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Diffusion behavior of Nb element in high Nb containing TiAl Alloys by reactive hot pressing

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Rare Metals 2006年第4期25卷 349-354页

作者： WANG Yanhang LIN Junpin HE Yuehui WANG Yanli CHEN Guoliang State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China State Key Laboratory for Powder Metallurgy Central South University Changsha 410083 China

Diffusion behavior of Nb in elemental powder metallurgy high Nb containing TiAl alloys was investigated. The results show that Nb element dissolves into the matrix by diffusion. Pore nests are formed in situ after Nb diffusion. With the increase in hot pressing temperature, the diffusion of Nb will be more sufficient, and the microstructure is more homogeneous. Nb element diffuses completely at 1400℃. Meanwhile, compression deformation and agglomeration phenomena of pores are observed in some pore nests. hot isostatic pressing （HIP） treatment can only efficiently decrease but not eliminate porosity completely.

关键词： powder metallurgy TiAl-based alloy hot pressing diffusion hot isostatic pressing

Comparative study of β-Si_3N_4 powders prepared by SHS sintered by spark plasma sintering and hot pressing

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Journal of University of Science and Technology Beijing 2007年第3期14卷 271-275页

作者： Ling Bai Xiaodong Mao Weiping Shen Changchun Ge Laboratory of Special Ceramics and Powder Metallurgy University of Science and Technology Beijing Beijing 100083 China

β-Si3N4 powders prepared by self-propagating high-temperature synthesis （SHS） with additions of Y2O3 and Al2O3 were sintered by spark plasma sintering （SPS）. The densification, microstructure, and mechanical properties of Si3N4 ceramics prepared using this method were compared with those obtained by hot pressing process. Well densified Si3N4 ceramics with finer and homogeneous microstructure and better mechanical properties were obtained in the case of the SPS technique at 200°C lower than that of hot pressing. The microhardness is 15.72 GPa, the bending strength is 716.46 MPa, and the fracture toughness is 7.03 MPa·m1/2.

关键词： self-propagating high-temperature synthesis （SHS） hot pressing spark plasma sintering （SPS） silicon nitride mechanicalproperties

Microstructure and mechanical properties of Cu-B4C and CuAl-B4C composites produced by hot pressing

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Rare Metals 2019年第12期38卷 1169-1177页

作者： Zulkuf Balalan Furkan Gulan Mechanical Engineering Department Faculty of Engineering and ArchitectureUniversity of Bingol

Cu matrix composite materials reinforced with B4C particle at four different contents(1.5 wt%,3.0 wt%,4.5 wt% and 6.0 wt%) and also CuAl matrix composites with 13 wt% Al reinforced with B4C particle at four different contents(1.5 wt%,3.0 wt%,4.5 wt% and 6.0 wt%)were fabricated by hot pressing(HP) and a powder metallurgy(PM) process.Experimental samples were produced by keeping them at 880℃ at the constant pressure of 2.3×10~8 Pa for 6 min.The density,microstructure and mechanical properties of the produced samples were examined.The microstructure and phase examinations were carried out by scanning electron microscope(SEM)and optical microscope(OM),energy-dispersive spectrometer(EDS) and X-ray diffractometer(XRD) analysis.The hardness measurements,three-point bending test and impact test were conducted to determine the mechanical properties.As a result of the examinations,it was observed that the relative density values decreased with the increasing content of B4C and provided a relatively effective bonding.Moreover,it was homogeneously distributed in the produced specimens.Consequently,there was a considerable increase in the hardness and the bending strength of CuAl matrix specimens with Al addition.

关键词： Boron carbide hot pressing Mechanical properties Aluminum

Microstructure and thermoelectric properties of Bi_(0.5)Na_(0.02)Sb_(1.48-x)In_xTe_3 alloys fabricated by vacuum melting and hot pressing

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Rare Metals 2015年第11期34卷 770-775页

作者： Xing-Kai Duan Kong-Gang Hu Da-Hu Ma Wang-Nian Zhang Yue-Zhen Jiang Shu-Chao Guo Center for New Energy Materials Research School of Mechanical and Materials Engineering Jiujiang University

The Bi0.5Na0.02Sb1.48-xInxTe3alloys（x =0.02-0.20） were synthesized by vacuum melting and hot pressing methods at 753 K,60 MPa for 30 min.Effects of Na and In dual partial substitutions for Sb on the thermoelectric properties were investigated from 300 to 500 K.Substituting Sb with Na and In can enhance the Seebeck coefficient effectively near room temperature.The electrical resistivity of the Na and In dual-doping samples is higher within the whole test temperature range.The Bi0.5Na0.02Sb1.48-xInxTe3samples（x = 0.02,0.06） play a great role in optimizing the thermal conductivity.As for the Bi0.5Na0.02Sb1.46In0.02Te3alloy,the minimum value of thermal conductivity reaches 0.53 W·m-1·K-1at 320 K.The thermoelectric performance of the Na and In dualdoped samples is greatly improved,and a figure of merit ZT of 1.26 is achieved at 300 K for the Bi0.5Na0.02Sb1.42In0.06Te3,representing 26%enhancement with respect to ZT = 1.0 of the undoped sample.

关键词： Microstructure Dual doping hot pressing Thermal co

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing

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Journal of University of Science and Technology Beijing 2007年第3期14卷 251-255页

作者： Yanhang Wang Junpin Lin Yuehui He Yanli Wang Guoliang Chen State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China State Key Laboratory for Powder Metallurgy Central South University Changsha 410083 China

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing was investigated. The results showed that the density of the sample hot pressed at 1400°C could reach a near full density of 98.37%. However, the densification abnormality was observed at 1500°C. The diffusion of elemental Nb during microstructural evolution is an important aspect affecting densification, which will form pore nests. With the increase of hot pressing temperature, the diffusion of Nb becomes more adequate. HIP （hot isostatic pressing） treatment can only decrease porosity to some extent, but cannot eliminate it completely.

关键词： TiAl based alloy powder metallurgy densification hot pressing

Structure and magnetic properties of bulk nanocrystalline Nd-Fe-B permanent magnets prepared by hot pressing and hot deformation

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Journal of Rare Earths 2013年第7期31卷 674-678页

作者：宋杰岳明左建华张子瑞刘卫强张东涛张久兴郭朝晖李卫 College of Materials Science and Engineering Beijing University of Technology Division of Functional Materials Central Iron and Steel Research Institute

Structure and magnetic properties were studied for bulk nanocrystalline Nd-Fe-B permanent magnets that were prepared at 650 ℃ for 3 min under 300 MPa using the SPS-3.20-MK-V sintering machine and the hot pressed magnets were then submitted to hot deformation with height reduction of 50%, 60%, 70%, 80%, and 85%. Effects of height reduction （HR） and deformation temperature on the structure and magnetic properties of the magnets were investigated. The crystal structure was evaluated by means of X-ray diffraction （XRD） and the microstructure was observed by transmission electron microscopy （TEM）. The magnetic properties of the magnets were investigated by vibrating sample magnetometer （VSM）. As the height reduction increased, the remanence （Br） of the magnets increased first, peaks at 1.3 T with HR=60%, then decreased again, and the coercivity （Hci） of the magnets decreased monotonically. On the other hand, as the deformation temperature increased, the Br of the magnets increased first, peaks at 1.36 T with HR=60%, then decreased again, and the H^i of the magnets decreased monotonically. Under optimal conditions, the hot deformed magnet possessed excellent magnetic properties as Brl.36 T, Hci=1143 kA/m, and （BH）max=370 kJ/m3, suggesting the good potential of the magnets in practical applications.

关键词： nanocrystalline Nd-Fe-B magnets hot pressing hot deformation microstructure magnetic properties rare earths

Effect of hot pressing on Microstructure and Mechanical Properties of Bulk Nanocrystalline Fe_3Al Materials Containing Manganese Element

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Journal of Iron and Steel Research(International) 2011年第3期18卷 65-71页

作者： LI Yu-feng LA Pei-qing WEI Yu-peng LU Yang YANG Yang State Key Laboratory of Gansu Advanced Nonferrous Materials Lanzhou University of TechnologyLanzhou 730050GansuChina

Bulk nanocrystalline Fe3Al materials containing manganese of 10% were prepared by aluminothermic reaction.hot pressing of those materials was performed at different temperatures and times.The microstructures of the alloy were investigated by optical microscope（OM） and electron probe microanalyzer（EPMA）.The grain sizes of the materials were analyzed by X-ray diffraction（XRD） and transmission electron microscope（TEM）.The results showed that the grain sizes of the materials increase after hot pressing.The grain sizes of the materials decrease with increasing the hot pressing times at the same temperature and the grain sizes of the materials increase with increasing hot pressing temperatures at identical times.The hardness and compressibility of the materials were also tested.The results showed that the hardness decreases with increasing hot pressing times at 800 ℃ and hardness increases with increasing the hot pressing temperatures.The variation of hardness with grain size of the nanocrystalline Fe3Al materials after hot pressing is contrary to the Hall-Petch relation.The materials are not broken during hot pressing and exhibit good plasticity and compressibility.

关键词： hot pressing Fe3Al nanostructure material microstructure mechanical property

Zn_(1-x)Co_xO Diluted Magnetic Semiconductor Bulk Prepared by hot pressing

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Journal of Wuhan University of Technology(Materials Science) 2010年第3期25卷 527-529页

作者：林文松 School of Materials Engineering Shanghai University of Engineering Science

Zn1-xCoxO diluted magnetic semiconductor bulks were prepared by hot pressing.Mixed powders of pure ZnO and CoO were compacted under pressure of 10 MPa at the temperature of 1 073 K.Then the samples were annealed in vacuum at the temperature from 673 K to 873 K for 10 h.The crystal structure and magnetic properties of Zn1-xCoxO bulks have been investigated by X-ray diffraction（XRD） and vibrating sample magnetometer（VSM）.X-ray photoelectron spectroscopy（XPS） was used to study chemical valence of zinc and cobalt in the samples.The results showed that Zn1-xCoxO samples had c-axis oriented wurtzite symmetry,neither cobalt or cobalt oxide phase was found in the samples if x was less than 0.15.Zn and Co existed in Zn0.9Co0.1O sample in Zn2＋ and Co2＋ states.The results of VSM experiment proved the room temperature ferromagnetic properties（RTFP） of Co-doped ZnO samples.The saturation magnetization and the coercivity of Zn0.9Co0.1O sample,observed in the M-H curve,were about 0.20 emu/g and 200 Oe,respectively.

关键词： hot pressing diluted magnetic semiconductors Zn1-xCoxO

Porous bulk metallic glass fabricated by powder hot pressing

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International Journal of Minerals,Metallurgy and Materials 2007年第S1期15卷 59-63页

作者： Keqiang Qiu1), Bo Yu2), and Yinglei Ren1) 1) School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110023, China 2) Shenyang Research Institute of Foundry, Shenyang 110022, China

A synthesis method for the production of porous bulk metallic glass (BMG) was introduced. This method utilizes the su- perplastic forming ability of amorphous powder in the supercooled liquid (SCL) state and intenerating salt mixture as a placeholder to produce BMG foam by using a hot die pressing method. Scanning electron microscope (SEM), X-ray diffraction (XRD) and dif- ferential scanning calorimetry (DSC) were employed to characterize the morphologies of foaming structure, the crystallization and the percentage of crystallization of the as-produced porous BMG. The results suggested that the formation of porous structure by su- perplastic forming process is feasible. Good bonding effect was observed between amorphous powder particles. Less than 6.5% of crystalline phases were formed during hot pressing, and less than 5.5% of residual salt was enclosed in the foam. To remove any re- sidual salt particles, salt preforms with three-dimensional network and good connectivity is necessary.

关键词： porous bulk metallic glass hot pressing placeholders superplastic forming