-forming in-situ technique. The characterizations of porous ceramics were investigated by X-ray diffractometry, scanning electron microscopy, and mercury porosimetry measurements, etc. It is found that although the decomposition of MgCO₃ and CaCO₃ has little contribution to the porosity, the double addition of MgCO₃ and CaCO₃ strongly affects the formation of liquid phase, and then changes the phase compositions, pore characterization, and strength. The appropriate mode is the sample containing 1.17wt% MgCO₃ and 1.17wt% CaCO₃, which has high apparent porosity (41.0%), high crushing strength (53.5 MPa), high mullite content (76wt%), and small average pore size (3.24 μm).

Crystallization characteristics of iron-rich glass ceramics prepared from nickel slag and blast furnace slag

Zhong-jie Wang, Wen Ni, Ke-qing Li, Xiao-yan Huang, Li-ping Zhu

2011, 18(4): 455-459. doi: 10.1007/s12613-011-0462-5

中文摘要(352) PDF(11) SpringerLink

摘要:
The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag (NS) and blast furnace slag (BFS) with a small amount of quartz sand was investigated. A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process. The results show that the iron-rich system has much lower melting temperature, glass transition temperature (T_g), and glass crystallization temperature (T_c), which can result in a further energy-saving process. The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918℃. The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample. The crystallization process can be completed in a few minutes. A distinct boundary between the crystallized part and the non-crystallized part exists during the process. In the non-crystallized part showing a black colour, some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to T_c. In the crystallized part showing a khaki colour, a compact structure is formed by augite crystals.

Effect of moisture on the aging behavior of asphalt binder

Tao Ma, Xiao-ming Huang, Enad Mahmoud, Emil Garibaldy

2011, 18(4): 460-466. doi: 10.1007/s12613-011-0463-4

中文摘要(294) PDF(9) SpringerLink

摘要:
The moisture aging effect and mechanism of asphalt binder during the in-service life of pavement were investigated by laboratory simulating tests. Pressure aging vessel (PAV) test simulating the long-term aging of binder during the in-service life of pavement was modified to capture the long-term moisture aging effect of binder. Penetration grade tests including penetration test, soften point test, and ductility test as well as Superpave^TM performance grade tests including viscosity test, dynamic shear rheometer test, and bending beam rheometer test were conducted to fully evaluate the moisture aging effect of binder. Fourier transform infrared spectroscopy test and Gel-permeation chromatography test were applied to provide a fundamental understanding of the moisture aging mechanism of binder. The results indicate that moisture condition can accelerate the aging of asphalt binder and shorten the service life of asphalt binder. The modified PAV test with moisture condition can well characterize the moisture aging properties of asphalt binder.

High heat loading performance of actively cooled W/Cu FGM-based components

Zhang-jian Zhou, Jun Tan, Dan-dan Qu, Hua Li, Young-jin Yum, Hyun-woo Lim

2011, 18(4): 467-471. doi: 10.1007/s12613-011-0464-3

中文摘要(230) PDF(7) SpringerLink

摘要:
A functionally graded material-based actively water-cooled tungsten-copper mockup with a dimension of 30 mm×30 mm×25 mm was designed and fabricated by infiltration-brazing method. The thicknesses of the pure W layer and W/Cu graded layer were 2 and 3 mm, respectively. High heat flux tests were performed on the mockup using an e-beam device. There is no damage occurring on the joint after heat loading at 5 MW/m². The temperature on the pure W surface is less than 500℃ after irradiation for 100 s at 5 MW/m², while the temperature on the brazing seam/copper surface is around 200℃.

Effects of boron on the microstructure and thermal properties of Cu/diamond composites prepared by pressure infiltration

Ye-ming Fan, Hong Guo, Jun Xu, Ke Chu, Xue-xin Zhu, Cheng-chang Jia

2011, 18(4): 472-478. doi: 10.1007/s12613-011-0465-2

中文摘要(314) PDF(12) SpringerLink

摘要:
Diamond reinforced copper (Cu/diamond) composites were prepared by pressure infiltration for their application in thermal management where both high thermal conductivity and low coefficient of thermal expansion (CTE) are important. They were characterized by the microstructure and thermal properties as a function of boron content, which is used for matrix-alloying to increase the interfacial bonding between the diamond and copper. The obtained composites show high thermal conductivity (>660 W/(m·K)) and low CET (<7.4×10^-6 K^-1) due to the formation of the B₁₃C₂ layer at the diamond-copper interface, which greatly strengthens the interfacial bonding. Thermal property measurements indicate that in the Cu-B/diamond composites, the thermal conductivity and the CTE show a different variation trend as a function of boron content, which is attributed to the thickness and distribution of the interfacial carbide layer. The CTE behavior of the present composites can be well described by Kerner’s model, especially for the composites with 0.5wt% B.

Fabrication and thermal stability of Ni-P coated diamond powder using electroless plating

Ying-hu Dong, Xin-bo He, Rafi Ud-din, Cai-yu Guo, Liang Xu, Yu-ting Huang, Xuan-hui Qu

2011, 18(4): 479-486. doi: 10.1007/s12613-011-0466-1

中文摘要(280) PDF(9) SpringerLink

摘要:
Ni-P coated diamond powder was fabricated successfully by using electroless plating. Effects of active solutions, plating time, reaction temperature, and the components of the plating bath on the Ni-P coating were investigated systematically. Moreover, a study on the thermal stability of Ni-P coated diamond under various atmospheres was performed. The results indicate that Pd atoms absorbed on the diamond surface as active sites can consequently enhance the deposition rate of Ni effectively. The optimized plating bath and reaction conditions improve both the plating speed and the coverage rate of Ni-P electroless plating on the diamond surface. Compared to the diamond substrate, the diamond coated with Ni-P films exhibits very high thermal stability and can be processed up to 900℃ in air and 1300℃ in protective atmosphere such as H₂.

Coating mechanism of nano-TiO₂ films on the surface of ultra-fine calcined coal kaolin particles

Hai Lin, Ying-bo Dong

2011, 18(4): 487-493. doi: 10.1007/s12613-011-0467-0

中文摘要(280) PDF(10) SpringerLink

摘要:
A new type of mineral composite was made by calcined coal kaolin. The interaction mechanism of an inorganic modification reagent TiOSO₄ with the surface of ultra-fine calcined coal kaolin particles (substrate) was studied by X-ray photoelectron spectroscopy. The results show that chemisorption exists in the phase boundary between the modification agent and the substrate surface, while physical adsorption occurs on the modification layers of hydrate titanium dioxide. The interaction force was calculated and analyzed according to DLVO theory between ultra-fine calcined coal kaolin particles and hydrate titanium dioxide nano-particles in the modification system. It is shown that the both electrostatic force and van der Waals force are attractive, and the coacervation between ultra-fine calcined coal kaolin particles and hydrate titanium dioxide nano-particles leads to the coating of hydrate titanium dioxide on the surface of ultra-fine calcined coal kaolin particles.

Existence of multiple solutions for the laminar flow in a porous channel with suction at both slowly expanding and contracting walls

Xin-hui Si, Lian-cun Zheng, Xin-xin Zhang, Ying Chao

2011, 18(4): 494-501. doi: 10.1007/s12613-011-0468-z

中文摘要(255) PDF(8) SpringerLink

摘要:
The asymptotic behavior of solutions of a similarity equation for the laminar flow in a porous channel with suction at both expanding and contracting walls has been obtained by using a singular perturbation method. However, in the matching process, this solution neglects exponentially small terms. To take into account these exponentially small terms, a method involving the inclusion of exponentially small terms in a perturbation series was used to find two of the solutions analytically. The series involving the exponentially small terms and expansion ratio predicts dual solutions. Furthermore, the result indicates that the expansion ratio has much important influence on the solutions.

Boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretching vertical surface with prescribed skin friction

Kartini Ahmad, Roslinda Nazar, Ioan Pop

2011, 18(4): 502-507. doi: 10.1007/s12613-011-0469-y

中文摘要(246) PDF(7) SpringerLink

摘要:
The steady laminar mixed convection boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretched vertical surface with prescribed skin friction were considered. The governing partial differential equations were transformed into a system of ordinary differential equations, which were then solved numerically using the shooting method. Results for the stretching velocity, the local Nusselt number, the temperature, and the velocity profiles are presented for various values of the mixed convection parameter λ and material parameter K when the Prandtl number is equal to 1. Both assisting (heated plate) and opposing (cooled plate) flow regions are considered. It is found that dual solutions exist for both assisting and opposing flows.

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2011年第18卷第4期