烧结压力对低液相Fe基预合金钻头胎体性能的影响

在烧结温度为950℃、保温时间为5 min及不同烧结压力条件下开展热压烧结试验，对比研究烧结压力对3种低液相Fe基预合金钻头胎体和1种传统Fe基钻头胎体性能的影响，具体包括胎体压入硬度、抗弯强度、致密度和金刚石包镶强度等力学性能，以及金刚石的热损伤情况和钻头胎体的微观组织结构与形貌特征等。结果表明：随着烧结压力增大，低液相空白胎体的压入硬度、抗弯强度和致密度逐渐增大，而传统Fe基空白胎体的压入硬度和抗弯强度呈现先增大后减小的趋势，其致密度为增大趋势；对于含金刚石的胎体，低液相与传统Fe基胎体抗弯强度均随烧结压力增大而增大，当烧结压力为20 MPa时，继续增大压力，低液相含金刚石胎体的抗弯强度趋于稳定，而传统Fe基含金刚石胎体的抗弯强度略有下降。同时，随着烧结压力的增大，低液相胎体的均一性明显增强，但金刚石的热损伤加剧。综合胎体的力学性能与断口形貌特征，优选的烧结压力为20 MPa，此时的低液相Fe基预合金胎体硬度、抗弯强度可满足孕镶金刚石钻头需要。     

基于Bi2O3-B2O3体系的陶瓷结合剂金刚石砂轮制备及其对单晶硅的磨削性能

针对陶瓷结合剂烧结温度高的问题，提出一种基于Bi₂O₃-B₂O₃的新型低温陶瓷结合剂。分析添加纳米SiC和纳米ZrO₂对结合剂物相组成、流动性和力学性能的影响，并探索添加核桃壳粉造孔剂对金刚石砂轮微观形貌的影响；制备基于Bi₂O₃-B₂O₃体系的陶瓷结合剂金刚石杯形砂轮，测试其对单晶硅晶圆片的磨削性能。结果表明：添加纳米SiC会导致陶瓷结合剂中出现一定量的Bi单质，破坏结合剂的[BiO₄]玻璃网络；添加纳米SiC及纳米ZrO₂后，结合剂的流动性降低；随烧结温度上升，结合剂的流动性、抗弯强度和硬度有增大的趋势，在560℃烧结时结合剂的抗弯强度和硬度达到最大。随着造孔剂含量的增大，砂轮中大气孔的数量显著增多、尺寸显著增大。在砂轮线速度为12.56 m/s，工件转速为5.23 m/s，进给速度为0.1μm/s条件下，使用以M10/20金刚石(粒度号为80...     

金属结合剂金刚石砂轮中铝基结合剂性能优化研究

以AlSi₂₀为主元，选择强化铝的常用合金元素Cu、Zn、Mg、Mn等4因素（分别用A、B、C、D表示），每个因素各取3个水平，制定了L₉（34）正交试验方案。采用热压烧结制备铝基结合剂胎体。通过阿基米德排水法、硬度测试、三点弯曲强度测试、扫描电镜观察断口形貌等方法，研究合金元素对铝基结合剂性能的影响。实验结果表明:添加的合金元素降低AlSi₂₀的烧结温度，促进烧结致密化；合金元素对硬度的影响大小顺序为Mn>Zn>Cu>Mg，对抗弯强度的影响大小顺序为Cu>Mn>Zn>Mg；组合A₁B₂C₂D₂、A₁B₃C₃D₃有高的硬度和抗弯强度，胎体对金刚石包镶紧密；结合剂断裂方式为脆性断裂，可以提高金刚石砂轮的自锐性。      

热压工艺参数对WC-Cu基胎体力学性能的影响

在深部钻探中,WC-Cu基金刚石钻头胎体被广泛使用。为了提高钻头使用性能,在同一胎体配方下,采用正交试验方案对热压参数进行设计,并烧制试样进行抗弯强度和显微硬度测试。通过方差和极差分析不同烧结温度(A)、烧结压力(B)、保温时间(C)、冷却方式(D)对金刚石钻头胎体力学性能的影响。试验结果表明:对纯胎体和含金刚石胎体抗弯强度影响的顺序为A>D>B>C;对胎体维氏硬度影响的顺序是A>C>B>D。本次正交试验中的最优理论烧结参数为A₃B₃C₁D₄,即烧结温度为960 ℃、烧结压力为16 MPa、保温时间为3 min、冷却方式为400 ℃保温炉冷。此时,与理论参数最接近的工艺试验结果为:纯胎体抗弯强度为983.33 MPa、硬度为437.40 HV,金刚石胎体试样抗弯强度为525.00 MPa。      

不同Y2O3含量的YSZ块体材料在模拟海洋环境下的腐蚀行为研究

针对钇稳定氧化锆(YSZ)材料在海洋环境中易腐蚀的问题，使用放电等离子烧结技术分别制备了5%和12%(质量分数) Y₂O₃稳定的YSZ块体材料，并对块体材料在高低温交替的水蒸气环境中进行腐蚀实验，模拟其作为热障涂层面层材料在海洋环境下使用时的腐蚀情况。分析了YSZ在低温水蒸气老化和高温烧结的交替腐蚀过程中，力学性能的变化以及裂纹的形成和扩展行为。结果表明：对于5%Y₂O₃含量的5YSZ在模拟海洋环境下抗弯强度损失严重，14 d的腐蚀实验使得抗弯强度下降了91.4%。然而对于高Y₂O₃含量的12YSZ材料，其在相同环境下腐蚀相同时间，抗弯强度未有明显变化。Y₂O₃含量高的YSZ具有更强的稳定性，更适合在海洋环境使用。     

第二代FeCuCo预合金粉末的烧结与力学性能研究

采用国产真空热压烧结机制备了第二代FeCuCo预合金粉末的胎体试样,着重研究了不同烧结温度对胎体的断口形貌、相对密度、硬度和抗弯强度的影响。结果表明:在选定的不同热压烧结温度下,胎体的断口均为沿晶断裂和穿晶断裂的混合型断口,胎体的晶粒尺寸比较均匀;随着烧结温度的升高,胎体内的晶粒逐渐长大,但没有发生异常长大现象,胎体的相对密度先略有升高然后恒定不变,硬度一直呈下降趋势,抗弯强度先升高后下降;在30 MPa保压6 min的条件下,第二代FeCuCo预合金粉末的最佳烧结温度为850℃,此时胎体的相对密度为97.5%,硬度为105.5 HRB,抗弯强度为1 839.14MPa。     

ZrO2(Y2O3)含量对Mo-12Si-8.5B-ZrO2(Y2O3)复合材料高温氧化性能的影响

为了研究ZrO₂(Y₂O₃)含量对Mo-12Si-8.5B-ZrO₂(Y₂O₃)复合材料高温氧化性能的影响，利用机械合金化与放电等离子烧结制备了ZrO₂(Y₂O₃)含量为0～10 mass%的Mo-12Si-8.5B-ZrO₂(Y₂O₃)复合材料，研究了其在800、1000和1200℃下的高温氧化行为。结果表明：复合材料在800℃时均发生显著氧化，质量损失持续增加；随着ZrO₂(Y₂O₃)含量的增加，氧化质量损失速度降低，复合材料的抗氧化能力提升；低ZrO₂(Y₂O₃)含量(0～2.5 mass%)的复合材料在1000和1200℃下具备优异的抗氧化性；高ZrO₂(Y_...     

Y2O3/Sn-58Bi复合钎料制备及其性能分析

文中通过粉末冶金法制备了Y₂O₃/Sn-58Bi复合钎料.结果表明,添加少量Y₂O₃,对复合钎料熔点影响较小;随着Y₂O₃质量分数提高,复合钎料的密度和显微维氏硬度先升高后降低;复合钎料的润湿角表现出相反的趋势,随着Y₂O₃质量分数提高,复合钎料的润湿角先降低后升高.通过测试Sn-58Bi钎料和0.1%（质量分数）Y₂O₃/Sn-58Bi复合钎料拉伸试样的力学性能发现,添加质量分数为0.1%的Y₂O₃对复合钎料强度稍有提高,但能明显提高复合钎料的延展性,从而解决传统Sn-58Bi钎料较脆的难题.通过观察钎料拉伸断口发现,添加Y₂O₃能够细化复合钎料微观组织,使裂纹沿着断裂方向扩展时受到阻碍,抑制了钎料脆性断裂的趋势.     

B2O3含量对SiO2–B2O3–Al2O3–Na2O系陶瓷结合剂结构与性能的影响

制备不同B₂O₃含量的SiO₂–B₂O₃–Al₂O₃–Na₂O系玻璃试样和陶瓷结合剂试样,利用电子多功能实验机、扫描电镜、显微硬度仪、平面流淌法、热膨胀系数测试仪等分别测试不同玻璃试样的密度和显微硬度,陶瓷结合剂试样的抗折强度、微观形貌和热膨胀系数等,并用X射线衍射仪、傅里叶变换红外光谱仪对陶瓷结合剂的结构和成分变化进行分析。结果表明:将B₂O₃引入陶瓷结合剂中可有效降低其烧结温度,提高其热稳定性并调节其热膨胀系数等。在陶瓷结合剂中加入摩尔分数为15%的B₂O₃时,其样条抗折强度最高为78.11 MPa,密度和硬度最高分别为2.45 g/cm3和856 MPa,且该陶瓷结合剂的热膨胀系数与金刚石最匹配。X射线衍射分析结果表明陶瓷结合剂是典型的玻璃相结构,且对磨料有良好的包覆效果。      

粉末粒度对SPS固相烧结La0.6Eu0.4B6阴极材料的影响

采用高能球磨法制备出La_0.6Eu_0.4B₆纳米粉体,将球磨后的纳米粉进行放电等离子（SPS）烧结,制备出了高致密的La_0.6Eu_0.4B₆多晶块体材料。系统研究了烧结温度、烧结压力对样品致密度和力学性能的影响。结果表明,该方法与传统热压烧结方法相比有效降低了烧结温度,制备出的样品密度、维氏硬度和抗弯强度分别达到4.71g/cm3、23.37GPa和295.14MPa,这些值均高于传统热压烧结方法。热电子发射结果表明,当阴极温度为1873K时,最大发射电流密度为33.74A/cm2。实验过程中还发现,在相同烧结工艺下,球磨纳米粉与粗粉相比,维氏硬度、抗弯强度和热电子发射电流密度分别提高了28%、58%和32%。因此,在固相烧结过程中,粉末粒度的减小,更有助于烧结性能的提高。     

烧结压力对热压掺钙铬酸镧陶瓷组织和性能的影响

采用热压法在不同烧结压力下制备了高密度掺钙铬酸镧基陶瓷(La_0.8Ca_0.2Cr_0.98O₃),研究了烧结压力对La_0.8Ca_0.2Cr_0.98O₃陶瓷微观结构、力学性能和导电性能的影响。结果表明,当烧结压力大于58 MPa时,在烧结陶瓷中检测到第二相CaCr₂O₄的存在。CaCr₂O₄在烧结陶瓷中有两种完全不同的形态。烧结压力的提高不仅可以提高铬酸镧基陶瓷的密度,同时能显著抑制晶粒长大。随着烧结压力的增加,弯曲强度和硬度逐渐增加,但是断裂韧度和电导率发生下降。     

Effect of starting powders size on the Al2O3–TiC composites

Al₂O₃–TiC composites with a content of 30 wt% TiC with various size of starting powders were manufactured by hot pressing. The Vickers hardness, bending strength and fracture toughness were studied. The experiment results show that the starting powder size has a significant effect on the properties of the Al₂O₃–TiC composites. The maximum bending strength of the submicron Al₂O₃ with the fine TiC powders addition is 712 MPa, while the maximum fracture toughness of the same Al₂O₃ matrix with the large TiC powders addition is 6.5 MPa m^1/2.     

Processing, microstructure, and properties of laser remelted Al2O3/Y3Al5O12（YAG） eutectic in situ composite

Laser remelting and rapid solidification were performed in preparing the high-performance Al2O3/Y3Al5O12（YAG） eutectic in situ composite. The microstructure characteristic and solidification behavior were studied using scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS）, X-ray diffractometry（XRD） and simultaneous thermal analysis（STA）. The hardness and fracture toughness were obtained using an indentation technique. The results show that the laser remelted Al2O3/YAG composite has a homogeneous eutectic microstructure without microcrack and pore. The component phases of Al2O3 and YAG are three-dimensionally and continuously reticular connected, and finely coupled without grain boundaries, colonies and amorphous phases between interfaces. The eutectic interspacing is greatly refined with increasing the scanning rate and average is only l μm. The synthetically thermal analysis indicates that the eutectic temperature of Al2O3-YAG is 1 824 ℃, well matching the phase diagram of Al2O3-Y2O3 system. The maximum hardness reaches 19.5 GPa and the room fracture toughness is 3.6 MPa.m^1/2.     

Properties of ZrO2–Al2O3 composite as a function of isothermal holding time

Zirconia and alumina based ceramics present interesting properties for their application as implants, such as biocompatibility, good fracture resistance, as well as high fracture toughness and hardness. In this work the influence of sintering time on the properties of a ZrO₂–Al₂O₃ composite material, containing 20 wt% of Al₂O₃, has been investigated. The ceramic composites were obtained by sintering, in air, at 1600 °C for sintering times between 0 and 1440 min. Sintered samples were characterized by microstructure and crystalline phases, as well as by mechanical properties. The grain growth exponents, n, for the ZrO₂ and Al₂O₃ were 2.8 and 4.1, respectively, indicating that different mechanisms are responsible for grain growth of each phase. After sintering at 1600 °C, the material exhibited a dependency of hardness as function of sintering time, with hardness values between 1500 HV (120 min) and 1310 HV (1440 min) and a fracture toughness of 8 MPa m^1/2, which makes it suitable for bioapplications, such as dental implants.     

14Cr-ODS钢的热时效行为

为探究氧化物弥散强化(Oxide dispersion strengthened, ODS)钢的热稳定性,采用机械合金化和热等静压烧结的方法制备成分为Fe-14Cr-2W-0.3Ti-0.2V-0.07Ta-0.3Y₂O₃ (wt%)的14Cr-ODS钢,在700 ℃分别对其进1000、2000和3000 h时效处理,表征了ODS钢组织及第二相在热时效过程中的变化规律,同时分析了ODS钢的维氏硬度值。结果表明:M₂₃C₆相在时效过程中逐渐溶解,促进了TiC相和Y₂Ti₂O₇相的析出。烧结态ODS钢中球状的Y₂Ti₂O₇相在长时间的时效过程中逐渐转变为立方状,且Y₂Ti₂O₇相的尺寸在时效过程中未发生变化。当时效时间延长至2000 h和3000 h时,ODS钢的基体组织及第二相保持稳定,硬度结果也与该现象相对应。     

Thermal cycle behavior of plasma sprayed La2O3, Y2O3 stabilized ZrO2 coatings

The effects of La₂O₃ addition on thermal conductivity, phase stability and thermal cycle life of Y₂O₃ stabilized ZrO₂ plasma sprayed coatings were investigated. Although low thermal conductivity as well as high resistance to sintering was achieved by La₂O₃ addition, it tended to also result in lower phase stability and thermal cycle life of the coatings. Optimization of the composition and structure of the coatings improved these properties, and the optimized coatings showed prolonged thermal cycle life.     

In situ technique for synthesizing multiple ceramic particulates reinforced titanium matrix composites (TiB + TiC + Y2O3)/Ti

In situ synthesized titanium matrix composites reinforced with multiple ceramic particulates including TiB, TiC and Y₂O₃ were fabricated by non-consumable arc-melting technique utilizing the chemical reaction among Ti, B₂O₃, B₄C and Y. The thermodynamic feasibility of the in situ reactions has been considered. X-ray diffraction (XRD) was used to identify the phases in the composites. Microstructures of the composites were observed by means of optical microscope (OM), scanning electron microscope (SEM) and electron probe. It is concluded that multiple reinforcements are synthesized and they show different shapes: TiB grows in needle shape; TiC grows in near-equiaxed and rod-like shapes; Y₂O₃ grows in near-equiaxed shapes when the content of Y is 0.6 wt.% and grows in dendritic shapes when the content of Y increases to 1.8 wt.%. Reinforcements TiB, TiC and Y₂O₃ are distributed uniformly in the titanium matrix.