Microwave sintering of W-15Cu ultrafine composite powder prepared by spray drying &; calcining-continuous reduction technology

The effects of microwave sintering and conventional H2 sintering on the microstructure and properties of W-15Cu alloy using ultrafine W-15Cu composite powder fabricated by spray drying & calcining-continuous reduction technology were investigated.In comparison to the conventional H2 sintering processing,microwave sintering to W-15Cu can be achieved at lower sintering temperature and shorter sintering time.Furthermore,higher performances in microwave sintered compacts were obtained,but high microwave sintering temperature or long microwave sintering time could result in coarser microstructures.     

Effects of activated sintering process on properties and microstructure of W-15Cu alloy

The effects of activated sintering technology of H2 atmosphere sintering on the microstructure and properties of W-15Cu alloy using ultrafine W-15Cu composite powder fabricated by spray drying calcining-continuous reduction technology were investigated.The experimental results showed that W-15Cu alloy,consolidated by activated sintering technology of H2 atmosphere sintering for 1 h at 1300 ℃,with 98.5 % relative density,transverse rupture strength 1218 MPa,Vickers hardness HV0.5 378,average grain size about 1.2 μm and thermal conductivity 192 W/m·K,was obtained.In comparison to the normal sintering process,activated sintering process to W-15Cu alloy could be achieved at lower sintering temperature.Furthermore,better properties in activated sintered compacts were obtained,and activated sintering process resulted in finer microstructure and excellent properties.     

抑制剂对W-15Cu合金性能与结构影响研究

以喷雾干燥-共还原法制备的W-15Cu超细复合粉末为原料,采用氢气活化烧结制备了W-15Cu高比重合金,研究了晶粒生长抑制剂Y2O3对合金性能与结构的影响。利用扫描电镜、维氏硬度仪、密度测试仪、金相显微镜等,观察烧结体显微结构,测试其硬度、密度与断裂强度。结果表明,在最佳烧结温度下,添加质量分数0.3%Y2O3的W-15Cu合金抗弯强度达到最大值1 128.6 MPa,添加质量分数0.5%Y2O3的W-15Cu维氏硬度达到最大值2.78 GPa,优于未添加抑制剂的W-15Cu合金。Y2O3可以细化W晶粒。     

Microstructure and properties of W-15Cu alloys prepared by mechanical alloying and spark plasma sintering process

W-15Cu composite powders prepared by mechanical alloying （MA） of raw powders were consolidated by spark plasma sintering （SPS） process at temperature ranged 1 230-1 300 ℃ for 10 min and under a pressure of 30 MPa. By using high energy milling, particles containing very fine tungsten grains embedded in copper, called composite particles, could be produced. The W grains were homogeneously dispersed in copper phase, which was very important to obtain W-Cu alloy with high mechanical properties, fine and homogeneous microstructure. The microstructure and properties of W-15Cu alloys prepared by SPS processes at different temperature were researched. The results show that W-15Cu alloys consolidated by SPS can reach 99.6 % relative density, and transverse rupture strength （TRS） is 1 400.9 MPa, Rockwell C hardness （HRC） is 45.2, the thermal conductivity is 196 W/m-K at room temperature, the average grain size is less than 2 μm, and W-15Cu alloy with excellent properties, homogeneous and fine microstructure is obtained.     

Consolidation and microstructures of microwave sintered W-25Cu alloys with Fe addition

W-25Cu alloys were microwave sintered in a 2.45 GHz multimode applicator. The densification, microstructure and their dependence on sintering mode and Fe addition were investigated in detail. Owing to the volumetric heating intrinsic in microwave processing, a microstructure with larger W grain size in center regions was observed as against larger grain size in edge regions for conventional sintering. Microwave sintering demonstrates its intrinsic advantages such as rapid heating rate, densification enhancement and microstructural homogeneity; but it undesirably promotes W grain growth. Under microwave sintering, the role of Fe addition on compact consolidation is not so substantial as under conventional sintering. Moreover Fe degrades the microstructural quality, generating worse uniformity and coarser W grains.     

Fabrication and plasma arc thermal shock resistance of HfB2-based ultra high temperature ceramics

Two hafnium diboride based ceramic matrix composites containing 20% (volume fraction) SiC particle and with or without AlN as sintering additives were fabricated by hot-pressed sintering. The mechanical properties and microstructures of these two composites were tested and the thermal shock resistances were evaluated by plasma arc heater. The results indicate that the composite with AlN as sintering additive has a denser and finer microstructure than composite without sintering additive, and the mechanical properties, thermal shock resistance of the composite with AlN as sintering additive are also higher than those of the composite without AlN. Microstructure analysis on the cross-section of two composites after thermal shock tests indicates that a compact oxidation scale contains HfO₂ and Al₂O₃ liquid phase is found on the surface of composite with AlN, which could fill the voids and cracks of surface and improve the thermal shock resistance of composite.     

VC/Cr3C2对微波烧结超细WC-10Co性能的影响

利用微波烧结技术，研究了添加VC／CBQ晶粒生长抑制剂对WC-10Co超细硬质合金微观结构及性能的影响。结果表明，添加总量质量分数为0．6％的抑制剂的合金的综合性能最好，过量的抑制剂反而会降低合金性能；并且微波烧结合金不论是否有晶粒长大抑制剂，均能得到均匀的细晶结构。     

常压烧结与微波烧结ZTA陶瓷性能

选择Al2 O3 -ZrO2 系统 ,采用微波烧结及常压烧结两种工艺 ,分别对ZTA陶瓷的力学性能和摩擦性能进行了测试比较 ,简单分析了影响ZTA陶瓷摩擦性能的主要因素 ,微波烧结使陶瓷的烧结温度降低 ,致密度提高 ,摩擦因数增大 ,磨损量减小     

铜颗粒分散铌酸钾钠压电复合材料的制备与性能

在工业氮气(N2)气氛条件下制备了锂掺杂铌酸钾钠/铜(NKLN/Cu)压电复合材料,研究了铜含量对复合材料的相结构、密度、电学性能及力学性能的影响。结果表明:复合材料由NKLN陶瓷相和Cu金属颗粒两相组成,不同Cu含量复合材料的相对密度均达到95%以上。复合材料的介电常数随Cu含量的增加而急剧增加,压电常数和机电耦合系数随Cu含量的增加而减小,当Cu的体积分数达到20%时,NKLN/Cu复合材料的介电性能和压电性能均难以测量。NKLN/Cu复合材料的显微硬度随Cu含量的增加而降低,断裂韧性值随Cu含量的增加而升高,从铌酸钾钠陶瓷的1.01 MPa逐渐增至Cu的体积分数为40%时的2.81 MPa。     

Effects of Microstructure Modification on Properties of AIN/BN Composites

It is very difficult to prepare full-densified aluminum nitride-boron nitride(AIN/BN)composite ceramics with homogeneous microstructure and high thermal conductivity.Spark plasma sintering(SPS)was used to fully densify the AIN/BN composites in this work.Microstructure,mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated.The results show that the microstructure of composites is fine and homogenous,and the AIN/BN composites exhibit high mechanical properties.To promote the growth of AIN grains and modify the distribution of grain boundary in AIN/BN composites,a heat treating methodology was introduced through gas pressure sintering(GPS).This processing was significantly beneficial to enhancing the thermal conductivity of the specimen.The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.     

Effects of Mierostructure Modification on Properties of MN/BN Composites

It is very difficult to prepare full-densified aluminum nitride-boron nitride(AIN/BN) composite ceramics with homogeneous microstructure and high thermal conductivity.Spark plasma sintering (SPS)was used to fully densify the AlN/BN composites in this work.Microstructure,mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated.The results show that the microstructure of composites is fine and homogenous,and the AIN/BN composites exhibit high mechanical properties.To promote the growth of AlN grains and modify the distribution of grain boundary in AIN/BN composites,a heat treating methodology was introduced through gas pressure sintering(GPS).This processing was significantly beneficial to enhancing the thermal conductivity of the specimen.The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.     

烧结温度和成分对Al_2O_3-TiC复合材料力学性能影响

以α-Al2O3粉、TiC粉为原料,采用热压烧结工艺制备了Al2O3-TiC复合材料,系统研究了烧结温度以及成分对Al2O3-TiC复合材料的组织结构和力学性能的影响规律.结果表明:α-Al2O3与TiC间没有发生化学反应,两相间具有很好的化学相容性.TiC的引入有利于提高Al2O3-TiC复合材料的力学性能.1 600℃热压烧结的Al2O3-20%TiC复合材料具有最佳的力学性能,其抗弯强度和断裂韧性分别达到509.45 MPa和5.27 MPa·m1/2,复合材料的断裂方式主要是沿晶断裂,同时伴有穿晶断裂.     

Microstructure and strength modification of relaxor ferroelectric ceramics through microwave sintering for multilayer capacitors

Relaxor ferroelectric ceramics with the composition of xPb( Mg_(1/3) Nb_(2/3)O_3-yPb (Zn_(1/3)Nb_(2/3)O_3-zPbTiO_3 was fast sintered in a 2.45 GHz microwave system. Microwave-sintered samples illustrate more rapid densification and much smaller grain size microstructure than eonventional sintered samples. Also the microwave processing significantly increases the dielectric strength and flexural strength of the relaxor so that its strength becomes comparable with modified BaTiO_3, and could obtain comparable dielectric properties in comparison with conventional sintering process. Microwave processing has many advantages for sintering of relaxor ferroelectrie ceramics used as multilayer capacitors.     

Effects of microstructure modification on properties of AlN/BN composites

It is very difficult to prepare full-densified aluminum nitride-boron nitride （AIN/BN） composite ceramics with homogeneous microstructure and high thermal conductivity. Spark plasma sintering （SPS） was used to fully densify the AIN/BN composites in this work. Microstructure, mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated. The results show that the microstructure of composites is fine and homogenous, and the AIN/BN composites exhibit high mechanical properties. To promote the growth of AIN grains and modify the distribution of grain boundary in AIN/BN composites, a heat treating methodology was introduced through gas pressure sintering （GPS）. This processing was significantly beneficial to enhancing the thermal conductivity of the specimen. The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.     

Stainless steel binder for the development of novel TiC-reinforced steel cermets

Steel reinforced TiC composites are an attractive choice for wear resistance and corrosion resistance applications. TiC- reinforced 17-4PH maraging stainless matrix composites were processed by conventional powder metallurgy （P/M）. TiC-reinforced maraging stainless steel composites with 〉97% of theoretical density were fabricated. The microstructure, mechanical and wear properties of the composites were evaluated. The microstructure of these composites consisted of spherical and semi-spherical TiC particles. A few microcracks appeared in the composites, showing the presence of tensile stress in the composites produced during sintering. Typical properties, namely, hardness and bend strength were reported for the sintered composites. After heat treatment and aging, the increase of hardness was observed. The increase of hardness was attributed to the aging reaction in the 17-4PH stainless steel. The precipitates appeared in the microstructure and were responsible for the increase in hardness. The specific wear behavior of the composites was strongly dependent on the content of TiC particles, the interparticle spacing, and the presence of hard precipitates in the binder phase.     

Microstructure and Properties of W-Cu Alloys Prepared with Mechanically Activated Powder

W-15% Cu (mass fraction) alloys were sintered with mechanically activated powder in order to develop new preparing processes and improve properties of alloys. The microstructures of the activated powder and the sintered alloy were observed. Properties such as density were measured. The results show that through mechanical activation, the particle size of the powder becomes finer to sub-micron or nanometer level, some copper was soluble in tungsten, and high density W-Cu alloys can be obtained by mechanically activated powder for its action to the activation sintering.     

低介Ba(Al0.98Co0.02)2Si2O8-Ba5Si8O21基LTCC微波介质陶瓷的研究

采用传统固相反应法,按摩尔比合成0.7Ba(Al_0.98Co_0.02)₂Si₂O₈?0.3Ba₅Si₈O₂₁(BACS-BS)基陶瓷,分析Li₂O-B₂O₃(1wt%)(L-B)烧结助剂对其烧结特性、相组成和微波介电性能的影响,探讨0.7BACS-0.3BS+1wt%(L-B)陶瓷理论与实验介电常数(ε_r)的差异。结果表明:添加1wt%(L-B)烧结助剂能有效降低0.7BACS-0.3BS基陶瓷的烧结温度(950 ℃),但严重影响其微波介电性能;在950℃烧结的0.7Ba(Al_0.98Co_0.02)₂Si₂O₈-0.3Ba₅Si₈O₂₁+1wt%(Li₂O-B₂O₃)陶瓷具有较好的微波介电性能,其ε_r=7.56, Q×f=13 976 GHz, τ_f=?6.32 ppm/℃;0.7BACS-0.3BS+1wt%(L-B)复合陶瓷与Ag电极有很好的化学相容性,这为其在LTCC技术的应用奠定了良好的基础。     

Microstructure and thermal properties of SiCp/Cu composites with Mo coating on SiC particles

SiCp/Cu composites with a compact microstructure were successfully fabricated by vacuum hot-pressing method. In order to suppress the detrimental interfacial reactions and ameliorate the interfacial bonding between copper and silicon carbide, molybdenum coating was deposited on the surface of silicon carbide by magnetron sputtering method and crystallized heat-treatment. The effects of the interfacial design on the thermo-physical properties of Si Cp/Cu composites were studied in detail. Thermal conductivity and expansion test results showed that silicon carbide particles coated with uniform and compact molybdenum coating have improved the comprehensive thermal properties of the Si Cp/Cu composites. Furthermore, the adhesion of the interface between silicon carbide and copper was significantly strengthened after molybdenum coating. Si Cp/Cu composites with a maximum thermal conductivity of 274.056 W/(m·K) and a coefficient of thermal expansion of 9 ppm/K were successfully prepared when the volume of silicon carbide was about 50%, and these Si Cp/Cu composites have potential applications for the electronic packageing of the high integration electronic devices.     

Physico-chemical properties and microstructure of hydroxyapatite-316L stainless steel biomaterials

Sintering shrinkage, compressive strength, bending strength, metallurgical morphology, microstructure and chemical composition diffusion of hydroxyapatite-316L stainless steel(HA-316L SS) composites were investiga-ted. The results show that the sintering shrinkage of HA-316L SS composites decreases from 27.38O/6o to 8.87% for cylinder sample or from 27.18% to 8.62% for cuboid sample with decreasing the volume ratio of HA to 316L SS,which leads to higher sintering activity of HA compared with that of 316L SS. The compressive strength of HA-316L SS composites changes just like parabolic curve (245.3→126.3→202.8 MPa) with reducing the volume ratio of HA to 316L SS. Bending strength increases from 86.3MPa to 124. 2 MPa with increasing the content of 316L SS. Furthermore, comprehensive mechanical properties of 1.0：3.0 (volume ratio of HA to 316L SS) composite are optimal with compressive strength and bending strength equal to 202. 8 MPa and 124. 2 MPa, respectively. The microstructure and metallurgical structure vary regularly with the volume ratio of HA to 316L SS. Some chemical reaction takes place at the interface of the composites during sintering.     

纳米颗粒弥散强化铜基复合材料的显微组织与性能

采用粉末冶金的方法,以Al2O3,SiO2,SiC和MgO等纳米颗粒为增强相,制备出4种不同颗粒的纳米复合材料,研究了各增强相对复合材料显微组织与性能的影响.结果表明:在相同的质量分数(ω)和制备工艺下,不同弥散相颗粒的弥散强化铜合金显微组织不同,铜基体上大体均匀地分布着细小的弥散相颗粒,但部分区域仍存在偏聚现象.4种复合材料的电导率相近,抗拉强度方面Cu/Al2O3与Cu/SiO2的性能要略好于Cu/SiC与Cu/MgO.