APPLICATION OF HOT-PRESS SINTERING TECHNIQUE TO EXPLOSIVE CHARGE LINER OF PETROLEUM PERFORATION BULLET

介绍了一种制备石油射孔弹的药形罩的新方法，采用粉末冶金技术，热压烧结工艺制备石油射孔弹的药形罩，并对药形罩的烧结工艺进行了研究。实验结果表明，采用该工艺制备的石油射孔弹药形罩可以满足要求。

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

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.

Preparation of ZrB_2 Ceramics by Self-propagating High-temperature Synthesis and Hot Pressing Sintering

ZrB2 ceramics were prepared by self-propagating high-temperature synthesis（SHS） and were sintered by hot pressing（HP）.The effects of the granularities and doses of raw materials in Zr-B2O3-Mgon SHS process and product were investigated.XRD and combustion temperature curves prove that the ideal SHS reactants of Zr-B2O3-Mg are 50μm Zr powder,75μm B2O3 powder and 400μm Mg powder with 45% excessive.The particle sizes of SHS product,acid-leached product,sintered product are 2-5μm,0.5-2μm,2-10μm respectively.Chemical analysis indicates that the acid-leached product consists of ZrB2（94.59%）,ZrO2（3.87%）,and H3BO3（1.54%）,The sintered product has a relative density of 95.4%.

Effect of La_2O_3 on microstructure and high-temperature wear property of hot-press sintering FeAl intermetallic compound

FeAl intermetallic compound with different contents of rare earth oxide La2O3 addition was prepared by hot pressing the mechanically alloyed powders.Effect of La2O3 on microstructure and high-temperature wear property of the sintered FeAl samples was investigated in this paper.The results showed that 1 wt.% La2O3 addition could refine the microstructure and increase the density of the FeAl intermetallic compound,and correspondingly improved the high-temperature wear resistance.SEM and EDS analyses of the wo...

Hot-press sintering of MA Fe-based nanocrystalline/amorphous soft magnetic powder

Microstructures and magnetic properties of Fe84Nb7B9,Fe80Ti8B 12 and Fe32Ni36（Nb/V）7Si8B17 powders and their bulk alloys prepared by mechanical alloying（MA） method and hot-press sintering were studied. The results show that: 1) After MA for 20 h,nanocrystalline bcc singl e phase supersaturated solid solution forms in Fe84-Nb7B9 and Fe8 0Ti8B12 alloys,amorphous structure forms in Fe32Ni36Nb7 Si8B17 alloy,duplex microstructure composed of nanocrystalline γ- （FeNi） supersaturated solid solution and trace content of Fe2B phase forms in Fe32Ni36-V7Si8B17 alloy. 2) The decomposition process of supersaturated solid solution phases in Fe84Nb7B9 and Fe80Ti8B 12 alloys happens at 710780 ℃,crystallization reaction in Fe （32）Ni36Nb7Si8B17 alloy happens at 530 ℃（the temperature of peak value） and residual amorphous crystallized further happens at 760 ℃ （the temperature of peak value）,phase decomposition process of supersaturated solid solution at 780 ℃ （the temperature of peak value） and crystallization reaction at 431 ℃ （the temperature of peak value） happens in Fe32Ni36V7S i8B17 alloy. 3) under 900 ℃,30 MPa,（0.5 h） hot-press sintering conditions,bulk alloys with high relative density（94.7%95.8%） can be ob tained. Except that the grain size of Fe84Nb7B9 bulk alloy is large,s uperfine grains （grain size 50200 nm） are obtained in other alloys. Exc ept that single phase microstructure is obtained in Fe80Ti8B12 bul k alloy,multi-phase microstructures are obtained in other alloys. 4) The magne tic properties of Fe80Ti8B12bulk alloy（Bs=1.74 T,Hc= 4.35 kA/m） are significantly superior to those of other bulk alloys,which is r elated to the different phases of nanocrystalline or amorphous powder formed dur ing hot-press sintering process and grain size.

Study on Squeeze Casting Metal-zirconium Composite Die Material by Hot Press Sintering

ZrO_(2)-5CrMnMo composite samples were prepared by hot press sintering.When NiCoCrAlY powders were used as the bonding layer and the different mixtures of NiCoCrAlY alloy and 3YSZ (3mol% yttria stabilized zirconia) ceramic powders were used as the transition layers,the connection between zirconia ceramic and 5CrMnMo steel were strengthened.Three composite samples with different structures were fabricated by heat spraying and hot press sintering.Shear and thermal shock cycle tests were conducted to characterize connection strength and thermal shock resistance of these samples.The shear strength reached 95.69 MPa,and the heating shock cycles achieved to the maximum value of 27.7 times.Microstructures and connection interfaces were analyzed by scanning electron microscopy.The hardness and wearing resistance of 3YSZ coat and 5CrMnMo substrate were compared,and the heat insulation property of composite samples were also discussed.It is shown that these composite materials fabricated in this research are benefited to be used as squeeze casting dies.

Preparation and Characterization of Hot-Pressed and Sintered BiPbSrCaCuO Superconductor

Powder compacts of the system Bi2–xPbxSr2Ca2Cu3Oy with 0 ≤ x ≤ 0.5 molar ratio using both techniques;isothermal hot pressing and the solid state reaction (sintering). The XRD of the hot pressed powder compacts of the nominal compositions Bi2–xPbxSr2Ca2Cu3Oy showed 2212 and 2223 phases. The resistivity temperature variations belonging to the composition Bi1.8Pb0.2Sr2Ca2Cu3Oy showed metal-superconducting transition at Tons = 143 K for the annealed sample for 24 h. The annealed nominal composition Bi1.5Pb0.5Sr2Ca2Cu3Oy for 18 h showed metal to superconducting transition at 80 K.

Fine-grained NdFeB magnets prepared by low temperature pre-sintering and subsequent hot pressing

Fine-grained Nd10.79Pr2.8Al0.4B7.72Fe78.29 magnets were prepared by low temperature pre-sintering and subsequent hot pressing. The grain size of the magnets is just about 1–3 μm because the low sintering temperature results in no grain growth. The orientation degree, microstructure, and magnetic properties were studied. Some grains＇ easy axes deviate from the orientation direction, possibly due to grain rotation during the hot pressing. By subsequent annealing, the magnetic properties were significantly enhanced. Especially, the squareness of the demagnetization curve was improved greatly.The enhancement of coercivity by annealing can be explained by an improvement of both grain boundaries and magnetic isolation, which decouples the exchange interaction between neighboring grains.

Reactive Hot-press Sintering of Al-B_4C Composites at Relative Low Temperature

A new process of reactive hot-press sintering with boron carbide(B4C) and aluminum powders was proposed to overcome difficulties in the sintering of dense B4C ceramic materials.The B4C powder with different content of pure metallic aluminum particle were milled,hot-pressed and sintered at 1600 ℃ for 1 hour.The mechanism of sintering at relative low temperature was analyzed.The phase constitution of the composites was determined.Effects of Al content on the hardness and fracture toughness of the composites were discussed.The results show that thermite reaction procedure in B2O3+Al was the mechanism of sintering at relative low temperature,B4C,Al2O3 and metallic aluminum are the major constituents of the composites.The microhardness of the composites decreases with the increasing of Al content,but the fracture toughness increase obviously.The composite with 5wt% Al content has the best microhardness and fracture toughness in all the composites.

Synthesis of high-purity Ti_2AlN ceramic by hot pressing

High-purity Ti2AlN ceramic was prepared at 1300 ℃ by hot pressing(HP)of Ti/Al/TiN powders in stoichiometric proportion.The sintered product was characterized using X-ray diffraction(XRD)and MDI Jade 5.0 software(Materials Data Inc,Liverpool,CA).Scanning electron microscopy(SEM)and electron probe micro-analysis(EPMA)coupled with energy-dispersive spectroscopy(EDS)were utilized to investigate the morphology characteristics.The results show that Ti2AlN phase is well-developed with a close and lamellar structure.The grains are plate-like with the size of 3-5 μm,thickness of 8-10 μm and elongated dimension.The density of Ti2AlN is measured to be 4.22 g/cm3,which reaches 97.9% of its theory value.The distribution of Ti2AlN grains is homogeneous.

Repetitious-Hot-Pressing Technique in Hot-Pressing Process

A new pressing method was proposed for hot-pressing process. Experimental results indicated that the porosity in Al2O3/TiC/ Ni/Mo (hereafter called AI2O3/TiC composite) composite compacts decreases by 6% after adopting this new technique, compared to traditional hot-pressing technique under the same sintering temperature. The flexural strength and Vicker hardness increase from 883 MPa to 980 MPa and from 16 GPa to 21.1 GPa, respectively. A theoretical model was given to analyze the densification mechanism of the composite in the process of repetitious-hot-pressing.

Influence of sintering time on microstructure and properties of hot oscillatory pressing sintered W–Cu refractory alloys

W–Cu refractory alloys are widely used in aerospace,aviation,electronics,power,and other fi elds.However,because of its large melting point diff erence between alloy elements,the conventional powder metallurgy method required a long time of high temperature sintering is very likely to cause low density and abnormal grain size growth.Therefore,90W-10Cu refractory alloys were successfully prepared by hot oscillatory pressing(HOP)under diff erent sintering time in this work.Then the infl uence of sintering time on the microstructure,grain size,density,Vickers hardness,room-tensile property,and electrical conductivity of the W–Cu refractory alloy was systematically invested.The results showed that during the short sintering time(30–90 min),the density,Vickers hardness,tensile strength,and electrical conductivity of the W–Cu refractory alloy increased signifi cantly to 98.7%,163.29 HV 30,507.3 MPa,and 14.2%International Annealed Copper Standard with the sintering time increasing,respectively,while its grain size showed no obvious change.When the sintering time further increased to 120 min,the density was basically consistent with the sintering time of 90 min.Nevertheless,the prolonged high temperature sintering resulted in the grain growth of the samples,which caused the deterioration of the Vickers hardness,room-tensile strength,and conductivity properties of the W–Cu refractory alloy.At the same sintering time,the density,Vickers hardness,and electrical conductivity of the HOP sintered W–Cu refractory alloy were signifi cantly higher than those of the HP sintered sample.It was indicated that high density,fi ne-grain,and excellent properties W–Cu refractory alloys could be prepared by hot oscillatory pressing under appropriate sintering time.

纳米结构Y_(2)O_(3)-Sc_(2)O_(3)-ZrO_(2)固溶体透明陶瓷的热压烧结和性能研究

笔者通过溶胶-凝胶燃烧法成功合成了Y_(2)O_(3)-Sc_(2)O_(3)-ZrO_(2)纳米粉体,研究了ZrO_(2)与热压烧结工艺对Y_(2)O_(3)-Sc_(2)O_(3)-ZrO_(2)固溶体透明陶瓷组织与性能的影响。结果表明,Y_(2)O_(3)-Sc_(2)O_(3)-ZrO_(2)粉体晶粒尺寸随ZrO_(2)掺入量的增加而减小。热压过程中,ZrO_(2)可以有效抑制晶界迁移,提高陶瓷致密度、透过率及强度和韧性。在优化的1300℃,30 min,40 MPa工艺下烧结,Y_(2)O_(3)-Sc_(2)O_(3)-10 mol%ZrO_(2)固溶体透明陶瓷的综合性能最好,其平均晶粒尺寸仅94 nm、致密度98.5%、硬度10.44 GPa,断裂韧性1.42 MPa·m^(1/2)、在3~6μm红外波段最大透过率达到72%。

Formation and Sintering Behavior of Nanocrystalline Fe-Ni Powder by Mechanical Alloying

The solid sintering behavior and mechanical properties of Fe-Ni powders prepared by mechanical alloying of elemental powders and hot pressing sintering in vacuum atmospheres were investigated. It was observed that the microstructure of the powder particles evolves in three stages. The alloy powder with average grain size of 20-30 nm was obtained. The sinter densification depends crucially on the particle rearrangement and the large amount of internal strain introduced during milling. The theoretical density of over 95 % was obtained after hot pressing sintering at 800 ℃ for 30 min with pressure of 50 MPa. No significant grain growth was observed during sintering. And also relatively high hardness was obtained.

Nb元素对铜-金刚石复合材料界面改性的研究

采用粉末冶金法制备铜/金刚石复合材料,研究不同含量活性元素Nb对铜界面改性的影响机制以及对铜/金刚石复合材料的热导率的影响,利用XRD、SEM、EDS和导热系数测定仪分析复合材料的界面和热导率。结果表明,随着Nb含量的添加,能够在烧结过程中形成碳化物界面层,铜和金刚石界面缺陷逐渐减少,界面结合逐渐转好。在1%的含量时,复合材料的热导率达到370.3 W/(m·K),相比纯铜/金刚石复合材料提高1.34倍,但当含量超过1 vol.%,碳化铌中间层变厚,由于碳化铌自身热导率较低,导致复合材料的热导率降低。

Carbon-fiber-reinforced silicon carbide composites prepared by precursor pyrolysis-hot pressing

The Cf/SiC composites were prepared by precursor conversion-hot pressing sintering with AIN and Y2Os as additives. The effects of sintering temperature and additives on the microstructures and properties of the composites were investigated. The composite sintered at as low as 1 75O℃ already showed higher density and better mechanical properties, which was mainly attributed to the liquid-phase-sintering and the formation of the AIN-SiC solid solution. With increasing the sintering temperature to 1 800 ℃, the flexural strength and fracture toughness of the composite were substantially improved up to 691. 6 MPa and 2O. 7 MPa’ m1/2 respectively in spite of the slightly elevated density, and the composite exhibited "tough" failure. Despite the improved density, the composite sintered at 1 85O℃ displayed brittle failure, which mainly attributed to the strongly bonded fiber/matrix interface and the degradation of the properties of the fibers.

Cu-Ag-La_(2)O_(3)功能梯度材料的制备及其性能研究

为提高Cu、Ag、La_(2)O_(3)的界面结合强度,通过化学镀工艺在Ag、La_(2)O_(3)粉末表面镀上均匀、完整和致密的Cu粉。采用热压烧结工艺制备出含有不同成分的三层和五层Ag/Cu/La_(2)O_(3)功能梯度材料,研究成分对两种功能梯度材料的显微组织、致密度和润湿性的影响。

基于无压浸渗工艺的铁-铌酸锂功能梯度材料制备

功能梯度材料(FGM)是一种新型的功能复合材料,通过控制其厚度方向上组分体积含量、化学构成,使材料的宏观特性呈现连续梯度变化,可解决两种不同材料之间的界面突变问题。本文提出一种结合粉末叠层、无压浸渗与真空热压烧结的方法,制备了组分分布连续变化的铁-铌酸锂功能梯度材料。该方法通过分层控制材料体积分布,利用高温金属自重以及黏结剂蒸发所留空隙,使液态金属沿空隙从上到下浸渗,达到消除层间界面的效果,通过真空热压烧结的方法使其达到致密化,最终得到材料体积分布可控的连续功能梯度材料。实验结果表明:经过烧结温度900℃、保温时间120 min的无压浸渗和烧结温度800℃、保温时间120 min并加压35 MPa的真空热压烧结后,所制备的铁-铌酸锂功能梯度材料体积分数沿厚度方向呈线性连续分布。

Grain size refinement of additive manufactured Ce-TZP ceramics by coupled two-step pre-sintering and HIP

Ceria-stabilized tetragonal zirconia polycrystal(Ce-TZP)has exceptional fracture toughness and flaw tolerance due to facile t‒m phase transformation toughening.However,its wider-range applications are limited by its relatively low strength due to its large grain size and low transformation stress,which results in yield-like failure.Here,we combined additive manufacturing(AM),pressureless two-step sintering,and hot isostatic pressing(HIP),and addressed the challenging grain size refinement problem in Ce-TZPs.We successfully produced dense ultrafine-grained Ce-TZP ceramics with an average grain size below 500 nm,a three-point bending strength above 800 MPa,and a single-edge-notch-beam fracture toughness in the range of 11‒12 MPa·m^(1/2).The critical roles of processing design,mixed Ce valences,and under-vs.over-stabilization of tetragonal polymorphs were noted.Our work offers insights and strategies for the future development of stronger and tougher Ce-TZP ceramics that can compete with tetragonal yttria-stabilized zirconia in various applications,including additive manufacturing.

Comparison of a commercial powder and a powder produced from Ti–6Al–4V chips and their effects on compacts sintered by the sinter-HIP method

The present paper is related to the conversion of Ti–6Al–4V chips into powder and investigates the usability of the produced powder in powder metallurgy applications. In this regard, a disc-milling process was applied to Ti–6Al–4V chips and the obtained powder was subsequently compacted. The compacted samples were sintered by the sinter hot isostatic pressing (sinter-HIP) method at 1200°C under high vacuum, their mechanical properties and microstructure were investigated and compared with those of commercial powder compacts subjected to the same preparation processes. The results showed that the produced powder exhibits greater flowability and higher apparent density than the commercial powder. However, the sintered products prepared from the commercial powder exhibited a higher relative density, lower porosity, and, as a result, greater flexural strength compared with the sintered compacts prepared from the produced powder. In addition, transgranular fracture was greater in the sintered products of the commercial powder. The microstructural studies revealed that the sintered products made from both the commercial and the produced powders consisted of α- and β-phase but contained more α-phase. All of the examined properties were found to be substantially affected by the particle size of the powders.