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排序方式: 共有5126条查询结果,搜索用时 16 毫秒
1.
《Journal of the European Ceramic Society》2022,42(14):6614-6623
Low-thermal conductivity ceramics play an indispensable role in maximizing the efficiency and durability of hot end components. Pyrochlore, particularly zirconate pyrochlore, is currently a highly promising and widely studied candidate for its extremely low thermal conductivity. However, there are still few pyrochlores that offer both stiffness, insulation, and good thermal expansion properties. In this work, the solidification method was innovatively introduced into the preparation of titanate pyrochlore, and combined it with the compositional design of high-entropy. Through careful composition design and solidification control, the high-density and uniform elements distributed high-entropy titanate pyrochlore ceramics were successfully prepared. These samples possess high hardness (15.88 GPa) and Young’s modulus (295.5 GPa), low thermal conductivity (0.947 W·m?1·K?1), excellent thermal expansion coefficient (11.6 ×10?6/K) and an exquisite balance between stiffness and insulation (E/κ, 312.1 GPa·W?1·m·K), in which the E/κ exhibits the highest value among the current reported works. 相似文献
2.
《中国有色金属学会会刊》2021,31(10):3063-3074
The transient liquid phase (TLP) bonding of CoCuFeMnNi high entropy alloy (HEA) was studied. The TLP bonding was performed using AWS BNi-2 interlayer at 1050 °C with the TLP bonding time of 20, 60, 180 and 240 min. The effect of bonding time on the joint microstructure was characterized by SEM and EDS. Microstructural results confirmed that complete isothermal solidification occurred approximately at 240 min of bonding time. For samples bonded at 20, 60 and 180 min, athermal solidification zone was formed in the bonding area which included Cr-rich boride and Mn3Si intermetallic compound. For all samples, the γ solid solution was formed in the isothermal solidification zone of the bonding zone. To evaluate the effect of TLP bonding time on mechanical properties of joints, the shear strength and micro-hardness of joints were measured. The results indicated a decrement of micro-hardness in the bonding zone and an increment of micro-hardness in the adjacent zone of joints. The minimum and maximum values of shear strength were 100 and 180 MPa for joints with the bonding time of 20 and 240 min, respectively. 相似文献
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The present study focused on the formation and crystallographic orientation of twinned dendrites coexisting with equiaxed grains in unidirectional solidification of Al-32%Zn (mass fraction) alloy. The morphology was investigated by optical metallograph and electron back-scattered diffraction technique. Results showed that the macrostructure of the alloy exhibited a typical feathery and fan-like structure while the microstructures were elongated lamellas, which were separated by coherent and incoherent twin boundaries. Both the primary trunk and all lateral arms of twinned dendrites grew along 〈110〉 directions, unlike regular 〈100〉 α(Al) dendrites. The facet growth of crystals at solid/liquid interface was responsible for the origin of twinned dendrites during the weak local convection, and high thermal gradient and medium solidification velocity had significant contribution to the formation of twinned dendrites. The formation mechanism of twinned dendrites which consisted of three multiplication ways of new twin boundaries formation and one way of dendrite evolution in twin plane was shown schematically. 相似文献
6.
Horizontal directional solidification experiments were carried out with a monophasic Sn-2%Sb (mass fraction) alloy to analyze the influence of solidification thermal parameters on the morphology and length scale of the microstructure. Continuous temperature measurements were made during solidification at different positions along the length of the casting and these temperature data were used to determine solidification thermal parameters, including the growth rate (VL) and the cooling rate (TR). High cooling rate cells and dendrites are shown to characterize the microstructure in different regions of the casting, with a reverse dendrite-to-cell transition occurring for TR>5.0 K/s. Cellular (lc) and primary dendrite arm spacings (l1) are determined along the length of the directionally-solidified casting. Experimental growth laws relating lc and l1 to VL and TR are proposed, and a comparative analysis with results from a vertical upward directional solidification experiment is carried out. The influence of morphology and length scale of the microstructure on microhardness is also analyzed. 相似文献
7.
Ismail Seçkin Çardaklı Ali Kalkanlı 《International Journal of Cast Metals Research》2019,32(3):145-153
In this study, as alternative methods to conventional production methods involving thin section copper permanent mould casting (fast solidification) and water atomization (rapid solidification) of AISI DC 53 cold work tool steel have been investigated. Thin slabs obtained by copper mould casting was homogenized at 1150 °C for one hour and then hot rolling was be applied. After hot rolling, conventional heat treatment have been applied to thin slabs. The same heat treatment procedure have been performed for a commercially available AISI DC 53 which is manufactured by thick section ingot casting and rolling. In order to investigate also the effect of rapid solidification on AISI DC 53 tool steel, steel powder was produced by water atomization technique. Experiments have revealed that thin steel slabs in permanent copper mould and rapidly solidified tool steel powder by water atomization have a more refined primary M7C3 carbides than commercially available steel. 相似文献
8.
摘要:TiN颗粒尺寸及其分布对耐蚀合金性能有明显的影响,因此有必要对TiN在铸坯中的分布及其析出行为进行研究。采用扫描电镜(SEM)、金相显微镜(OM)观察了TiN夹杂物在铸坯中的分布、尺寸及其形貌;基于热力学和动力学理论分析了耐蚀合金铸坯中TiN夹杂物的析出时机及其尺寸,结合试验结果和理论计算明确了TiN夹杂物在凝固后铸坯中的位置和尺寸与析出时机的关系,为控制TiN夹杂物提供理论指导。结果表明,冶炼过程中析出的TiN夹杂物尺寸较大,在凝固过程中被枝晶吞没,位于铸坯枝晶内和等轴晶内;微观偏析计算结果表明,在凝固分数为0.55时,TiN开始析出,最开始析出TiN夹杂物的逐渐长大,长大后的TiN易于被二次枝晶吞没,最终位于铸坯中的枝晶间和等轴晶内,后期析出的TiN则在枝晶间和等轴晶间。固相中析出的TiN夹杂物长大较慢,尺寸细小,最终位于奥氏体晶界。 相似文献
9.
Yun‐hui Wu Zhi‐fu Deng Ze‐fei Peng Rong‐min Zheng Shu‐qi Liu Shu‐ting Xing Jun‐yun Li De‐qun Huang Lan Liu 《Advanced functional materials》2019,29(36)
Low‐melting liquid metal is a hugely promising material for flexible conductive patterns due to its excellent conductivity and supercompliance, especially low‐cost and environmental liquid processing technology. However, the ever‐present fluidity characteristic greatly limits the stable shape and reliability of prepared liquid metal conductive electronics. Herein, a novel solidification strategy of liquid GaIn alloys by Ni doping and heat treatment is first reported, which can efficiently create a solid phase in the liquid metal and provide an effective solution for practical applications. Particularly, the liquid characteristic is preserved for conveniently fabricating different flexible electronic circuits, and then the solidification is carried out on prepared conductive patterns by heat treatment. The solidification mechanism is revealed by the interface chemical reaction between Ni and GaIn, creating the solid phase of intermetallic compound (Ga4Ni3 and InNi3) during heat treatment. Moreover, a biphasic GaInNi can be obtained by regulating the atomic ratio of gallium, indium, and nickel. As a result, the obtained GaInNi possesses extremely low sheet resistance (15 ± 4.5 to 135 ± 2.5 mΩ sq?1) and the variation of ΔR/R0 exhibits low level (0–2) when strained up to 100%, which offers a promising strategy to prepare stretchable and reliable liquid metal electronics. 相似文献
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