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利用回转振动粘度仪在液相线以上较大温度范围内,测量了In-55%Sb(质量分数)亚共晶合金熔体在不同的升降温过程中的粘度.实验结果表明,熔体经历的热历史对其粘度具有显著的影响.熔体在降温过程中的粘度高于升温过程中,在过热100℃后的降温过程中熔体的粘度较之无过热的降温过程中要低.在不同的热过程中,粘度发生转折变化的温度不同,在升温过程中,发生在850℃左右,在过热100℃和无过热的降温过程中,分别发生在750℃和650℃左右.熔体粘度的突变反映了熔体结构在相应温度的突然变化. 相似文献
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利用扫描电镜和金相显微镜等手段,研究了浇注温度和冷却速度对Al—Cu合金组织的影响。结果发现,在Cu质量分数含量为5.65%的合金组织中出现了共晶组织,并随着浇注温度的升高,共晶组织体积分数明显增加。这是因为在Al—cu合金熔体中存在着Al原子集团,随着熔体温度的升高,原子集团尺寸减小。而且发现随着冷却速度的减小,同一浇注温度下的同成分的合金组织中共晶组织体积分数减小,共晶层片间距的分布由集中变分散。 相似文献
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Bi-20.5Te合金熔体结构转变及其对凝固的影响 总被引:4,自引:4,他引:0
通过对Bi-20.5Te合金熔体电阻率随温度变化的研究,发现合金熔体在642℃时存在着液一液结构转变。分析Bi-Te合金熔体在不同成分和不同温度的原子结合规律,认为这种结构转变是由于熔体中的原子团簇变化引起的。将Bi-20.5Te合金分别在熔体结构转变前温度(600℃)、结构转变后温度(700℃)的范围内熔炼、保温,测定相应的凝固曲线,并观察凝固组织。结果表明,相对于在结构转变前保温处理的熔体,将合金在700℃保温处理后,凝固时所需过冷度增大,释放凝固潜热更加剧烈,并且凝固组织显著细化。产生这种现象的原因是由于熔体结构内的Bi—Bi同类原子团簇,以及具有共价结合的Bi—Te原子团簇在高温下被打破,熔体趋向均匀,对凝固过程中的原子扩散造成影响,进而影响合金的凝固行为及组织。 相似文献
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利用熔体黏度仪系统研究了不同成分Ga-Sb熔体的黏度变化规律。结果表明,Ga-Sb熔体的黏度总体趋势是随温度的降低而增大,黏度变化曲线基本呈指数变化。其中Ga36.5Sb63.5熔体黏度随温度的变化在830℃左右出现突变,将黏度曲线分成低温区和高温区两部分。根据该熔体结构变化的特点,对有关试验结果进行了分析讨论。 相似文献
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利用熔体粘度测试、X射线衍射分析、高温DSC分析等方法,研究了Al84Mg10Ce6合金的熔体粘度随温度变化的规律,结合薄带的非晶形成能力,分析了合金熔体不同过热温度与其非晶形成能力的相关性.结果表明,Ce元素的加入使得Al84Mg10Ce6熔体产生了结构突变,增强了铝基合金非晶形成能力,Al-Mg系合金非晶形成能力与其熔体温度之间具有相关性,850 ℃熔体通过熔甩工艺制得非晶态薄带. 相似文献
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分别在750、850、950和1050℃下,研究熔体过热处理对Al-4.7%Cu(质量分数)合金定向凝固组织的影响,利用综合热分析仪测定Al-4.7%Cu合金熔体结构特征及变化过程。结果表明:经过950℃和1050℃过热处理的一次枝晶间距比在750℃常规过热直接定向凝固的分别减小了31.2%和36.2%;随着熔体过热时间的延长,一次枝晶间距减小,组织越来越细密;但随着低温保持时间的延长,一次枝晶间距增大,组织越来越粗大,表明熔体高温处理对定向凝固组织形态的影响逐渐衰退;熔体过热处理对Al-4.7%Cu合金定向凝固组织有显著影响的原因在于熔体过热处理改变了熔体结构状态。 相似文献
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Deng-Kui Zhang Guo-Qing Wang Ai-Ping Wu Ji-Guo Shan Yue Zhao Tian-Yi Zhao Dan-Yang Meng Jian-Ling Song Zhong-Ping Zhang 《金属学报(英文版)》2019,32(6):684-694
In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone. 相似文献
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After nearly two years'tense construction the first phase of industrialized base of Shenyang Research Institute of Foundry 《中国铸造》2008,5(1):63-64
After nearly two years' tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry (SRIF), located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation. 相似文献
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Z. Sun S.L. Zheng Y. Zhang 《金属学报(英文版)》2007,20(3):187-192
Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process. 相似文献
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R. González-Martínez 《金属学报(英文版)》2007,20(4):235-240
The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke. 相似文献
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The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C). 相似文献
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The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel. 相似文献
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This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before. 相似文献
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Chao Yang He-Fei Huang Massey de los Reyes Long Yan Xing-Tai Zhou Tian Xia De-Liang Zhang 《金属学报(英文版)》2015,28(7):809
Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties. 相似文献
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Lei Li Bo Xu Wei-Ping Tong Hui Zhang Chun-Yan Ban Li-Zi He Zhi-Hao Zhao Yu-Bo Zuo Qing-Feng Zhu Jian-Zhong Cui 《金属学报(英文版)》2015,28(6):725
A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed. 相似文献
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综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。 相似文献