共查询到19条相似文献,搜索用时 156 毫秒
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《稀有金属材料与工程》2016,(8)
针对熔体发泡法制备泡沫镁存在的困难,使用包覆发泡剂及改进工艺成功制得泡孔均匀的泡沫镁试样。利用OM、SEM、EDS及XRD等分析手段对试样进行宏微观结构表征。结果表明:泡沫镁试样宏观孔以典型的闭孔结构为主,但也存在一些连通孔及少量大孔,它们多是宏观裂纹的产生及扩展位置。泡孔内壁存在一些褶皱缺陷,且弥散分布着许多反应产生的MgO和CaO颗粒,压缩变形过程中,这些部位易产生应力集中,促进微裂纹的形成与扩展。孔壁上主要分布着碳化硅颗粒及生成的Mg_2Ca相。测试分析了孔隙率和孔径对泡沫镁压缩力学性能和能量吸收性能的影响,并深入研究其压缩破坏机理。研究发现:随着孔隙率的降低,泡沫镁弹性变形增大,屈服强度升高;随着孔径的增大,泡沫镁屈服强度及平台应力明显减小,表现出显著的孔径效应。随着孔隙率的升高或孔径的增大,泡沫镁的能量吸收性能显著降低。泡沫镁的破坏为解理脆性断裂,这与孔壁组织及镁基体性质有很大的关系。 相似文献
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使用圆盘造粒机制备近球形的NaCl颗粒,并将其用于渗透铸造制备开孔泡沫铝。盐球的平均抗压缩强度为3.9 MPa,在超声波清洗机中可在5 min内完全塌陷。通过控制热压烧结时间为0.5~2 h,热压温度700℃,可制备堆积密度在0.66~0.83 g/cm3的预制体。延长热压烧结时间会使开孔泡沫铝的孔径从0.48 mm增加到1.16 mm,孔隙率从64%增加到82%。压缩实验结果表明,不同孔隙结构下泡沫体的宏观变形特征基本相同,均表现出逐层塌陷的变形特征。此外,泡沫铝的致密化应变值、弹性模量、平台屈服应力和能量吸收能力均随着孔隙率的增加而降低。当孔隙率为64%时,能量吸收能力最大(15.0 MJ·m-3)。 相似文献
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以青铜粉为原料、CaCl_2为造孔剂,采用粉末烧结溶解法制备开孔泡沫青铜。通过改变造孔剂体积分数和粒径成功制备出孔隙率为70%~90%,孔径1~3mm的泡沫青铜试样。研究了孔隙率和造孔剂的关系以及孔隙率、孔径对泡沫试样力学性能的影响,并对其孔结构,相组成和微观形貌进行观察和分析。结果表明:泡沫青铜试样的塑性屈服平台应力随孔隙率增加而减小,当孔隙率为77%~89%时,对应塑性屈服平台应力为12.6~2.6MPa。当应变量为50%时,孔隙率为77%~89%的泡沫青铜单位体积能量吸收值(W)范围为6.21~0.91MJ/m~3。试样的理想吸能效率(I)都接近0.82,说明泡沫青铜可以作为一种理想的吸能材料。 相似文献
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采用固体粉末法在1050°C下对三维网状开孔泡沫Ni表面进行CrFe共沉积,然后经过1200°C高温固相扩散处理对开孔泡沫NiCrFe进行表面合金化。研究不同保温条件下Cr、Fe含量对NiCrFe合金泡沫的准静态压缩性能和能量吸收性能。同时,将开孔NiCrFe合金泡沫的真实力学性能与纯泡沫Ni和假设的NiCrFe合金泡沫模型进行比较。结果表明:不同Cr、Fe含量的开孔NiCrFe合金泡沫骨架显示出相似的硬度,整体上开孔NiCrFe合金泡沫的压缩强度和能量吸收性能随着合金泡沫中Cr、Fe含量的增加而明显增大。开孔NiCrFe合金泡沫的应力—应变行为与纯泡沫Ni相似,表明NiCrFe合金泡沫具有典型韧性金属泡沫的变形特性。同时,单位体积开孔NiCrFe合金泡沫的能量吸收最大值与泡沫Ni相比增加了22倍。经计算得出的NiFeCr合金泡沫的理论屈服强度与实际屈服强度大体一致。 相似文献
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《特种铸造及有色合金》2016,(7)
以孔隙率为71.5%~72.5%的泡沫Al-0.16Sc-0.08Zr合金为研究对象(熔体发泡法),研究了等时时效对泡沫铝压缩力学性能和能量吸收性能的影响。结果表明,泡沫铝合金孔多呈球形,孔径约为0.9mm;由于Zr添加量较少,基体中并未发现初生Al3(Zr,Sc)相析出;试样经200~600℃等时时效,随时效温度升高,其压缩强度先增加后降低,时效至400℃的试样压缩屈服强度和能量吸收能力最强;时效处理会导致胞壁塑性下降,影响试样屈服平台过程,其能量吸收效率得到显著提高,且高效阶段更持久。TEM结果表明,等时时效至400℃的试样胞壁中弥散分布着大量纳米级共格Al_3(Sc,Zr,Ti)相,粒径为2.9~4.8nm。这些纳米相能钉扎晶界,阻碍位错运动,改善其压缩和吸能性能。 相似文献
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胞状AlCu5Mn合金泡沫的压缩性能和能量吸收特性 总被引:2,自引:0,他引:2
用熔体发泡法制备孔隙率为51.5%~90.5%、孔结构均匀的胞状铝合金(AlCu5Mn),研究其孔结构、压缩性能、能量吸收能力、能量吸收效率和吸能性能.结果表明:胞状铝合金孔结构由高孔隙率(88.8%)时的大孔径、多边形孔向低孔隙率(62.5%)时的小孔径、球形孔孔结构过渡,其压缩应力(σ)-应变(ε)曲线具有线性变形阶段、屈服平台阶段和致密化阶段三个部分,由线性变形阶段进入屈服平台阶段所对应的ε_s值介于2%~9%之间;屈服强度σ_s~*随着孔隙率的增大而下降,在孔隙率相同的条件下,胞状铝合金的力学性能优于胞状铝和多孔铝合金,其比刚度高于钢;当应变为定值时,胞状铝合金单位体积和单位质量的压缩吸能能力(C和C_m)都随着孔隙率的升高而降低,但是孔隙率在73.5%~82.1%范围内时,其C_m与ε的关系几乎不随孔隙率的改变而改变;对于孔隙率为51.5%~90.5%的胞状铝合金,它们的吸能效率的峰值都大于80%.胞状铝合金的C-σ和C_m-σ关系可以表征其吸能性能,从而可以根据实际工况选择作为减振吸能材料的胞状铝合金的最佳孔结构. 相似文献
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The infiltration casting fabrication process based on spherical CaCl2 space-holders and the compressive behavior including the mechanical performance and energy absorption capacity of open-cell aluminum foams were investigated.Open-cell aluminum foams with different porosities in the range of 63.1%to 87.3%can be fabricated by adjusting compression ratios of CaCl2 preforms prepared by precision hot-pressing.The compression tests show that a strain-hardening phenomenon always occurs especially for open-cell aluminum foam with low porosity,resulting in the inclining stress-strain curve in the plateau region.The energy absorption capacity of open-cell aluminum foam decreases with increasing porosity when compared at the same strain.However,when compared at a given stress,each foam can absorb the maximal energy among the five foams in a special stress range.Additionally,open-cell aluminum foam possesses the maximum energy absorption efficiency at its optimum operating stress.At this stress condition,the foam can absorb the highest energy compared with other foams at the same stress point.The optimum operating stress and the corresponding maximal energy absorption decrease with increasing the porosity.The optimum operating stress for energy absorption can also be determined similarly when taking into consideration of the lightweight extent of foams. 相似文献
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Nima Movahedi Emanoil Linul Liviu Marsavina 《Journal of Materials Engineering and Performance》2018,27(1):99-108
In this research, the mechanical behavior of closed-cell aluminum (Al)-alloy foams was investigated at different temperatures in the range of 25-450 °C. The main mechanical properties of porous Al-alloy foams are affected by the testing temperature, and they decrease with the increase in the temperature during uniaxial compression. From both the constant/serrated character of stress–strain curves and macro/microstructural morphology of deformed cellular structure, it was found that Al foams present a transition temperature from brittle to ductile behavior around 192 °C. Due to the softening of the cellular structure at higher temperatures, linear correlations of the stress amplitude and that of the absorbed energy with the temperature were proposed. Also, it was observed that the presence of inherent defects like micropores in the foam cell walls induced further local stress concentration which weakens the cellular structure’s strength and crack propagation and cell-wall plastic deformation are the dominant collapse mechanisms. Finally, an energy absorption study was performed and an optimum temperature was proposed. 相似文献
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通过挂浆烧结法制备了两种不同孔隙结构的泡沫钛,利用数码相机和扫描电镜对泡沫钛孔隙结构与形貌观特征进行了观察,通过静态的室温压缩试验,测试了泡沫钛的力学性能与吸能特性。研究发现,应用挂浆烧结法制备的泡沫钛继承了先驱体的结构特征,呈三维立体网状结构,且孔棱是非致密的,存在大量的微孔。泡沫钛是应变速率不敏感的,在应变速率3×10-4s-1~1×10-2s-1范围内,其屈服强度为1.00MPa~2.38MPa,且泡沫钛具有一定的吸能特性,细孔泡沫钛和粗孔泡沫钛的最大吸能量分别为0.78MJ/m3和0.22MJ/m3。 相似文献
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为了丰富泡沫材料制备工艺、推动其快速发展与广泛应用,以CaCO3为发泡剂采用粉末冶金法制备SiCp/2024Al泡沫复合材料。采用SEM和Magiscan-2A图像分析仪研究了CaCO3发泡剂和SiC颗粒的含量对发泡行为的影响,并且通过Gleeble 1500热模拟机分析了SiC颗粒的含量对压缩性能的影响。结果表明:随着发泡剂的增多,孔隙率和孔径先增加后减小。随着增强体含量的增加,孔隙率和孔径都减小。压缩曲线揭示加入增强体可以改善压缩屈服强度和吸能能力。SiCp/2024Al泡沫复合材料显示为脆性泡沫材料。 相似文献
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Vasanth Chakravarthy Shunmugasamy Steven E. Zeltmann Nikhil Gupta Oliver M. Strbik III 《JOM Journal of the Minerals, Metals and Materials Society》2014,66(6):892-897
Silicon carbide hollow spheres are compression tested to understand their energy absorption characteristics. Two types of particles having tap densities of 440 kg/m3 and 790 kg/m3 (referred to as S1 and S2, respectively) were tested in the present study. The process used to fabricate the hollow spheres leads to porosity in the walls, which affects the mechanical properties of the hollow spheres. The porosity in the walls helps in obtaining mechanical bonding between the matrix material and the particle when such particles are used as fillers in composites. The single-particle compression test results show that the S1 and S2 particles had fracture energies of 0.38 × 10?3 J and 3.18 × 10?3 J, respectively. The modulus and fracture energy of the particles were found to increase with increasing diameter. However, the increasing trend shows variations because the wall thickness can vary as an independent parameter. Hollow particle fillers are used in polymer and metal matrices to develop porous composites called syntactic foams. The experimentally measured properties of these particles can be used in theoretical models to design syntactic foams with the desired set of properties for a given application. 相似文献
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SiCp/2024Al composite foams were manufactured by powder metallurgical methods using foaming agent CaCO3 in order to enrich the foam fabrication process and promote its development and extensive application. The effects of CaCO3 and SiC volume fractions on the foaming behaviours were investigated by means of SEM and Magiscan-2A image analysis technique. The influence of SiC content on the compressive behaviour was analyzed using Gleeble 1500 thermal simulation testing machine. The experimental results show that with increasing the foaming agent, the porosity and pore dimension increase first and decrease later. With increasing the reinforcement content, the porosity and pore dimension decrease. The compressive curves reveal that the introduction of SiC particles can improve compressive yield strength and energy absorption capacity. Meanwhile, it is found that SiCp/2024Al composite foams are the brittle foam materials. 相似文献
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以聚氨酯泡沫为前驱体,使用气雾化Ni-20Cr粉末为原料配制水基浆料,采用有机泡沫浸渍工艺制备了具有梯度孔结构的泡沫Ni-20Cr合金滤管。研究了不同烧结温度和装填方式对泡沫金属滤管烧结效果及力学性能的影响,并测试了烧结后泡沫滤管的力学性能和透气性能。结果表明:泡沫素坯经低温预烧+高温烧结的两步烧结工艺后可得到收缩均匀的泡沫合金滤管,孔筋结构均匀、无堵孔且复合界面结合良好。其室温压缩屈服强度大于3 MPa,且随着挂浆量的增加其屈服强度可达4.43 MPa;由于泡沫合金滤管高的孔隙率和大的孔径,且孔结构呈梯度变化,其在气体流量相同的情况下压差明显小于传统粉末冶金烧结多孔管。 相似文献