基于MoSi2／316L不锈钢连接的烧结工艺及其梯度过渡层优化

采用放电等离子烧结(SPS)技术,以MoSi2/316L不锈钢梯度材料作为过渡层连接MoSi2 与316L不锈钢,优化了具体的连接工艺和梯度过渡层.结果表明优化得到的连接工艺为:以100 ℃·min-1速度升温至1000 ℃,保温10 min,再以6 ℃·min-1速度冷却至600 ℃后随炉冷却.其中升温时的烧结压力为50 MPa,降温时为40 MPa;优化得到的梯度过渡层结构为:梯度层层数n=7,梯度层厚度d=0.8,梯度层各层MoSi2的体积分数分别为:40%,50%,60%,70%,80%,90%,95%;利用优化后的梯度过渡层结构和连接工艺,经SPS烧结可实现MoSi2与316L不锈钢的连接.梯度层组织致密、均匀,界面结合良好,未出现明显的裂纹或其他缺陷.     

铜基石墨烯复合材料的制备及性能研究

为了解决铜的硬度等力学性能差的问题,设计了用泡沫铜为基底和催化剂,通过化学气相沉积(CVD)法制备分布均匀的Cu/3DGNs复合材料.经电火花放电等离子烧结(SPS)制备成高强高导的铜基石墨烯复合材料,在保留铜基体优异的导电、导热等性能的同时提高其力学性能.结果表明,采用硝酸清洗,800℃退火30min,反应气体(H_2/Ar/0.95%C_2H_4-Ar混合气体)流量比为80∶4 000∶5sccm,生长温度为1 000℃、生长时间为10s时,制备的石墨烯表面平整、层数较少、覆盖率高、几乎没有缺陷,石墨烯的形貌最佳;采用600℃的烧结温度、25kN的烧结压力、100℃/min的升温速率梯度烧结,制备出的铜基石墨烯复合材料最为致密,性能最优.     

W-Re高比重合金的SPS烧结

采用放电等离子烧结(SPS)设备制备了W-Re高比重合金,烧结温度为1800℃,烧结压力为40MPa,保温时间为5min。对SPS烧结的W-Re合金试样进行了密度、硬度等性能测试。采用金相显微镜观察试样的金相组织、晶粒大小。结果表明:采用SPS烧结,可以在较低的温度下实现W-Re合金的致密化,并能有效控制晶粒长大,提高材料的硬度。     

SPS法制备Al2O3/Cu复合材料研究

将纳米级A12O3以体积分数为1％的配比与微米级Cu粉混合均匀后,采用放电等离子烧结(SPS)法,分别在750、800和850℃进行烧结制备复合材料;将同样的混合粉末采用冷压烧结制备复合材料作为对比.分别测试材料的密度、硬度、导电率,并进行SEM扫描电镜分析.结果表明:在所选择试验参数下,烧结温度为800℃ SPS烧结试样具有最高的相对密度,达到99.17％,硬度与导电率也最高;与冷压烧结制备的材料相比,SPS法制备的试样硬度和导电率更高;SPS烧结试样晶粒均匀细小,并出现了孪晶.     

烧结工艺对MoSi2/316L接头组织形貌的影响

以MoSi2/316L梯度材料作为过渡层,采用放电等离子烧结技术实现了MoSi2与316L不锈钢的连接,着重研究了烧结温度、烧结压力及保温时间对MoSi2/316L接头组织形貌的影响.结果表明:烧结温度与压力的升高有利于改善接头组织与形貌,保温时间对连接性能影响不大;在50MPa、1 050℃×10min工艺条件下,可得到致密的MoSi2/316L连接接头,该接头无宏观缺陷及层间开裂,界面结合紧密,组织形貌良好.     

放电等离子烧结制备超细晶钨钛合金

采用放电等离子烧结法制备了Ti原子数分数在15％～30％的钨钛合金,研究了不同Ti含量钨钛合金的相组成、微观结构和超细晶形成机制.结果表明:采用放电等离子烧结技术可在1100℃、保温5 min的条件下制备出含β1(Ti,W)和β2(Ti,W)两相的钨钛合金,在Ti元素偏聚和快速烧结的共同作用下,厘米级块体样品的晶粒尺寸...     

放电等离子烧结技术

综述了放电等离子烧结(SPS)技术在国内外的发展概况,深入探讨了SPS的烧结机理.介绍了SPS技术在制备纳米材料、梯度功能材料和高致密度、细晶粒陶瓷等方面的研究和应用.展望了SPS技术的发展前景.     

碳的形态对烧结Fe-Cu-C系材料性能的影响

为了研究碳对粉末冶金铁基材料性能的影响,以Fe粉、Cu粉和C粉为原料,在950℃、50MPa条件下放电等离子烧结制备Fe-Cu-C材料.采用扫描电镜、力学万能实验机和洛氏硬度仪对烧结体的微观组织、抗拉强度、抗弯强度和硬度进行了表征,研究了碳的含量、粒度及形态对材料性能的影响,并对比研究了放电等离子烧结和热压试样的性能....     

放电等离子烧结材料的最新进展

放电等离子烧结 (SPS)是一种快速烧结新工艺。将瞬间、断续、高能脉冲电流通入装有粉末的模具上 ,在粉末颗粒间即可产生等离子放电 ,导致粉末的净化、活化、均化等效应。本文简要介绍SPS的基本概念、工艺原理和特征 ,较详细叙述利用SPS工艺在研究开发功能梯度材料、电磁材料、精细陶瓷、硬质合金和生物材料等方面的最新进展     

放电等离子烧结法制备以升华性材料为造孔剂的人体植入骨替代多孔镁块体材料

以萘为造孔剂, 采用放电等离子烧结技术(spark plasma sintering, SPS)制备多孔镁块体材料。结果表明, 采用放电等离子烧结技术在470℃时可以制备出结构与尺寸可控性好、开孔率与孔隙率(44.25%)较高、粉体颗粒无明显长大的多孔金属镁块体材料。升华性造孔剂可对孔隙体积进行有效调节, 实现多孔镁材料体内小孔与大孔的合理搭配, 进一步改善多孔镁材料孔隙之间的连通性。将升华性造孔剂与放电等离子烧结技术相结合后, 对于开孔性与颗粒连接性要求较高的多孔金属材料制备具有技术优势, 并对解决传统造孔剂法制备生物多孔金属材料所面临的二次污染问题具有很好的借鉴意义。     

Design and fabrication of W-Mo-Ti-TiAl-Al system functionally graded material

To obtain a kind of functionally graded material (FGM) with a density gradient, the W-Mo-Ti-TiAl-Al system graded material was designed, and the powder metallurgy method was chosen for its fabrication. The sintering of W, W-Mo, and Mo-Ti alloys at low temperature was studied, and then the approximately wholly dense W-Mo-Ti-TiAl system FGM was achieved by one-step sintering at 1473 K for 1 hour under a pressure of 30 MPa. It was found that through sintering at 1473 K, mainly the mechanical mixtures of W and Mo were formed in W-Mo alloys. In Mo-Ti alloys, the newly designed Fe-Al sintering aids not only have an important effect on the densification of the alloys, but also contribute to the formation of the (Mo, Ti) solid solution. However, the solid-solution reaction that occurred in Mo-Ti alloys was still insufficient. During the sintering of Ti + TiAl, the chemical reaction of Ti + TiAl → AlTi₂ was induced within the sintered body. The W-Mo-Ti-TiAl-Al system FGM was finally fabricated by joining of the TiAl side of the sintered W-Mo-Ti-TiAl system FGM to metal Al with an Al-based brazing filler metal, and its density changed quasi-continuously within the large range from 17.15 to 2.70 g/cm³.     

第一壁材料SiC/C功能梯度材料的制备

以硼、碳为助烧剂 ,选择适当的成分组成 ,用热压法制备出块体SiC/C功能梯度材料。该材料无微观裂纹 ,梯度趋势明显 ,抗热冲击性能良好 ,辐照实验结果显示辐照前后材料组织结构无明显变化。     

超重力下燃烧合成TiC(Ti,W)C1-x基细晶复合陶瓷研究

采用超重力下自挤压辅助燃烧合成技术,以快速凝固方式制备出TiC-(Ti,W)C1-x基细晶复合陶瓷.XRD、FESEM与EDS结果表明,TiC基复合陶瓷基体主要由球状的TiC细晶构成,同时在TiC-(Ti,W)C1-x基体问还分布着少量的TiB2片晶、(Cr,W,Ti)3B2及Al2O5残余夹杂物.由于超重力的引入,促...     

Ti(C,N)基金属陶瓷功能梯度材料的制备

介绍了Ti(C,N)基金属陶瓷功能梯度材料的主要制备技术，即真空烧结后氮化处理和直接在N2气氛中烧结；对两种技术所制得的金属陶瓷的成分分布，表层及过渡层的组织和性能特点进行了总结；并结合热力学计算结果，论述了其显微组织的形成机理；最后对今后的研究方向提出了建议。     

表层富立方相超细晶梯度硬质合金微观结构

通过富氮气氛烧结WC?10TiC?0.5VC?0.5Cr2C3?12Co和WC?12Co硬质合金,研究梯度结构和均匀结构硬质合金的微观结构及力学性能.利用扫描电子显微镜观察合金断面的微观形貌,使用X射线衍射仪和能谱仪分析合金物相组成,并对合金表面和芯部的硬度与断裂韧性进行测试.结果表明:与均匀结构的WC?12Co硬质合...     

微波诱发自蔓延高温反应合成Ti_2SnC材料

以Ti,Sn和C粉末为原料,通过微波诱发SHS反应制备Ti_2SnC材料。研究结果表明,采用活性炭为C源,会发生自蔓延高温反应,反应后得到Ti_2SnC为主相的材料,同时含有一定量的TiO2,Sn,TiC和Ti6Sn5相。样品的表面由大量钛锡氧化物的柱状和针状晶粒构成。柱状晶粒长约12~18μm,宽度约为1~4μm。针状晶粒长约1~4μm,宽度约为0.2μm。试样的内部主要为颗粒状钛锡化合物与碳化钛晶粒,以及片状Ti_2SnC晶粒。采用碳黑为C源,更易于促进Ti_2SnC材料的合成。     

表层富立方相WC-TiC-Co功能梯度硬质合金

采用粉末冶金技术制备WC-15%TiC-6%Co硬质合金(质量分数), 通过控制氮气压力、固相烧结温度和烧结时间对合金进行渗氮烧结, 得到表层富立方相WC-TiC-Co功能梯度硬质合金。利用扫描电子显微镜、X射线衍射仪和能谱仪研究硬质合金梯度区域的微观组织、物相组成及元素分布。结果表明: 制备的WC-TiC-Co硬质合金梯度层厚度大于20 μm, 并且表层富含Ti元素和N元素, 其组成形式为Ti(C_0.7, N_0.3)。     

WC-TiC-TaC无金属粘结相硬质合金的热压致密化与晶粒生长行为

采用Cr、V掺杂超细WC与TaTiC2型单一相成分WC-36.5TiC-24.5TaC复式碳化物粉末为原料,通过1 700℃、20 MPa热压工艺,制备WC-3.65TiC-2.45TaC-0.47Cr3C2-0.28VC无金属粘结相硬质合金。采用X射线衍射分析技术研究烧结过程中的物相转变,采用扫描电镜与能谱仪对合金微观组织结构特征进行观察与分析。结果表明,在高温、高压固相烧结过程中,发生了W原子向复式碳化物中的大量固溶、TaTiC2型固溶体向TiWC2型固溶体的物相转变以及固溶体中Ta、Ti原子向WC中的反向固溶。合金固相烧结致密化主要机制为W原子与Ta、Ti原子之间的非平衡体扩散机制以及高温、高压下物质的粘性/塑性流动机制。W原子在固溶体型复式碳化物粘结相中的各向异性溶解-析出会显著削弱晶粒生长抑制剂的功能,导致板状WC晶粒的形成。     

Titanium-titanium boride (Ti-TiB) functionally graded materials through reaction sintering: Synthesis,microstructure, and properties

The study demonstrates an effective method to synthesize titanium-titanium boride (Ti-TiB) functionally graded material (FGM) tiles by exploiting the simultaneous TiB whisker formation in situ and the densification occurring during the reaction sintering process. The macrostructure of the graded material was designed to have a beta-titanium (β-Ti) layer on one side with the composite layers of Ti-TiB mixture having increasing volume fraction of the TiB through the thickness. The approach used an optimized tri-modal powder mixture consisting of α-Ti powder, a master alloy of the β-stabilizing-element powders (Fe-Mo), and TiB₂. The structure and properties of both of these FGMs were systematically characterized by X-ray diffraction, electron microscopy, and microhardness measurements. Interestingly, it has been found that two different kinds of TiB whisker morphologies were observed in the FGMs. The Ti-rich layers were found to have large and pristine TiB whiskers uniformly distributed in the Ti matrix. On the other hand, the TiB-rich layer was found to have a network of interconnected and relatively smaller TiB whiskers appearing as clusters. The layers of intermediate TiB volume fractions were found to consist of both the morphologies of TiB. The effectiveness of the X-ray direct comparison method for the determination of volume fractions of phases in the FGM layers was also demonstrated. The Vickers microhardness level was found to increase dramatically from 420 kgf/mm² in the β-Ti layer to 1600 kgf/mm² in the TiB-rich layer. The elastic residual stresses retained in the graded layers after fabrication were determined based on an elastic multilayer model. The nature of microstructure, the hardness variation, and the distribution of residual stresses in these novel FGMs are discussed.     

Correlation of microstructure with hardness and wear resistance in (TiC,SiC)/stainless steel surface composites fabricated by high-energy electron-beam irradiation

Stainless-steel-based surface composites reinforced with TiC and SiC carbides were fabricated by high-energy electron beam irradiation. Four types of powder/flux mixtures, i.e., TiC, (Ti + C), SiC, and (Ti + SiC) powders with 40 wt. pct of CaF₂ flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with an electron beam. TiC agglomerates and pores were found in the surface composite layer fabricated with TiC powders because of insufficient melting of TiC powders. In the composite layer fabricated with Ti and C powders having lower melting points than TiC powders, a number of primary TiC carbides were precipitated while very few TiC agglomerates or pores were formed. This indicated that more effective TiC precipitation was obtained from the melting of Ti and C powders than of TiC powders. A large amount of precipitates such as TiC and Cr₇C₃ improved the hardness, high-temperature hardness, and wear resistance of the surface composite layer two to three times greater than that of the stainless steel substrate. In particular, the surface composite fabricated with SiC powders had the highest volume fraction of Cr₇C₃ distributed along solidification cell boundaries, and thus showed the best hardness, high-temperature hardness, and wear resistance.