In this study, 7075 Al/AZ31B Mg/7075 Al laminated composites were prepared by hot roll bonding method. microstructure and bonding strength of the experimental laminated composites, and thickness ratio of the constitue...
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In this study, 7075 Al/AZ31B Mg/7075 Al laminated composites were prepared by hot roll bonding method. microstructure and bonding strength of the experimental laminated composites, and thickness ratio of the constituent layers after hot rolling were evaluated. Effects of reduction ratio and rolling temperature on the microstructure, bonding strength and thickness ratio were also studied. Dynamic recrystallization microstructures were observed in the composite. The bonding strength decreased with reduction ratio and rolling temperature due to the increase in the grain size and diffusion layer width with the reduction ratio and rolling temperature. The maximal bonding strength of the experimental laminated composite was 66 MPa. The thickness fraction of the Mg alloy plate after hot rolling decreased with the reduction ratio and rolling temperature. (C) 2010 Elsevier B.V. All rights reserved.
Three types of activators such as sodium hydroxide,calcium oxide and triethanolamine(TEA)are used to establish different activation environments to address the problems associated with the process of activating fly as...
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Three types of activators such as sodium hydroxide,calcium oxide and triethanolamine(TEA)are used to establish different activation environments to address the problems associated with the process of activating fly ash *** conducted mechanical tests and numerical simulations to understand the evolution of microstructure,and used environmental scanning electron microscopy(ESEM)and energy dispersive spectroscopy(EDS)techniques to analyze the microenvironments of the *** mechanical properties of fly ash paste under different activation conditions and the changes in the microstructure and composition were *** results revealed that under conditions of low NaOH content(1%-3%),the strength of the sample increased *** the content exceeded 4%,the rate of increase in strength *** on the results,the optimal NaOH content was identified,which was about 4%.A good activation effect,especially for short-term activation(3-7 d),was achieved using TEA under high doping *** activation effect was poor for long-term strength after 28 *** CaO content did not significantly affect the degree of activation *** maximum effect was exerted when the content of CaO was 2%.The virtual cement and concrete testing laboratory(VCCTL)was used to simulate the hydration process,and the results revealed that the use of the three types of activators accelerated the formation of Ca(OH)_(2) in the *** activators also corroded the surface of the fly ash particles,resulting in a pozzolanic *** active substances in fly ash were released efficiently,and hydration was *** pores were filled with hydration products,and the microstructure changed to form a new frame of paste filling that helped improve the strength of fly ash paste.
Boron suboxide(B6O)is recognized as a superhard material with a low mass density,high resistance to chemical wear,and excellent wear *** its desirable properties,the limited fracture tough-ness of B6O restricts its ap...
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Boron suboxide(B6O)is recognized as a superhard material with a low mass density,high resistance to chemical wear,and excellent wear *** its desirable properties,the limited fracture tough-ness of B6O restricts its application in industrial *** study presents the structural and me-chanical characterization of B6O-SiC nanocomposites,which were synthesized via a high-pressure high-temperature sintering process of B6O powders and SiC *** sintering process induced fragmen-tation of SiC whiskers,resulting in the homogenous distribution of SiC fragments within the B6O *** increase in SiC content was observed to decrease the composite's hardness,while initially reducing then enhancing its *** nanocomposites containing 20 wt％and 30 wt％SiC whiskers exhibited significant improvements in fracture toughness,averaging 6.5 MPa m1/2 and 7.0 MPa m1/2,respectively-approximately threefold the toughness of polycrystalline B6O-while sustaining high hardness values of 36.3 GPa and 35.6 GPa on *** analyses revealed that the composites'superior me-chanical performance is due to the presence of strong grain boundaries,as well as a high density of nan-otwins and stacking *** findings demonstrate a viable method for producing B6O-based nanocom-posites with enhanced hardness and toughness,potentially expanding their industrial applicability.
This work aimed to(i)understand conventional and pulse gas tungsten arc welding(GTAW)of AZ31B,and(ii)explore high frequency welding(100 Hz-1500 Hz).GTA welding with alternating current(AC)and direct current electrode ...
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This work aimed to(i)understand conventional and pulse gas tungsten arc welding(GTAW)of AZ31B,and(ii)explore high frequency welding(100 Hz-1500 Hz).GTA welding with alternating current(AC)and direct current electrode positive(DCEP)polarities yielded crack-free partial penetration welds for6 mm thick AZ31B alloy *** under direct current electrode negative(DCEN)polarity with identical parameters as that for AC and DCEP resulted in full penetration welds that had ***-free full-penetration welds could be accomplished with pulse GTA welding using DCEN polarity at a pulse frequency of 1 Hz with a pulse duration ratio of 1:*** resultant DCEN P 1:1 weld metal had a microstructure finer than the conventional DCEN *** produced with pulse duration ratios of 1:2and 1:4 lacked penetration but had a much finer microstructures because of the lower heat *** arc constriction by the high frequency pulsing in the Activ Arc■-High frequency(AA-HF)mode welding was responsible for deeper *** produced under DCEN pulsing and AA-HF conditions had hardness higher than conventional DCEN,DCEP and AC GTA welds,attributed to the finer ***-HF GTA welding produced defect free deeper penetration welds with good microstructural features/mechanical properties and also gave an advantage of 50%enhanced productivity when welded at1500 Hz.
The microstructure and magnetic properties of Fe_(40)Co_(40)Zr_(9)B_(10)Ge_(1)(Mo-free)and Fe_(40)Co_(40)Zr_(5)Mo_(4)B_(10)Ge_(1)(Mocontaining)nanocrystalline alloys,prepared using an amorphous crystallization method,...
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The microstructure and magnetic properties of Fe_(40)Co_(40)Zr_(9)B_(10)Ge_(1)(Mo-free)and Fe_(40)Co_(40)Zr_(5)Mo_(4)B_(10)Ge_(1)(Mocontaining)nanocrystalline alloys,prepared using an amorphous crystallization method,were *** addition affects the crystallization of the Fe_(40)Co_(40)Zr_(9)B_(10)Ge_(1) amorphous alloy and decreases the grain size of theα-Fe(Co)phase below 650℃.For the Mo-free alloy annealed at 600℃ and the Mo-containing alloy annealed at 575℃,with a singleα-Fe(Co)crystallization phase and approximately similar crystallization volume fractions,the Mo-containing alloy showed smaller,more regularly shaped grains and a significantly narrower grain-size distribution than the Mo-free *** Fe and Co contents in the nanograins of the two alloys also *** the Mo-free alloy,a higher concentration of Co distributed in the residual amorphous *** the Mo-containing alloy,a higher concentration Co dissolved in the *** specific saturation magnetization and coercivity of the Mo-free alloy were 1.05-and 1.59-times higher than those of the Mo-containing alloy,respectively.
YBa_(2)Cu_(3)O_(7-x)(YBCO)films with low microwave surface resistance(RS)are essential for high temperature superconducting microwave *** oxygen pressure during deposition has been found to influence RS *** this work,...
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YBa_(2)Cu_(3)O_(7-x)(YBCO)films with low microwave surface resistance(RS)are essential for high temperature superconducting microwave *** oxygen pressure during deposition has been found to influence RS *** this work,we deposited highly c-axis aligned YBCO films on single crystal MgO(001)substrates under different oxygen pressures via pulsed laser *** detailed microstructure was characterized with three-dimensional reciprocal space mapping(3D-RSM)method and their microwave surface resistance was also measured with resonant cavity perturbation *** found that the variation of oxygen pressure can affect film microstructure,including grain orientation distribution and the concentration of crystal *** microstructure modulation can explain RS dependence on the oxygen pressure.
In-situ formed high Mn steel coating reinforced by carbides was formed by laser surface alloying(LSA).Laser alloyed layers on 1Cr18Ni9Ti steel with Mn+W_(2)C(specimen A),Mn+NiWC(specimen B)and Mn+SiC(specimen C)powder...
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In-situ formed high Mn steel coating reinforced by carbides was formed by laser surface alloying(LSA).Laser alloyed layers on 1Cr18Ni9Ti steel with Mn+W_(2)C(specimen A),Mn+NiWC(specimen B)and Mn+SiC(specimen C)powders were fabricated to improve the wear and corrosion behavior of 1Cr18Ni9Ti steel blades in high speed *** evolution,phases,element distribution,microhardness,wear and corrosion behavior of the laser alloyed layers were *** indicated that high Mn steel matrix composites with undissolved W_(2)C,WC and other in-situ formed carbides were formed by LSA with Mn+W_(2)C and Mn+NiWC while SiC totally dissolved into the high Mn matrix when adding Mn+*** as the binding phase in Ni-WC powder decreased the crack sensitivity of the alloyed layer as compared with the addition of W_(2)C *** improvement in average microhardness was achieved in the matrix in specimen A,B and C,with the value of 615,602 and 277 HV_(0.5),while that of the substrate was 212 HV_(0.5).The increase of microhardness,wear and corrosion resistance is highly corelated to microstructure,formed phases,type and content of carbides,micro-hardness and toughness of the alloyed layers.
This study systematically investigated the microstructure, mechanical properties, and corrosion behavior of an extruded Zn-0.2Mg alloy processed by multi-directional forging (MDF) at 100 °C. The mean gra...
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This study systematically investigated the microstructure, mechanical properties, and corrosion behavior of an extruded Zn-0.2Mg alloy processed by multi-directional forging (MDF) at 100 °C. The mean grain size was remarkably decreased from 17.2 ± 0.5 µm to 1.9 ± 0.3 µm, and 84.4% of the microstructure was occupied by grains of below 1 µm in size after applying three MDF passes. Electron backscattered diffraction examinations revealed that continuous dynamic recrystallization, progressive lattice rotation, and particle-stimulated nucleation mechanisms were recognized as contributing to microstructural evolution. Furthermore, transmission electron microscopy results showed that nanoparticles of Mg/Zn dynamically formed under high strain MDF, while the initial extrusion fiber texture was altered to be < 0001 > parallel to the final forging axis. A synergistic effect of grain refinement, texture evolution, second-phase precipitates, and dislocation strengthening resulted in an increased ultimate tensile strength of 232 ± 5 MPa after three MDF passes. However, this was accompanied by a reduction in the elongation (8 ± 2.1%). Additionally, a high corrosion rate of 0.59 mm/year was measured for the experimental alloy fabricated by 3 MDF passes. In agreement with the latter, electrochemical impedance spectroscopy results indicated that the grain refinement improved the passivation kinetics of the oxide layer.
Using lightweight materials is essential for addressing the energy crisis and mitigating environmental pollution. This study investigates the fabrication of 2017 aluminum alloy wire rod coils using continuously cast a...
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Using lightweight materials is essential for addressing the energy crisis and mitigating environmental pollution. This study investigates the fabrication of 2017 aluminum alloy wire rod coils using continuously cast and directly rolled (CCDR) technology. CCDR is an efficient process that streamlines production, shortens cycle times, reduces costs, and minimizes energy consumption. This research aimed to improve the mechanical properties of CCDR-manufactured 2017 aluminum alloy under elevated temperatures and repetitive heating-cooling cycles. Experiments were conducted to evaluate the effects of various heat treatment parameters on the alloy's microstructure, mechanical strength, and crack growth, both in its raw state and after cold rolling. The findings revealed that a solution treatment at 570 degrees C followed by aging enhanced the alloy's strength and induced dynamic strain aging (DSA). However, high-temperature solution treatment also resulted in grain coarsening and precipitation, negatively impacting the alloy's fatigue life. High-temperature tensile tests showed that the alloy retained its strength as the temperature increased, with tensile strength exceeding 200 MPa at 200 degrees C. During thermal fatigue testing, ductility gradually decreased after 500 heating-cooling cycles. The Al2Cu precipitates and the texture produced by the CCDR process contributed to the 2017 aluminum alloy's excellent mechanical properties at elevated temperatures and under repeated thermal cycling. This research is significant as it offers new insights into the microstructural evolution and fracture mechanisms of CCDR-manufactured 2017 aluminum alloy, thereby providing valuable knowledge for producing aerospace-grade aluminum alloys through innovative processing techniques.
This study investigated the microstructure and texture evolution of HX (Hastelloy X), HX-C (CeO2 doped), and HX-W (wrought) alloys fabricated using selective laser melting (SLM). HX and HX-C samples exhibited a finer ...
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This study investigated the microstructure and texture evolution of HX (Hastelloy X), HX-C (CeO2 doped), and HX-W (wrought) alloys fabricated using selective laser melting (SLM). HX and HX-C samples exhibited a finer grain structure (10-25 mu m and 5-15 mu m, respectively) compared to HX-W (20-50 mu m) in the XY plane (normal to the building direction) with dominant (100) grain orientation and significant elongation in the XZ plane (parallel to the building direction). The presence of low-angle grain boundaries (LAGBs) was higher in HX (60.7%) and HX-C (64.9%) compared to HX-W (1.4%), indicating higher internal energy and stored energy within the grains. The orientation distribution function (ODF) analysis revealed similar texture patterns in HX and HX-C samples for both XY and XZ planes, suggesting minimal influence of cerium oxide on texture development. Pole figure analysis confirmed a strong <110> fiber texture for HX and HX-C, further suggesting minimal impact on texture from cerium addition. Conversely, HX-W displayed a mixed grain orientation with reduced LAGBs and a distinct texture, indicating a more advanced recrystallization state. These findings suggest that cerium oxide addition refines the grain structure and enhances specific grain orientation while minimally affecting the overall texture development during SLM processing.
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