International Journal of Minerals, Metallurgy and Materials

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Instrumented borehole drilling for interface identification in intricate weathered granite ground engineering

Zhuoying Tan, Meifeng Cai, Z. Q. Yue, L. G. Tham, C. F. Lee

2007, 14(3): 195-199. doi: 10.1016/S1005-8850(07)60038-3

中文摘要(225) PDF(11) SpringerLink

摘要:
The successful application in drilling for HK simple weathered granite foundation has revealed its further use in instrumented drilling system as a ground investigation tool in the detection of other lithology formations, geohazards, underground water, and boundary of orebody. To expand the further use and test the accuracy in identification of formation, an R-20 rotary-hydraulic drill rig was instrumented with a digital drilling process monitoring system (DPM) for drilling in an intricate decomposed granite site. In this test ground, the boreholes revealed that the weathered granite alternately changes between moderate and strong. The qualitative and quantitative analysis of the penetrating parameters, indicates the effective thrust force, rotary speed, flushing pressure, penetrating rate, and displacement of the bit fluctuate at ground interfaces. It shows that the parameters get a good response with the change of rock strength at the interfaces, which can reveal the change of the intricate granite formation. Besides, a variable-slope method has been established, for identification of dominative and subsidiary interfaces in the granite site. The result from a t-test shows that the confidence of the instrumented drilling system in identification of the geotechnical interfaces is up to 99%.

Mineral

Depressing effect of sodium hexametaphosphate on apatite in flotation of rutile

Hao Ding, Hai Lin, Yanxi Deng

2007, 14(3): 200-203. doi: 10.1016/S1005-8850(07)60039-5

中文摘要(271) PDF(10) SpringerLink

摘要:
The separation of rutile from apatite by flotation and the mechanism of depressing the apatite of sodium hexametaphosphate were studied. The results showed that rutile and apatite could be separated by using alkyl-imino-bismethylene phosphoric acid and sodium hexametaphosphate as a collector and a regulator, respectively. Sodium hexametaphosphate could selectively dissolve calcium ions on the apatite surface, and make calcium ions break away from lattice binding through combining.

Metallurgy

Calculating models of mass action concentrations for NaBr(aq), LiNO₃(aq), HNO₃(aq), and KF(aq) binary solutions

Hanjie Guo, Weijie Zhao, Xuemin Yang

2007, 14(3): 204-211. doi: 10.1016/S1005-8850(07)60040-1

中文摘要(235) PDF(9) SpringerLink

摘要:
The calculating models of mass action concentrations for electrolyte aqueous solutions NaBr-H₂O, LiNO₃-H₂O, HNO₃-H₂O, and KF-H₂O have been developed at 298.15 K and their molalities ranging from 0.1 mol/kg to saturation according to the ion and molecule coexistence theory as well as mass action law. The calculated mass action concentration is based on pure species as the standard state and the mole fraction as the concentration unit, and the reported activities are usually based on infinite dilution as the standard state and molality as the concentration unit. Hence, the calculated mass action concentration must be transformed to the same standard state and concentration unit. The transformation coefficients between calculated mass action concentrations and reported activities of the same component fluctuate in a very narrow range. Thus, the transformed mass action concentrations not only agree well with reported activities, but also strictly obey mass action law. The calculated results show that the new developed models can embody the intrinsic structure of investigated four electrolyte aqueous solutions. The results also indicate that mass action law has its widespread applicability to electrolyte binary aqueous solutions.

Metallurgy

Distribution and segregation of dissolved elements in pipeline slab

Jianhua Liu, Yanping Bao, Xian Dong, Taiquan Li, Yi Ren, Shuai Zhang

2007, 14(3): 212-218. doi: 10.1016/S1005-8850(07)60041-3

中文摘要(272) PDF(9) SpringerLink

摘要:
The chemical composition in a cross section of a high grade pipeline slab was measured point by point (in a scale of 1 μm) using original position statistic distribution analysis (OPA). The result indicated that negative segregation strips of Si, Mn, Mo, Ni, Cr, Nb, Cu, Ti, and V exist in the two sides 24 mm away from the central line, with a width of 8-12 mm, Negative segregation inside the central line is more severe than that outside the central line, and the highest positive segregation of the elements appears closely by the inner sides of the negative segregation strips. No obvious negative segregation strip of S and P is found. Segregation of the elements in the central area is higher than that in the outer and inner arc areas. The segregation of C, Ti, S, and P is high and that of Cr, Cu, Si, and Mn is low in the slab.

Metallurgy

Research on mold flux for hypo-peritectic steel at high casting speed

Heming Zhao, Xinhua Wang, Jiongming Zhang

2007, 14(3): 219-224. doi: 10.1016/S1005-8850(07)60042-5

中文摘要(386) PDF(17) SpringerLink

摘要:
Mold fluxes having adaptable properties were developed in the laboratory to solve quality defects, such as depressions and longitudinal cracks when casting hypo-peritectic steel at high casting speed. Firstly, the effect of components on the high basicity mold flux properties was first studied using the orthogonal method. In the scope of the studied content, Li₂O has the largest effect on the melting temperature, and the least effect on the viscosity; CaF₂ has the largest effect on the viscosity, and the least effect on the melting temperature; Na₂O and CaO/SiO₂ have no obvious influence on the melting temperature and viscosity. Secondly, two powders (Z1 and Z6) have reasonable viscosity-temperature curves, higher solidification temperatures, and porous structure after solidification, but the crystal property of Z6 is worse than that of Z1, and thus Z1 is more suitable for continuous casting hypo-peritectic steel at high casting speed. Thirdly, a higher basicity of powder, a less free enthalpy of crystal compound, and a lower baffle energy are good for a higher tendentiousness of crystal.

Metallurgy

Preparation of special silicon steel grade MgO from hydromagnesite

Xiangyang Zhou, Shanni Li, Jie Li, Hongzhuan Liu, Shangyuan Wu

2007, 14(3): 225-230. doi: 10.1016/S1005-8850(07)60043-7

中文摘要(284) PDF(9) SpringerLink

摘要:
A preparation technology of MgO powder used in special silicon steel from hydromagnesite mineral has been developed. The preparation technology includes the following steps: (1) calcining the hydromagnesite at 700-750℃ for 1.5-2 h; (2) hydrating the calcined hydromagnesite to be slurry containing the solid-liquid ratio of 15-20 g·L^-1; (3) acquiring Mg(HCO₃)₂ solution by carbonating the slurry, the carbonation temperature, CO₂ pressure, and end point PH value of carbonation are less than 40℃, 0.4-0.6 MPa, and 7 respectively during the carbonation process; (4) preparing precipitated basic magnesium carbonate by thermally decomposing the Mg(HCO₃)₂ solution at 90-100℃; (5) obtaining the MgO product by calcining the precipitated basic magnesium carbonate at 850-950℃ for 30-60 min, and adopting flowing nitrogen during the cooling process. By using this technology, more than 80wt% magnesium in hydromagnesite mineral can be extracted, and high-performance MgO products used in special silicon steel can be obtained.

Materials

Influence of secondary carbide precipitation and transformation on abrasion resistance of a 3Cr15Mo1V1.5 white iron

Haohuai Liu, Jun Wang, Baoluo Shen, Hongshan Yang, Shengji Gao, Sijiu Huang

2007, 14(3): 231-235. doi: 10.1016/S1005-8850(07)60044-9

中文摘要(235) PDF(8) SpringerLink

摘要:
The relationship between the secondary carbide precipitation and transformation of the 3Cr15Mo1V1.5 white iron and abrasion resistance was investigated by using optical microscope (OM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the properties of secondary carbides precipitated at holding stage play an important role in the abrasion resistance. After certain holding time at 833 K subcritical treatment, the grainy (Fe, Cr)₂₃C₆ carbide precipitated and the fresh martensite transformed at the holding stage for 3Cr15Mo1V1.5 white iron improve the bulk hardness and abrasion resistance of the alloy. Prolonging holding time, MoC and (Cr, V)₂C precipitations cause the secondary hardening peak and the corresponding better abrasion resistance. Finally, granular (Fe, Cr)₂₃C₆ carbide in situ transforms into laminar M₃C carbide and the matrix structure transforms into pearlitic matrix. These changes weaken hardness and abrasion resistance of the alloy sharply.

Materials

Effect of electrochemical polishing time on surface topography of mild steel

Baocheng Wang, Jinhua Zhu

2007, 14(3): 236-239. doi: 10.1016/S1005-8850(07)60045-0

中文摘要(178) PDF(15) SpringerLink

摘要:
The variation in altitude density function (ADF) of the surface topography of mild steel during electrochemical polishing (ECP) was investigated, and the mechanism of the variation of surface roughness with polishing time was analyzed. The results show that the variation trend of ADF with polishing time is flat-steep-flat; the variation of surface roughness results in the different distributions of surface current density, and there is a fine surface smoothness in the special period of ECP from 4 to 8 s.

Materials

Comprehensive contour prediction model of work rolls in hot wide strip mill

Xiaodong Wang, Quan Yang, Anrui He, Renzhong Wang

2007, 14(3): 240-245. doi: 10.1016/S1005-8850(07)60046-2

中文摘要(197) PDF(9) SpringerLink

摘要:
The predictive calculation of comprehensive contour of work rolls in the on-line strip shape control model during hot rolling consists of two important parts of wear contour calculation and thermal contour calculation, which have a direct influence on the accuracy of shape control. A statistical wear model and a finite difference thermal contour model of work rolls were described. The comprehensive contour is the equivalence treatment of the sum of grinding, wear, and thermal contours. This comprehensive contour calculation model has been applied successfully in the real on-line strip shape control model. Its high precision has been proved through the large amounts of actual roll profile measurements and theoretical analyses. The hit rates (percent of shape index satisfying requirement) of crown and head flatness of the strips rolled, by using the shape control model, which includes the comprehensive contour calculation model, have about 16% and 10% increase respectively, compared to those of strips rolled by using manual operation.

Materials

Ageing behavior of an Al-Zn-Mg-Cu alloy pre-stretched thick plate

Zhihui Li, Baiqing Xiong, Yongan Zhang, Baohong Zhu, Feng Wang, Hongwei Liu

2007, 14(3): 246-250. doi: 10.1016/S1005-8850(07)60047-4

中文摘要(232) PDF(14) SpringerLink

摘要:
The ageing behavior of a pre-stretched thick plate of Al-Zn-Mg-Cu alloy was systemically studied including one-step ageing, two-step ageing, and retrogression and reageing treatment (RRA). One-step ageing of the alloy resulted in peak ultimate tensile strengths of 595 and 575 MPa after 22 and 6 h at 120 and 135℃, respectively. The strengthening phase in peak aged (T6 temper) alloy contained GP zones and the η' phase predominantly. After two-step ageing, the electrical conductivity was increased markedly, but the pre-stretched thick plate sacrificed a great loss of strength. RRA treatment provided a method for maintaining the strength close to that obtained by T6 temper and for obtaining the high electrical conductivity close to that obtained by T7 temper; the ultimate tensile strength and electrical conductivity were 583 MPa and 21.0 MS/m, respectively. TEM analysis of T7 and RRA specimens revealed two types of precipitates that contributed to age strengthening i.e. the η' and η phases.

Materials

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing

Yanhang Wang, Junpin Lin, Yuehui He, Yanli Wang, Guoliang Chen

2007, 14(3): 251-255. doi: 10.1016/S1005-8850(07)60048-6

中文摘要(270) PDF(14) SpringerLink

摘要:
Densification behavior of high Nb containing TiAl alloys through reactive hot pressing was investigated. The results showed that the density of the sample hot pressed at 1400℃ could reach a near full density of 98.37%. However, the densification abnormality was observed at 1500℃. The diffusion of elemental Nb during microstructural evolution is an important aspect affecting densification, which will form pore nests. With the increase of hot pressing temperature, the diffusion of Nb becomes more adequate. HIP (Hot isostatic pressing) treatment can only decrease porosity to some extent, but cannot eliminate it completely.

Materials

Phase transformation behaviors and shape memory effects of TiNiFeAl shape memory alloys

Li Xiao, Fushun Liu, Huibin Xu

2007, 14(3): 256-260. doi: 10.1016/S1005-8850(07)60049-8

中文摘要(202) PDF(7) SpringerLink

摘要:
Measurements of electrical resistivity, X-ray diffraction, and tensile test at room temperature and -196℃ were performed to investigate the effects of Al addition substituting Ni on the phase transformation behaviors, the mechanical properties, and the shape memory effects of Ti₅₀Ni₄₇Fe₂Al₁ and Ti₅₀Ni_46.5Fe_2.5Al₁ alloys. It is found that 1at% Al addition dramatically decreases the martensitic start transformation temperature and expands the transformation temperature range of R-phase for TiNiFeAl alloys. The results of tensile test indicate that 1at% Al improves the yield strength of Ti₅₀Ni₄₇Fe₂Al₁ and Ti₅₀Ni_46.5Fe_2.5Al₁ alloys by 40% and 64%, but decreases the plasticity to 11% and 12% from 26% and 27% respectively. Moreover, excellent shape memory effect of 6.6% and 7.5% were found in Ti₅₀Ni₄₇Fe₂Al₁ and Ti₅₀Ni_46.5Fe_2.5Al₁ alloys, which results from the stress-induced martensite transformation from the R-phase.

Materials

Reaction dynamics in the combustion synthesis system of Al-CrO₃-Al₂O₃-NaF-N₂-O₂

Dazheng Yang, Yue Zhang, Degang Li, Dianwei Qi, Wei Deng, Dayong Xun

2007, 14(3): 261-265. doi: 10.1016/S1005-8850(07)60050-4

中文摘要(297) PDF(7) SpringerLink

摘要:
A new material with heat-resistant and adiabatic characteristics and high strength was prepared using the combustion synthesis method by mixed powders of CrO₃, Al, Al₂O₃, and NaF in atmospheric gas. The reaction dynamic process of the Al-CrO₃-NaF-Al₂O₃-N₂-O₂ new material system by the combustion synthesis method was discussed based on the observation results by SEM, EDS, and XRD in combination with the combustion front quenching method (CFQM) and the relation curves between reaction free enthalpies and the corresponding temperatures. The combustion synthesis mechanism and the formation reasons of the phase in the combustion product were analyzed.

Materials

Microstructure and electrical properties of Y₂O₃-doped ZnO-based varistor ceramics prepared by high-energy ball milling

Hongyu Liu, Xueming Ma, Dongmei Jiang, Wangzhou Shi

2007, 14(3): 266-270. doi: 10.1016/S1005-8850(07)60051-6

中文摘要(293) PDF(15) SpringerLink

摘要:
Y₂O₃-doped ZnO-based varistor ceramics were prepared using high-energy ball milling (HEBM) and low-temperature sintering technique, with voltage-gradient of 1934-2197 V/mm, non-linear coefficients of 20.8-21.8, leakage currents of 0.59-1.04 μA, and densities of 5.46-5.57 g/cm³. With increasing Y₂O₃ content, the voltage-gradient increases because of the decrease of ZnO grain size; the non-linear coefficient and the leakage current improve but the density decreases because of more porosity; the donor concentration and density of interface states decrease, whereas the barrier height and width increase because of the acceptor effect of Y₂O₃ in varistor ceramics.

Materials

Comparative study of β-Si₃N₄ powders prepared by SHS sintered by spark plasma sintering and hot pressing

Ling Bai, Xiaodong Mao, Weiping Shen, Changchun Ge

2007, 14(3): 271-275. doi: 10.1016/S1005-8850(07)60052-8

中文摘要(218) PDF(13) SpringerLink

摘要:
β-Si₃N₄ powders prepared by self-propagating high-temperature synthesis (SHS) with additions of Y₂O₃ and Al₂O₃ were sintered by spark plasma sintering (SPS). The densification, microstructure, and mechanical properties of Si₃N₄ ceramics prepared using this method were compared with those obtained by hot pressing process. Well densified Si₃N₄ ceramics with finer and homogeneous microstructure and better mechanical properties were obtained in the case of the SPS technique at 200℃ lower than that of hot pressing. The microhardness is 15.72 GPa, the bending strength is 716.46 MPa, and the fracture toughness is 7.03 MPa·m^1/2.

Materials

In situ prepared Al-Si alloy matrix composites reinforced by γ-Al₂O₃p

Lan Jiang, Bo Jiang, Zhaofei Wang, Yue Wang, Ji Liu

2007, 14(3): 276-279. doi: 10.1016/S1005-8850(07)60053-X

中文摘要(271) PDF(8) SpringerLink

摘要:
A γ-Al₂O₃ particles reinforced Al-Si alloy matrix composite was fabricated by adding NH₄Al(SO₄)₂ to molten aluminum alloy. TEM observation shows that in-situ γ-Al₂O₃ particles are generally spherical and uniformly distributed in the matrix. The results of dry sliding wear tests show that the wear resistance of the composites increases with increasing mass fraction, and the volume loss is considerably lesser than that of the matrix and is lesser than that of the composites by adding γ-Al₂O₃ particles directly.

Materials

Estimation of interfacial damage in composites with reinforced particles based on ultrasonic data

Xiqiang Liu, Peijun Wei, Li Zhang, Hang Wang

2007, 14(3): 280-285. doi: 10.1016/S1005-8850(07)60054-1

中文摘要(230) PDF(7) SpringerLink

摘要:
The scattering of elastic waves by a spherical particle with imperfect interface and the nondestructive detection of interfacial damage were studied. First, the scattering of elastic waves by a spherical particle with imperfect interface, i.e. spring interface model, was studied. Then, multiple scattering by random distributed particles was investigated and the equations to evaluate the velocity and attenuation of effective waves defined by statistic averaging were given. Furthermore, on the basis of the established relation between the velocity and interfacial constants, a method to evaluate the interfacial damage nondestructively from the ultrasonic data was proposed. Numerical simulation was performed for the SiC-Al composites. The velocities of the effective waves were computed to show the influence of the interface constants. Using the genetic algorithm, the interfacial damage was evaluated from the synthetic experimental data with various noise levels. The numerical results showed the feasibility of the method proposed.

Materials

Effect of Pd ions in the chemical etching solution

Guixiang Wang, Ning Li, Deyu Li

2007, 14(3): 286-289. doi: 10.1016/S1005-8850(07)60055-3

中文摘要(277) PDF(11) SpringerLink

摘要:
The acrylonitrile-butadiene-styrene (ABS) surface was etched by dipping it into chromic acid-sulfuric acid containing a trace amount of palladium. The surface roughness, activity, and valence bond were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results showed that with the increase of Pd concentration in the etching solution the ABS surface roughness reduced. The ratio of O to C increases and forms a large amount of O=C-O functional groups by dipping into Pd contained etching solution, thus the amount of colloids palladium adsorption increases. The carboxyl group acts as the adsorption site for the Pd/Sn catalyst.

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2007年第14卷第3期