多孔结构对材料吸波性能的影响

总结了当前多孔材料吸波性能的研究现状，指出多孔结构可改善材料的吸波性能，而孔径、相对密度及厚度是影响多孔材料吸波性能的重要因素，对多孔陶瓷材料而言，适当降低孔径、增加相对密度与厚度有利于提高材料的吸波性能．在此基础上对多孔金属材料泡沫铝的吸波性能进行了初步研究，分析了相对密度与微波频率对材料吸波性能的影响，研究表明，降低多孔金属的相对密度可以显著提高材料的吸波性能；随着微波频率的增加，材料的吸波性能也随之增加．     

轧制方向对粉末轧制多孔钛板力学性能的影响

以氢化脱氢钛粉为原料,采用粉末轧制和真空烧结工艺制备出两种不同厚度的多孔钛板。利用孔径及孔径分布分析、扫描电镜观察、拉伸实验、三点弯曲实验、剪切强度测试等手段,对垂直于轧制方向和平行于轧制方向的板材力学性能进行了研究,并从孔径分布和烧结颈发育方面对其进行了解释。结果表明,1.96 mm厚的多孔钛板比1.32 mm厚多孔钛板的最大孔径小,且其孔径分布相对均匀;对于厚度相同的粉末轧制多孔钛板,垂直于轧制方向的板材平均抗拉强度比平行于轧制方向的增大25%、弯曲强度增大45%;随着轧制多孔钛板厚度的增加,其抗拉强度、弯曲强度、剪切强度等均显著增大,粉末轧制多孔钛板力学性能的方向差异与轧制致密板材的方向差异完全相反。     

粉末粒度对Ti-35A1多孔材料孔结构的影响

粉末粒度是影响Ti-35Al多孔材料孔结构的主要因素之一.本文采用元素粉末反应合成工艺制备Ti-35Al 多孔材料,在其它制备参数一定的条件下,系统研究Ti/Al元素粉末的粒度与Ti-35Al多孔材料的孔隙度、孔径和透气度等孔结构参数之间的定量关系.结果表明:粉末粒度是决定Ti-A1合金多孔材料最大孔径的主要因素,多孔...     

Laws of capillary transport in porous materials prepared from titanium alloy VT6 fibers

A study was made of the kinetics of capillary absorption of ethanol in highly porous (70–75%) materials prepared from discrete fibers of titanium alloy VT6 (specimen dimensions 330×20×(0.4–1.3) mm). The fibers, 3 mm in length and 20–140 μm in diameter, were obtained by rapid solidification from the melt. Capillary transport against the force of gravity up to the equilibrium height of capillary rise was investigated in an atmosphere of saturated ethanol vapor. Experimental data on the rate of absorption were analyzed with reference to the properties of the pore space structure—effective pore size, tortuosity of the pore channels, and free surface area. The laws of capillary transport of ethanol in porous materials composed of titanium alloy VT6 fibers, discrete copper fibers, and grade VTEM-2 titanium powder were compared. It was shown that, with regard to the speed of absorption, the advantage of fiber materials over those made from powder is attributable to the less convoluted pore channels in the former. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 67–74, January–February. 1997.     

Ti-32Mo合金多孔过滤材料的粉末制粒问题

为了用钛、钼粉为原料制取过滤性能优异的Ti-32Mo合金多孔过滤材料,提出了一种新的制粒方法。研究结果表明:采用粉轧生带,经真空低温预烧结、破碎、分级,再经真空高温烧结、研碎、分级的粉末制粒工艺,制得的粗颗粒粉末具有足够高的颗粒强度,在成形过程中仍能保持其颗粒形状。用本制粒工艺所得粗颗粒粉末制取的Ti-32Mo合金烧结过滤片,其性能与海绵钛粉所制烧结过滤片相比,在孔径相同的条件下,空气相对透气系数高,特别是在大孔径的情况下,其值甚至高出一倍以上。本制粒工艺亦可推广到其它用细粉未(如钨、钼、钛、锆等)制取粉末冶金多孔过滤材料的生产中。     

添加Cr合金化FeAl金属间化合物多孔材料的制备及性能

在Fe-25%Al金属间化合物成分基础上,添加铬(Cr)元素进行合金化,通过元素偏扩散-反应合成-烧结的方法制备含Cr的铁铝(FeAl)金属间化合物多孔材料,并采用X射线衍射(XRD)分析反应合成过程中的物相变化,采用孔结构测试仪、排水法、弯曲试验和冲击试验研究Cr含量对FeAl金属间化合物多孔材料孔结构和力学性能的影响,通过静态腐蚀实验研究Cr合金化FeAl多孔材料的耐腐蚀性能。结果表明:Cr含量为20%时,制得的FeAl多孔材料物相仍为单一FeAl相;其中,Cr含量为5%~10%时,FeAl多孔材料的强度和韧性值较高;随Cr含量增加,FeAl多孔材料的孔径和孔隙度均增大,材料的氧化和硫化速率显著降低。     

Permeability of porous materials from refractory compounds

Summary A study was made of porous materials from spheroidized powders of refractory compounds. A relationship is established linking permeability with porosity and the particle size of the powder from which the materials were prepared. An empirical formula is proposed for determining the dependence of the coefficient of permeability on powder particle size and component porosity under linear filtration conditions. The integral and differential pore radius distribution curves obtained show that such materials are relatively homoporous and exhibit little scatter in pore radius size.Translated from Poroshkovaya Metallurgiya, No. 1(49), pp. 27–30, January, 1967.     

Ni-Cr-Co-W-Mo-Al-Ti合金制备多孔材料的组织与性能研究

用粉末烧结法制备了孔结构为球形中空孔和线型中空孔的镍基多孔高温合金材料.对试样进行显微组织观察和力学性能测试.结果表明:制备的多孔高温合金材料的孔隙分布均匀,孔径大小一致.通过高温烧结,多孔合金骨架处的金属颗粒之间形成了烧结颈,发生了烧结结合.生成孔的孔隙度随造孔剂(尿素)的添加量增加而增加,当造孔剂的质量分数为40%时,可得到孔隙度为81.62%的球形多孔材料.多孔材料具有优良的能量吸收性能,其压缩性能随孔隙度和孔径的增加而下降.     

人工髋关节用复合多孔钛股骨头制备方法的研究

本研究采用等离子旋转电极制取的Tc4钛合金球形粉末,涂覆在致密芯杆上,制成柄部表面多孔层厚度约2mm的复合多孔钛股头。本文着重研究了原始粉末粒度、烧结制度、基体表面粗糙度对复合多孔层的孔径、孔隙度以及多孔层与基体间结合强度的影响,同时还测定了复合多孔钛股头的机械性能。研究结果表明,材料的最大孔径主要取决于原始粉末粒度,并随粉末粒度的增大而线性增加。影响结合强度的主要因素是烧结制度、原始粉末粒度和基体表面粗糙度。其结合强度随烧结温度的提高、保温时间的延长、原始粉末粒度的下降和基体表面粗糙度的增加而增加。孔隙度仅取决于粉末的堆积状态。所获得的复合多孔钛股头的机械性能为σ_b=830~880 MPa,σ_0.2=810~840 MPa,σ=9.5~12.0%,ψ=26.0~33.0%。     

Fe-Al系金属间化合物多孔材料的制备及孔结构表征

以Fe、Al元素粉末为原料,采用分段无压反应合成工艺制备Fe-Al系金属间化合物多孔材料,并对其孔结构进行表征.通过改变Fe-Al元素的配比,研究Al含量对Fe-Al金属间化合物多孔材料透气度和最大孔径以及孔隙度的影响.结果表明,Al含量对Fe-Al金属间化合物多孔材料孔隙度的影响显著.在Al含量(质量分数)20%～45%的范围内,Fe-Al金属间化合物多孔材料的孔隙度与Al含量之间遵循严格的直线增加规律;Al含量对Fe-Al金属间化合物多孔材料最大孔径和透气度的影响与对孔隙度的影响相似.本实验条件下Fe-Al系金属间化合物多孔材料中透气度(k),开孔隙度(θ)和最大孔径(dm)之间的定量关系式为:K=0.2538dm2θ.     

Effect of the method of production of porous powder metallurgy materials on their capillary properties (review)

The unique features of liquid infiltration in capillary porous powder metallurgy materials (CPPM) are discussed. The effect of the production method on the maximum height and rate of capillary rise of a liquid in CPPM is clarified. It is shown that in materials with a uniform pore structure, and the same average pore size, the maximum value of H_max is attained when the form factor of the initial powder particles is a minimum. The highest values of liquid infiltration rate at closely similar heights of capillary rise (within 5–7%) were obtained in CPPM with a variable pore distribution prepared from mixtures of powders with dtiferent particle sizes (pseudo fluidization method), or in CPPM with a biporous structure prepared by the sintering of a previously oxidized powder, by compacting metal powder with a pore forming agent, as well as by the cathodic deposition of a porous copper structure from electrolytic solution.Scientific Research Institute for Powder Metallurgy, Minsk. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 30–39, May-June, 1996. Original article submitted July 14, 1994.     

A properties comparison for porous materials from various metallic fibers and powders

Conclusions Powder fiber materials have a more finely porous structure than is the case with drawn fiber materials under conditions of equal porosity and a single fiber diameter, however they are characterized by lower permeability and mechanical strength indices; the specific surface of powder fiber materials is twice that of drawn fibers, ali other conditions being equal.Powder fiber materials exhibit a more uniform structure and better permeability than powder materials given the same porosity; they also differ in terms of the greater strength at the same permeability.In effectiveness terms, powder fiber materials that have the same o B value are typified by the K value and the overall K/D_max parameter, and occupy an intermediate position between porous drawn fiber materials and powders.Translated from Poroshkovaya Metallurgiya, No. 1(349), pp. 45–48, January, 1992.     

烧结过滤材料使用性能与粉末粒度及烧结工艺的关系

本文从理论推导和实验数据探讨了松装烧结过滤材料使用性能(过滤精度、过滤效率)与原料粉末粒度、粒度组成及烧结工艺参数(烧结温度)之间的数学关系。运用多项式回归方法和微机分析处理,建立了相应的数学模型。从而为合理选择原料粉末粒度和最佳烧结工艺参数以制取符合预定使用性能要求的过滤材料提供了理论和实验依据。在一定条件下,数学模型对制取粉末冶金多孔材料具有指导意义。     

氢一次还原钨粉烧结多孔构件的工艺研究

研究了氢一次还原、平均粒度为6.5—7.5μm的钨粉的烧结特性。得出多孔钨构件的相对密度随烧结温度和时间、粉末粒度、压制件密度而变化的规律。提出了生产相对密度为78—81%、开孔率>95%的多孔钨的生产工艺参数,即:压制件相对密度为60—65%,烧结温度为2100—2250℃、时间为4—8小时。     

添加升华性造孔剂的放电等离子法制备多孔铝块体材料

为解决高孔隙率多孔金属材料制备过程中的污染问题,以升华性萘颗粒为造孔剂,采用放电等离子脉冲烧结法(SPS)进行多孔铝块体材料的制备。结果表明,升华性造孔剂可在实现多孔铝材料高孔隙率的同时,有效提高其洁净度。采用该方法在350℃时可以制备出结构与尺寸可控性好、开孔效果好、孔隙率(63.33%)较高、粉体颗粒无明显长大的多孔金属铝块体材料。升华性造孔剂可对孔隙体积进行有效调节,实现多孔铝材料体内小孔与大孔的合理搭配,进一步改善多孔铝材料孔隙之间的连通性,该方法与SPS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。     

Electrical conductivity and contact phenomena in porous metallic materials

The change in electrical resistance of copper fiber and powder compacts upon heating from room to the sintering temperature was studied. It was found that different regimes of heating in vacuum did not affect the temperature dependence of electrical resistance. A relationship between electrical conductivity and the relative size of interparticle contacts was derived for a model fiber body. This was in good agreement with data on the tensile strength of real fiber materials.     

Manufacturing porous materials from metalorganic mixtures: Report 2

The morphology of the surface and fracture of highly porous materials obtained during the thermal destruction of metalorganic mixtures (MOM) was investigated. The size and shape of pore channels in the finished product were shown to be determined through the fractional composition and the particle shape in MOMs. The effect of the porosity on the permeability and strength of sintered materials was considered. The permeability was demonstrated to depend not only on the value, but also on the shape of pore channels. Combining the techniques of powder metallurgy with chemical-metallurgical processes allows us to obtain materials with a porosity of 70–80% and a strength of no less than 5–25 MPa. If the pore size was from 10 to 100 μm, the permeability of materials was (in 10⁻¹² m²) 1–3 for Mo, 0.5–6 for Mo-Ni, and 2–6 for Ti-Mo.     

Synthesis and characterization of porous Fe–25 wt.% Al alloy with controllable pore structure

Porous Fe–25 wt.% Al alloy is synthesized by reactive synthesis with Fe and Al powders as the raw materials. Various processing parameters such as the final sintering temperature, pressure during cold pressing, and powder size are investigated to control the pore structure of the alloy. It has been shown that the optimal final sintering temperature is around 950–1050°C. When the pressure is higher than 110 MPa, the variation of the pore structure is mainly caused by the change of the pore nature in the as-pressed compact. In addition, the pore structure of porous Fe–25 wt.% Al alloys depends on the size of the raw powders and the weight fraction of different-sized raw powders.     

钛粉粒度对轧制烧结多孔钛板力学性能的影响

对不同粒度钛粉的流动性、松装密度和振实密度进行分析, 经轧制和烧结制备出满足湿法冶金需求的多孔钛板, 研究了钛粉粒度对轧制烧结多孔钛板力学性能的影响。结果表明: 轧制烧结多孔钛板的最大孔径和孔隙度随钛粉粒度的减小而减小, 钛板密度、剪切强度、抗弯强度、抗拉强度及伸长率均随钛粉粒度的减小有所增加; 当钛粉粒度范围为89~104 μm时, 粉末轧制烧结多孔钛板的综合力学性能较高。     

Investigation of the trends in air flow through porous materials made of dendritic powders

Conclusions We performed investigations for determining the hydraulic resistance coefficients of porous cermet materials made of stainless steel powder with dendritic particles, screened into fractions of –0.38, +0.28 mm and –0.16+0.10 mm. The specimens had a thickness of 2–8 mm and a porosity of 30–55%, while the temperatures of the air forced through were in the range of up to 200°C.A qualitative dependence of the viscous hydraulic resistance coefficient on the size of the initial particles was established; the thickness of the specimens did not affect the viscous coefficient.The inertial hydraulic resistance coefficient is virtually independent of the size of the initial particles; however, this coefficient is materially affected by changes in the thickness of specimens.The air flow through the investigated materials is adequately described by Eq. (8).It was found that the determining dimension depends on the size of the initial powder particles and the specimen's thickness; no appreciable effect of porosity on the determining dimension was observed. However, this observation presently applies only to the materials investigated. Further experimental investigations are necessary before this conclusion can be extended to other materialsTranslated from Poroshkovaya Metallurgiya, No. 12, pp. 52–57, December, 1967.