检索结果-南通市图书馆

Journal of Materials Science & Technology 2023年第36期167卷 205-212页

作者： Zhangtian Wu Wei Ji Jinyong Zhang Yanan Yuan Ji Zou Weimin Wang Zhengyi Fu State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China Hubei Longzhong Laboratory Wuhan University of Technology Xiangyang Demonstration ZoneXiangyang 441000China

As an important A_(2)B_(2)O_(7)-type ceramic,(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)high-entropy pyrochlore pos-sesses promising properties such as high melting point,high chemical durability,and low thermal conductivity.However,the low sintering ability limits its application in thermal barrier coating and radioactive waste immobilization.It usually needs long-term high-temperature soaking to achieve full density,but with inevitable grain growth.In this work,dense and grain-refined nanocrystalline(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)ceramics were prepared with ultra-high pressure sintering(UHPS)method under 10 GPa at a low temperature of 800℃.The densification behavior,microstructure evo-lution,and properties of the UHPS-ed samples were then investigated.The grain size of as-prepared(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)ceramic was only 151 nm,which is 40%smaller than that of raw pow-der.In addition,it exhibited advantageous properties including both high hardness and aqueous durabil-ity.Plastic deformation under ultra-high pressure was believed as the dominant densification mechanism responsible for grain refinement and property improvement.

关键词： High-entropy ceramics Ultra-high pressure sintering grain refining Nanocrystalline Plastic deformation

In situ radiographic study of the grain refining behavior of Al_(3)Sc during the solidification of Al-10Cu alloy

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第27期122卷 33-43页

作者： Yue Wu Yang Tang Ya Zhang Yanan Fu Hui Xing Jiao Zhang Jun Jiang Baode Sun Shanghai Key Lab of Advanced High-Temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240PR China Shanghai Synchrotron Radiation Facility Shanghai Institute of Applied PhysicsCASShanghai 201204PR China State Key Lab of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai 200240PR China Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai Jiao Tong UniversityShanghai 200240PR China Mechanical Engineering Department Imperial College LondonLondon SW72AZUK

grain refinement of Al alloys inoculated by rare earth elements,such as Sc,has been extensively acknowledged,while the practical behavior of how inoculant Al_(3)Sc particles affect the refinement in solidification has not been clarified due to the non-transparency of the solidification process.Here,the microstructural evolution of primary Al_(3)Sc particles andα-Al grains in Al-10 wt.%Cu alloy solidifications with 0.2 wt.%,0.6 wt.%,and 1.0 wt.%Sc additions was investigated by in situ synchrotron X-ray radiography.The detailed mechanisms of curve motion of grains(CMG)and melt convection were revealed.The efficient grains nucleation,uniformly scattered small initial grains,and long duration of melt convection contributed to the best refinement in the 0.6 wt.%Sc addition sample.This work provides a deep insight into grain refinement in solidification with Sc addition,which will enlighten the composition design and casting process of Al alloys inoculated by rare earth elements.

关键词： Radiography Solidification Melt convection Curve motion of grains grain refining

grain refining and property improvement of AZ31 Mg alloy by hot rolling

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2009年第S2期19卷 326-330页

作者：苗青胡连喜孙宏飞王尔德 School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

Hot rolling of AZ31 Mg alloy was performed by using as-cast alloy ingot as the starting material.The microstructures and mechanical properties of the as-rolled alloy subjected to various rolling passes were investigated.The results show that the grain size of the alloy can be refined steadily with increasing rolling passes by dynamic recrystallization.With the steady refining of the grain size,both the mechanical strength and the plasticity of the alloy are improved correspondingly.In particular,when the grain size is reduced to about 5μm after 5 rolling passes,the yield strength,ultimate tensile strength and tensile fracture strain of the alloy are 211 MPa,280 MPa and 0.28 in the transverse direction,they are 200 MPa,268 MPa and 0.32 in the rolling direction,respectively.

关键词： AZ31 Mg alloy hot rolling grain refining mechanical properties

Heat transfer and grain refining mechanism during melt treatment by cooling sloping plate

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2012年第4期25卷 320-328页

作者： Renguo GUAN Zhanyong ZHAO Runze CHAO Hongqian HUANG Chunming LIU College of Materials and Metallurgy Northeastern UniversityShenyang 110819China

Heat transfer of flow melt and grain refining mechanism during melt treatment by the cooling sloping plate were investigated. The results show that the cooling sloping plate can refine not only grains of alloys but also can obviously refine pure metal. Cooling ability of the plate is the key factor that induces grain refining, the plate material and the flow amount can affect cooling rate of the melt and thus affect refining effectiveness. The cooling rate of the melt on the cooling sloping plate is much faster than that of the conventional casting process, which can reach 1000 K/s and belongs to meta-rapid solidification scope. The thickness of the temperature boundary layer is much larger than that of the velocity boundary layer on the sloping plate, but the temperature gradient is small in the temperature boundary layer. Under strong cooling action by the cooling plate, most parts of the melt on the plate surface can form undercooling, which causes continuous eruptive nucleation, this is the main grain refining mechanism, and the heterogeneous nucleation on the plate surface is a helpful supplement for the nucleation.

关键词： grain refining Nucleation Cooling rate Sloping plate Temper-ature boundary layer

Effect of ECAE Preheating on grain refining of Nickel-Titanium Alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2004年第S1期22卷 164-166页

作者：向国权吴炬程先华 School of Mechanical and Power Engineering Shanghai Jiaotong University Shanghai 200030 China

The influence of equal channel angular extrusion preheating on the microstructure of NiTi was examined. Temperatures under non-isothermal condition is 750, 850 and 950 ℃, and ram speed was 25 mm·s^(-1). The micrographs showed that processing by each of the three temperatures via ECAE can refine the initial coarse grains of NiTi (as-received) after the first pass, and the developments of microstructure were quite different under different hot-working conditions. The influence of ECAE preheating (including temperature and time) on the microstructure of nickel-titanium was analyzed.

关键词： preheating NiTi alloy ECAE grain refining

A review:Past,present and future of grain refining of magnesium castings

在线全文

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2019年第3期7卷 355-369页

作者： Erdem Karakulak BCAST Brunei University LondonUxbridgeMiddlesex UB83PHUK

Magnesium is the lightest constructional metal,which makes it an important material for different applications like automotive,transportation,aviation and aerospace.There are several studies about developing properties of existing Mg alloys and introducing new alloy systems to industrial producers.An important way to improve properties of metallic materials is to decrease grain size that results almost in increasing all kind of properties of the material.This review paper aims to summarize the literature about grain refining of magnesium alloys.The text is consisting of three sections,which focused on the(1)grain refining methods used in the past,which are not used today,(2)grain refining methods currently being used in the industry and(3)novel and newly developed methods that may find usage in the industry in future.Before explaining grain refining methods of magnesium alloys a general summary about grain refinement of metals is also provided.

关键词： Magnesium Casting grain refining grain size.

EFFECT OF grain refining ON FATIGUE-CREEP INTERACTION BEHAVIOURIN A Ni-BASE SUPERALLOY

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 1989年第1期2卷 47-50页

作者： YANG Wangyue ZHA NG Jishan CHEN Guoliang Beijing University of Science and Technology,Beijing,ChinaTIAN Shusen GENG Qingquan Fushun Steel Works,Fushun,Liaoning,China

The fatigue-creep interaction behaviour of superalloy GH698 with different grain sizes has been studied at 700℃.The results show that three zones,F,C and FC,can be distinguished at the fatigue-creep interaction curves.In zones FC and C,the presence of alternative stresses inhibits the creep deformation process therefore delays the fracture of the alloy.This effect will be enhanced by grain refining.However,in zone F,grain refining exhibits an inverse ef fect under large alternative stresses.

关键词： Ni-base alloy GH698 grain refining fatigue creep

Microstructure and mechanical properties of Ti44Al6Nb alloys with different cerium contents

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2020年第4期39卷 402-407页

作者： Hong-Ze Fang Rui-Run Chen Xiao-Yu Chen Zhi-Kun Ma Hong-Sheng Ding Jing-Jie Guo School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Department of Tank Repair People's Liberation Army Armored Force Engineering InstituteChangchun 130117China

Ti44A16 Nb-based alloy ingots with different cerium(Ce)contents(0,0.05,0.10,0.15,0.20;at%)were prepared by non-consumable vacuum arc smelting furnace(WK-Ⅱ).The surface quality,macrostructure,microstructure,compressive properties and fracture morphology of these ingots were studied.The results show that Ce has few influences on the surface quality.Ce can refine grain size and the average grain size decreases from 0.50 to 0.19 mm with the increase of Ce content.Meanwhile,the microstructure morphology of these ingots changes from large lamellar microstructure to dual-phase microstructure.With addition of Ce,CeO and AlCe3 are formed during melting and solidifying,which act as the core of heterogeneous nucleation and refine the grain.The compressive testing results show that Ce can improve strength and ductility.The ultimate compressive strength increases from 1156.2 to 1472.2 MPa with Ce content increasing from 0 at%to 0.20 at%.The compression ratio is improved from 10.2%to 15.3%with Ce content increasing from 0 at%to 0.10 at%.The refined crystalline strengthening and grain boundary strengthening are the main reasons for the improvement of compressive property.

关键词： Ce TiAl alloy Compressive property grain refining

Microstructure, hardness and contact fatigue properties of X30N high nitrogen stainless bearing steel

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research(International) 2018年第9期25卷 954-967页

作者： Hai-feng Xu Gui-lin Wu Chang Wang Jian Li Wen-quan Cao Special Steel Institute Central Iron and Steel Research Institute Beijing 100081 China College of Materials Science and Engineering Chongqing University Chongqing 400045 China Central Laboratory Central Iron and Steel Research InstituteBeijing 100081 China Center for Fuel Cell Innovation State Key Laboratory of Material Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan 430074 Hubei China

Microstructure, hardness and fatigue properties of X30N high nitrogen stainless bearing steel were investigated. It was found that nitrogen addition could effectively reduce the amount and size of coarse carbides. The original austenite grain size was obviously refined. Additionally, more retained austenite was found in X30N steel after quenching at 1050 ℃, which could be reduced from about 30% to about 6% by cold treatment at - 73 ℃ and subsequent tempering, and thus, the ultimate hardness was increased up to about 61 HRC with reduction of austenite and precipitation of carbonitrides. Furthermore, the rolling contact fatigue lives of X30N steel ate superior to those of 440C steel, which was attributed to the enhanced hardness and a certain retained austenite in the high nitrogen steel.

关键词： Nitrogen addition grain refining High hardness Ultrafine precipitate Contact fatigue life High nitrogen stainless bearing steel

Effect of Ultrasonic Output Power on refining the Crystal Structures of Ingots and Its Experimental Simulation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2005年第1期21卷 47-52页

作者： dunwenLI TadashiMOMONO DepartmentofMaterialsScienceandEngineering LiaoningInstituteofTechnologyJinzhou121001China//GraduateSchoolMuroranInstituteofTechnologyMuroran050-8585Japan FacultyofEngineering MuroranInstituteofTechnologyMuroran050-8585Japan

In this study, a series of tests were conducted by using aluminum-based alloy to determine the formation of grain refining structure based on the ultrasonic vibration (UV). Furthermore, the simulation test and effect of ultrasonic output power were studied using ammonium chloride. Finally, the mechanism of grain refinement was investigated. The results show that: (1) By applying the UV to aluminum-base alloy, the grain refining rate of ingots tended to increase with the increase of the output value of UV. (2) It was confirmed that time from after the pour to the beginning of crystallization as well as cloudiness tended to decrease with increasing the ultrasonic power value of UV. Moreover, it can be seen from each cooling curve that a uniform temperature gradient existed in the melt as the power of UV increased, that made the melt strongly stirred. (3) It was also considered that the grain refining effect of ingots, which was observed from the simulation tests, resulted from nucleation action and stirring division action by applying the UV.

关键词： Aluminum alloy grain refining Ultrasonic vibration Simulation