共查询到17条相似文献，搜索用时 187 毫秒
1.
LI Jun TIAN Rui XIAO Xue-shan School of Materials Science Engineering Shanghai University Shanghai P.R.China 《上海大学学报(英文版)》2007,(5)
The hot hardness behavior of Zr_(52.5)Al_(10)Ni_(10)Cu_(15)Be_(12.5) bulk metallic glass is studied from ambient temperature to the temperature over T_x (the onset crystallization temperature) using a hot macro-hardness tester and scanning electron microscopy (SEM).The results show that the hot hardness behavior of Zr_(52.5)Al_(10)Ni_(10)Cu_(15)Be_(12.5) bulk metallic glass can be classified into 4 zones:the glassy zone in which the hardness almost linearly decreases with the increase of temperature,the viscoelastic zone in which the hardness is nearly unchanged,the viscous flow zone in which the hardness quickly tends towards near zero with temperature,and the crystallization zone in which the hardness sharply increases.The high temperature deformation behavior and the easy processable deformation region for bulk metallic glasses are also discussed on the basis of the hot marco-hardness. 相似文献
2.
Zr65Al10Ni10Cu15, Zr52.5Al10Ni10Cu15Be12.5 and Zr52.5Al10Ni14.6 Cu17.9Ti5bulk amorphous alloys were prepared by copper mould casting. The crystallization kinetics was measured by differential scanning calorimeter(DSC) with different heating rates, and the activation energy was calculated using Kissinger equation. The relationship between thermal stability and rate constant of crystallization reaction is discussed on the view of crystallization kinetics, and the effect of small atom Beryllium on thermal stability of bulk amorphous alloys is also studied. 相似文献
3.
Surface morphologies of Zr52.5 Al10 Ni10 Cu15 Be12.5 bulk metallic glass after being rolled at both a temperature around T9 and near （ Tx - 50） K were investigated with a scanning electron microscopy. Macroscopic and microscopic observation results show that squamae, cracks, steps and wedges exist on the surface when the samples were rolled at temperatures around Ty. However, a smooth and fiat surface appears when the samples were rolled at temperatures near （ Tx - 50） K. These results indicate that the mode of deformation in the supercooled liquid region is a partially homogeneous flow at a temperature around T9, and a fully homogeneous one at temperatures near （ Tx - 50） K. According to the results, it is more feasible to roll the amorphous alloys at temperatures near （ Tx - 50） K to obtain parts with smooth and fiat surface. 相似文献
4.
The deformation behavior of hot isostatic pressing (HIP) FGH96 superalloy was characterized in the temperature range of 1 000-1 100℃and strain rate range of 0.001-0.1s-1 using hot compression testing. The flow curves of HIP FGH96 superalloy during hot deformation was analyzed systematically. The results show that deformation temperature, strain rate and strain are the main influence factors on flow stress of HIP FGH96 superalloy during hot deformation. The flow stress displays a peak at a critical strain and then decreases with further increase in strain. For a given strain, the flow stress decreases with the increase of deformation temperature, and increases with the increase of strain rate. A mathematical model of these flow curves was established through regression analysis and taking the strain as a modification factor. The calculated stress values agree well with the experimental values. 相似文献
5.
Junaidi Syarif Agung Iswadi Mariyam Jameelah Ghazali Zainuddin Sajuri Mohd Zaidi Omar 《浙江大学学报(A卷英文版)》2013,14(12):906-914
The effect of solute Cu and Cu precipitates on the wear behavior of ferritic iron under an unlubricated condition was investigated. The specific wear rate of Cu-containing steel abruptly decreased up to 50 N of load, and then gradually decreased with further increased load. The specific wear rate of the as-quenched specimen, in which Cu was in a solid solution, was the lowest among all the specimens at low loads, and all specimens had almost the same specific wear rate at high loads. Subsurface observation showed that the hardness increments of all specimens decreased with increased depth below the worn surface. The as-quenched specimen had a relatively large depth of deformed region than the other specimens even though the increments in hardness were almost the same for all specimens at low loads. With the same hardness at an unworn state, the as-quenched and over-aged specimens exhibited a substantial increase in hardness and large deformed regions below the worn surfaces. This finding indicated that the enhancement in plastic deformation and work hardening led to the decrease in the specific wear rate of the as-quenched specimen at low loads and the improvement in the wear resistance of all specimens at high loads. 相似文献
6.
The hot compressive deformation of extruded AZ31 magnesium alloy with the mass fractions of Al and Zn equal to 3%and 1% respectively is studied by a Gleeble-1500D thermal mechanical simulator over the temperature range from 200℃to 400℃ and the strain rate from 10^-3 s^-1 to 10^0s^-1.The true stress-strain curves of the strain of 65% are tested.The deformation activation energy is obtained and the flow stress model is established by analyzng the effects of strain rate and temperature on the flow stress.Zener-Hollomon parameter is introduced to describe the softening behaviors of AZ31 magnesium alloy resulted from dynamic recrystallization during the hot compressive deformation,whose natural logarithm is linear with the critical strain of dynamic recrystallization. 相似文献
7.
Aluminum nitride （AlN）/borosilicate glass composites were prepared by the tape casting process and hot-press sintered at 950 ℃ with AIN and SiO2-B203-ZnO-Al2O3-Li2O glass as starting materials. We characterized and analyzed the variation of the microstructure, bulk density, porosity, dielectric constant, thermal conductivity and thermal expansion coefficient （TEC） of the ceramic samples as a function of AIN content. Results show that AIN and SiO2-B2O3-ZnO-Al2O3-Li2O glass can be sintered at 950 ℃, and ZnAI204 and Zn2SiO4 phase precipitated to form glass-ceramic. The performance of the ceramic samples was determined by the composition and bulk density of the composites. Lower AlN content was found redounding to liquid phase sintering, and higher bulk density of composites can be accordingly obtained. With the increase of porosity, corresponding decreases were located in the dielectric constant, thermal conductivity and TEC of the ceramic samples. When the mass fraction of AlN was 40%, the ceramic samples possessed a low dielectric constant （4.5-5.0）, high thermal conductivity （11.6 W/（m.K）） and a proper TEC （3.0× 10^-6 K^-1 which matched that of silicon）. The excellent performance makes this kind of low temperature co-fired ceramic a promising candidate for application in the micro-electronics packaging industry. 相似文献
8.
Studies on the sintering, microstructure, mechanical properties and low temperature degradation behavior of yttria stabilized-tetragonal zirconia polycrystal （3Y-TZP） were carried out. The results show that the addition of Al2O3 and MgO improve the sintering at low temperatures, and cause exaggerated grain growth and the transformation of tetragonaI-ZrO2 to monoclinic-ZrO2 with corresponding changes in the mechanical properties. The addition of the yttria-free monoclinic zirconia particles change the overall yttria distribution and induce an active transformation toughening mechanism. Furthermore, the dispersed yttria-free ZrO2 can inhibit the tetragonal zirconia transformation, which is beneficial to the improvement of the low temperature degradation behavior of 3Y- TZP ceramics. 相似文献
9.
Pd77Cu6Si17 （PCS） tbin film metallic glasses （TFMGs） with high glass forming ability and hardness were selected as a hard coating for improving the surface hardness ofAZ31 magnesium alloy. Both microindentation and nanoindentation tests were conducted on specimens with various PCS film thicknesses from 30 to 2000 nm. The apparent hardness and the relative indenta- tion depth （fl） were integrated using a quantitative model. The interaction parameters involved and relative hardness values were extracted from iterative calculations. According to the results, surface hardness can be enhanced greatly by PCS TFMGs in the shallow region, followed by gradual decrease with increasing fl ratio. In addition, specimens with thinner coatings （e.g., 200 nm） showed greater substrate-film interaction and those with thick coatings （e.g., 2000 nm） became prone to film cracking. The op- timum TFMG coating thickness in this study was estimated to be around 200 nm. 相似文献
10.
《天津大学学报(英文版)》2016,(3)
Self-made enriched 10 B boric acid as raw material was purified by recrystallization. The effects of final crystallization temperature, crystallization time, stirring speed, crystallization frequency and other factors on the purity were investigated. The appropriate operating condition was that the final crystallization temperature and time were 5,℃ and 10 h respectively under a low-speed stirring for crystallizing twice, which would make the purity and yield of boric acid reach 99.94% and 95.36%, respectively. Taking this as foundation, recrystallization process was optimized with acetone as anti-solvent, whose amount was the most important index. The boric acid solution was added into acetone and recrystallized under the same condition, and the purity and yield of boric acid would reach 99.98% and 99.61%, respectively. The product detected by XRD was confirmed as boric acid crystal. Main ion concentration in the product was detected by ICP, which basically met the national standard of high purity. Crystal morphology of boric acid was observed by SEM. 相似文献
11.
Zr65 Al10 Ni10 Cu15, Zr52.5 Al10 Ni10 Cu15 Be12.5 and Zr52.5 Al10 Ni14.6 Cu17.9 Ti5 bulk amorphous alloys were prepared by copper mould casting. The crystallization kinetics was measured by differential scanning calorimeter(DSC) with different heating rates, and the activation energy was calculated using Kissinger equation. The relationship between thermal stability and rate constant of crystallization reaction is discussed on the view of crystallization kinetics, and the effect of small atom Beryllium on thermal stability of bulk amorphous alloys is also studied. 相似文献
12.
1IntroductionSince a non-noble bulk metallic glassy alloy was dis-covered byInoue ,et al.[1]in 1988 , many stable amor-phous alloy systems with higher glass-forming abilityand lower critical cooling rates have been developed .Among them, Zr-based metallic glassy alloys are in-tenselyinvestigated because of their wider supercooledliquid region and other favorable thermodynamic andmechanical properties .In general ,surface morphologyof amorphous alloy parts is veryi mportant forindustri-al and … 相似文献
13.
《天津大学学报(英文版)》2020,(4)
The eff ect of Zn interlayer on the microstructural evolution and mechanical behavior of dissimilar ultrasonic-spot-welded Al/Cu joints was investigated. The tensile lap shear strength in relation to welding energy was analyzed. The experimental results show that two intermetallic compounds, Cu_5Zn_8 and Al_2Cu, were generated at the interface of the ultrasonic-spotwelded Al/Cu joint with a Zn interlayer. The primary joining mechanisms of the joint included the intermetallic compound bonding and metallic bonding caused by solid shear plastic deformation. Meanwhile, with increasing welding energy, the plastic deformation of the material became more substantial. With increasing welding energy, the tensile lap shear strength of the joints fi rst increased and then decreased for the ultrasonic-spot-welded Al/Cu joints with and without Zn interlayers. Under the energy input of 700 J, the bearing load capacity of the ultrasonic-spot-welded Al/Cu joints with a Zn interlayer improved signifi cantly due to the observed intermetallic compound(Cu_5Zn_8). 相似文献
14.
孙龙 《实验室研究与探索》2005,24(8):19-20
介绍了用于压力测量的新型bridgman装置，并结合X射线衍射分析技术（XRD）研究了常压、高压条件下Zr41．2Ti13．8Cu12．5Ni10Be22．5块体非晶合金的晶化。结果表明，在相同的退火条件下（400℃，退火3小时），增大压力有利于Zr41．2Ti13．8Cu12．5Ni10Be22．5块体非晶合金的晶化；压力越大获得晶化相的晶粒尺寸越大。 相似文献
15.
基于DEFORM-3D有限元分析软件,采用刚黏塑性热力耦合有限元模拟技术,对4032铝合金销轴热挤压成形过程进行了模拟与分析,获得了金属流动、挤压载荷、等效应变以及坯料内部温度等相关场量的变化规律。结果表明：4032铝合金销轴热挤压变形时,坯料心部金属的流动速度大于表层金属;内部变形可分为4个区域,即未变形区、变形区、已变形区和死区;坯料在凹模模口附近变形最为剧烈,挤压载荷急剧增加,等效应变梯度最大,局部温升明显。 相似文献
16.
The synthesis of methanol and dimethyl ether (DME) from CO hydrogenation has been investigated on Cu-based catalysts. A series
of Cu/ZnO/Al2O3 catalysts were prepared using a solvent-free routine which involved a direct blend of copper/zinc/aluminum salts and citric
acid, followed by calcination at 450 °C. The calcination processes were monitored using thermogravimetry differential scanning
calorimetry (TG-DSC). Catalysts were further characterized using N2 adsorption, scanning electronic microscopy (SEM), X-ray diffraction (XRD), N2O oxidation followed by H2 titration, and temperature-programmed reduction with H2 (H2-TPR). The reduction processes were also monitored with in-situ XRD. The physicochemical properties of catalysts depended
strongly on the types of precursor salts, and catalysts prepared using Al acetate and Cu nitrate as starting materials had
a larger surface area, larger exposed metallic copper surface area, and lower reduction temperature. The CO hydrogenation
performances of these catalysts were compared and discussed in terms of their structures. Catalysts prepared with copper nitrate,
zinc and aluminum acetates exhibited the highest catalytic activity. 相似文献
17.
利用较低纯度的原材料通过真空铜模吸铸法成功地制备了直径为2mm的（Fe0．5Co0．5）72B19．2Si4．8Nb4块体非晶合金。用X射线衍射（XRD）和示差扫描量热分析仪（DSC）研究了该非晶合金的晶化行为。结果表明,升温速率为10℃／min时,玻璃转变温度Tg为568．3℃,晶化起始温度Tx为598．6℃,晶化峰值温度Tp为608．0℃．随着升温速率的增加,特征温度Tg,Tx,Tp向高温区移动．用Kissinger法得到的玻璃转变激活能E。为272．3KJ／mo｜,晶化激活能E：为386．2KJ／too｜,晶化峰值激活能Ep为401．9KJ／mol,用Ozawa法得到的特征温度激活能与用Kissinger法得出的激活能变化趋势是一致的,都有Ep〉Ex〉Eg 此外,用Ozawa法分析了晶化激活能随晶化体积分数的关系,表明随着晶化体积分数的逐渐增加,激活能先增加,当晶化体积分数为14％时,激活能达到最大值379．4KJ／mol,然后随着晶化体积分数的逐渐增加,激活能减少。 相似文献