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81.
W.J. Zong Z.Q. Li T. Sun D. Li K. Cheng 《Journal of Materials Processing Technology》2010,210(6-7):858-867
In this work, the dynamic micro-mechanical strengths of diamond crystal are deduced in theory, including the tensile, shearing and compressive strengths. The calculated results reveal that the dynamic micro-mechanical strengths have great anisotropy, but the tensile strengths are less than the shearing and compressive ones in any orientation of any plane. Subsequently, a novel evaluation factor is proposed, which integrates from the theoretical tensile strength in the orientation of flank face paralleling to the cutting direction and the theoretical tensile strength in the orientation of rake face paralleling to the chip flowing direction. And then as expected, the anisotropy of the resistance to wear of diamond cutting tools can be predicted exactly through comparing the evaluation factor. Theoretical analyses indicate the larger the evaluation factor, the greater the wear resistance of diamond cutting tool is. Finally, the cutting experiments are carried out on the (1 1 1) silicon wafers, and the sampled data are well consistent with the theoretical predictions, which validates that the proposed evaluation factor is suited for predicting the anisotropy of the resistance to wear of diamond cutting tools. 相似文献
82.
热带钢连轧机工作辊下机后尚未完全冷却即进行磨削,残存的不均匀热变形导致磨削的工作辊辊形在空冷一段时间上机时很难达到工艺设定值.针对热辊形不易测量的特点,制定合理的物理测量方式,准确地测量了工作辊下机后的温度分布和热辊形.考虑复杂的工作辊换热边界条件,采用有限差分法对工作辊空冷时的温度场和热变形进行了数值模拟,计算结果与测试结果吻合良好.对工作辊下机后不同时刻的热变形进行仿真,通过将目标上机辊形和磨削时热辊形叠加来设定磨削辊形,为实现合理的辊形磨削提供了依据和计算方法. 相似文献
83.
以硼酸和三聚氰胺为原料,采用化学法制备了乱层石墨结构的B-C-N化合物.在5.5GPa、800~1500℃条件下对该化合物进行了高温高压处理.采用X射线衍射(XRD)、透射电子显微镜(TEM)以及电子能量损失谱(EELS)对所制备的样品进行了结构、形貌和成分分析.研究结果表明:在5.5GPa压力下,随着温度的升高,B-C-N化合物逐渐由乱层石墨结构转变为六方结构,在1200℃时,得到了结晶较好的六方B-C-N化合物,同时样品中含有少量的六方BN和非晶C.当温度高于1400℃,B-C-N化合物完全分解成六方BN和石墨. 相似文献
84.
《Materials Characterization》2007,58(10):941-946
The hot deformation characteristics of a Ni-based superalloy were studied in the temperature range 1050–1180 °C and strain rate range 0.01–10 s− 1 using hot compression tests. Processing maps for hot working were developed on the basis of the variations of efficiency of power dissipation with temperature and strain rate, interpreted using a dynamic materials model. A hot deformation equation is given to characterize the dependence of peak stress on the temperature and strain rate. A hot deformation apparent activation energy of the Ni-based superalloy is about 496 kJ/mol. The processing maps of the Ni-based superalloy obtained in a strain range of 0.1–0.7 are essentially similar, which indicates that strain does not have a significant influence. The maps exhibit a clear domain with its peak efficiency at about 1140 °C and 0.01 s− 1; the domain has its peak efficiency of about 36–41% for different strains. On the basis of hot deformation microstructural observations, the full recrystallization region can be identified in the processing map at a strain of 0.7. 相似文献
85.
《Materials Science and Engineering: A》2007,443(1-2):224-228
Mechanical properties of TiCP/LY12 Al-based composites prepared by an in situ synthesis method were studied. The micro-structure, morphology, and distribution of TiCp particles in the LY12 Al alloy matrix were also investigated by XRD, SEM, and HRTEM. The phase composition of the TiCP/LY12 composites, interfacial structure of TiC particle-to-particle and TiC particle-to-Al matrix, and structure of triple phase among TiC particle, Al2Cu phase, and Al matrix were also studied. There are no detectable Al3Ti phases in TiCP/LY12 composites, and a strong cohesive interface between TiC particles and Al-based alloy matrix was observed in the in situ synthesized TiCP/LY12 composites. After heat treatment using T6 procedure, it was found that ultimate strength (σb), yield strength (σs), and Young's modulus (E) of TiCP/LY12 composites increased but the elongation ratio decreased with increasing of the mass fraction of TiC particles. 相似文献
86.
AbstractIn order to develop a flame retardant using the phosphazene derivative of a natural polymer, hexachlorocyclotriphosphazene and collagen were used as the raw materials to synthesize collagencoclotriphosphazene. The Fourier transform infrared results indicate that flame retardant collagencoclotriphosphazene(CGCP) was successfully synthesized. Thermal properties of CGCP were evaluated using thermogravimetry. The thermal analysis shows that the introduction of phosphazene into collagen lowered the primary decomposition temperature, increased the decomposition rate, and caused less weight loss. The viscose fibers blended by CGCP were prepared by the wet spinning method, and the properties of the fiber were investigated. Limiting oxygen index of the flame-retardant fiber containing 12% CGCP was 28.3%, which increased greatly comparing to the fiber sample without CGCP and just decreased slightly to 27.6% after 30 washing cycles. The thermal analysis shows that the introduction of CGCP increased the decomposition rate of viscose fiber at a lower temperature, and caused less weight loss. After burning, the scanning electron microscopy image showed an inflated carbonized coat on the fiber surface. The effect of CGCP on the mechanical properties of the fibers was insignificant. CGCP was compatible with cellulose, and the flame retardancy of the viscose fiber was significantly improved. Due to the introduction of CGCP, moisture regain of the fiber is a little higher than that of viscose fiber. 相似文献
87.
Gold Nanoshells: Combined Near Infrared Photothermal Therapy and Chemotherapy Using Gold Nanoshells Coated Liposomes to Enhance Antitumor Effect (Small 30/2016)
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88.
A series of Fe–Mo–C steels with Mo addition from 0.1 to 0.8 wt.% have been prepared to study the effects of Mo on high-temperature strength of fire-resistant steel. The high-temperature hardness tests were carried out to investigate the strengthening mechanisms of Mo in fire-resistant steel. The results show that the hardness of Fe–Mo–C steels increases with the increase of Mo content at a given temperature, and the strengthening effect of Mo becomes remarkable when the temperature is on the rise. Theoretical analysis indicates that the solid-solution strengthening of Mo is the dominant high-temperature strengthening mechanism in fire-resistant steel, but this strengthening effect becomes relatively weak when Mo content is more than or equal to 0.5 wt.%. Moreover, the bainite strengthening plays an important role in improving the high-temperature strength of fire-resistant steel. Furthermore, the analysis indicates that the ferrite grain size has less effect on high-temperature strength of fire-resistant steel. The present results also provide fundamentals to design low-cost fire-resistant steels with excellent high-temperature properties and the most reasonable range of Mo addition is 0.2–0.3 wt.%. 相似文献
89.
The objective of this study is to develop a hot diffusion-compression bonding process for cladding low carbon steel (LCS) to high chromium cast iron (HCCI) in solid-state. The influence of temperature (950–1150 °C) and strain rate (0.001–1 s−1) on microstructure, hardness and bond strength of the HCCI/LCS bimetal were investigated. The interface microstructure reveals that the unbonded region can only be found for 950 °C due to lack of diffusion, while the intergrowth between the constituent metals occurred at and above 1100 °C. When bonding temperature increases to 1150 °C, a carbide-free zone was observed near the interface on the HCCI layer, and the thickness of the zone decreases with an increase of bonding strain rate. These evolutions indicate that the bond quality was improved by raising temperature and reducing strain rate due to the increase of element diffusion. The hot compression process of the bonding treatment not only changes the carbide orientation of the HCCI, but also increases the volume fraction of Cr–carbide. Based on the microstructural examinations and mechanical tests, the optimum bonding temperature and bonding strain rate are determined to be 1150 °C and 0.001 s−1, respectively. 相似文献
90.
Atmospheric pressure microplasma was produced in a scanning electron microscope (SEM) chamber for synthesising carbon nanomaterials. The SEM observation is convenient for both adjusting the gap length and observing the electrode surface before and after experiments. After adjusting the gap length, the electrodes were housed in a small removable gas cell equipped in the SEM chamber and CH4 discharge gas was introduced into the gas cell. It was found that the discharge was pulsated automatically because of slow discharge through a large ballast resistor and fast discharge through gas breakdown, even though a DC voltage was applied. The peak pulse current density was almost 60 kA/cm2, the peak power density in the microplasma volume was approximately 555 MW/cm3 and the pulse width was 10 ns typically. Spherical and nanotube-like carbon nanomaterials were found on the cathode surface after microplasma discharge for 1? 5 s.With the discharge time increasing, the spherical substance changes into nanotube-like carbon nanomaterials. 相似文献