多孔CoCrNi中熵合金的制备和吸能特性分析

本文采用粉末烧结-溶解法成功制备了孔隙率为63%~78%,孔径1.3~2.2mm的多孔CoCrNi中熵合金,借助SEM和XRD对试样的孔形貌和物相组成进行分析,并对试样进行轴向准静态压缩实验研究。结果表明：多孔CoCrNi中熵合金的弹性模量和屈服平台应力均随孔隙率、孔径的增大而减小;相对孔隙率而言,孔径对力学性能的影响程度较低;不同孔隙率的多孔CoCrNi中熵合金其致密应变下单位体积的能量吸收值为34.8~14.3MJ/m₃^,约为泡沫铝的3.8倍,且5种孔隙率的理想吸能效率(I)都接近0.8,说明该多孔CoCrNi中熵合金有潜力成为一种理想的吸能材料。     

多孔蒙乃尔合金的制备及其结构特性

为了制备蒙乃尔合金多孔材料,本文以蒙乃尔粉为原料,以K2CO3为造孔剂,采用烧结-溶解法制备了不同孔隙率的蒙乃尔合金多孔试样。研究了造孔剂体积分数、压坯压力和烧结温度对试样孔隙率、孔径和透气度的影响。实验结果表明,当造孔剂的体积分数在20%~ 40%之间时,制备的样品孔隙率为31%~46%。当压坯压力在200~400MPa范围时,随压力的增大试样的孔隙率、孔径和透气度均减小;当烧结温度在850~1000℃范围时,随烧结温度升高,孔径和透气度先增大后缓慢降低,在950℃达到峰值。当造孔剂体积分数为30%,压制压力为200MPa,烧结温度950℃时,所制备的蒙乃尔多孔材料孔隙率为37%,最大孔径为21.5μm,透气度为76.77 m3/(h?kPa?m2)。     

尿素作为造孔剂制备泡沫钛的结构和力学性能

采用针状尿素作为造孔剂,在造孔剂含量介于60%~80%的情况下进行了泡沫钛的制备。通过造孔剂技术成功地制备出孔隙率介于50.2%~71.4%的泡沫钛。扫描电镜结果表明,孔的连通程度随着造孔剂含量的增加而增加,当造孔剂含量超过70%时形成开孔泡沫钛。力学性能测试结果表明,力学性能随着孔隙率的增加而减小,试样的屈服强度、抗压强度和杨氏模量分别介于34.4~146.8 MPa、40.6~193.2 MPa和0.5~3.3 GPa。孔隙率为50.2%和71.4%的泡沫钛的杨氏模量分别匹配于皮质骨和松质骨的模量,理论上可作为潜在的骨替代材料。     

医用多孔Ti-10Mo合金的制备及力学性能

以元素粉末为原料添加造孔剂碳酸氢铵,采用粉末冶金模压烧结技术制备了多孔Ti-10Mo合金,探讨了烧结工艺与造孔剂含量对合金组织、孔隙特征和力学性能的影响规律。结果表明,在1300℃烧结可制备出具有典型魏氏体组织、孔隙分布均匀的多孔Ti-10Mo合金材料;随着造孔剂含量增加,合金孔隙率增加,孔径变大孔壁变薄,当造孔剂含量达到50%,孔隙结构互相贯通,孔径尺寸大幅增加;添加50%~60%造孔剂,制备Ti-10Mo合金孔隙率为62.8%~66.9%,平均孔径尺寸为485.6~545.9μm,其弹性模量为2.9~1.3 GPa,抗压屈服强度为129.2~56.1 MPa。     

中孔隙率通孔多孔铝合金的压缩性能研究

在采用复模铸造工艺制备孔径3.5~4.0 mm、孔隙率65.8%~87.3%的通孔多孔铝合金基础上,通过单轴压缩试验,研究通孔多孔铝合金的压缩性能和吸能能力。通孔多孔铝合金单轴压缩应力应变曲线,呈现线弹性变形、塑性平台段和压缩紧实阶段3个阶段。通孔泡沫铝合金的压缩屈服强度、吸能能力随孔隙率增大而减小,通孔多孔铝合金的压缩屈服强度与Gibson-Ashby的模型拟合结果吻合。     

塑性中孔隙率通孔多孔铝的压缩性能研究

在采用熔模铸造工艺制备孔径d=2.5~3.5mm和d=3.8~4.3mm,孔隙率P=56.8%~86.6%的通孔多孔铝基础上,通过单轴压缩试验,研究通孔多孔铝的压缩性能和吸能能力。通孔多孔铝单轴压缩应力应变曲线,呈现线弹性变形、塑性平台段、压缩紧实阶段3个阶段;通孔泡沫铝的压缩屈服强度、吸能能力随着孔隙率增大而减小,采用Gibson-Ashby的模型拟合通孔多孔铝的压缩屈服强度。     

泡沫镁制备及抗压缩性能（英文）

作为一种新型结构和功能材料,泡沫金属具有比实体金属更优异的性能。本研究利用粉末冶金造孔剂法成功制备了孔隙率为38.9%~57.5%泡沫镁。随着孔隙率从38.9%增加到57.5%时,其弹性模量由8.5 GPa下降到3.3 GPa,初始屈服应力从24.90 MPa下降到9.40 MPa。泡沫镁具有较低的初始屈服应力和较长的应力平台,因此,它可以作为优异的缓冲吸能材料。     

造孔剂大小对泡沫钛孔隙结构的影响

采用3种颗粒大小的尿素作为造孔剂,在造孔剂含量相等的条件下进行了泡沫钛的制备,考察了造孔剂大小对泡沫钛结构和力学性能的影响,讨论了造孔剂大小对烧结泡沫孔隙率的影响。添加粒度更小的造孔剂颗粒,有利于提高生压坯的致密度。小颗粒造孔剂制备的泡沫钛的孔径更小,孔棱的结构和厚度分别更加致密和均匀。改变造孔剂的颗粒大小,泡沫钛应力-应变曲线的弹性部分变化不大,坍塌平台有明显的变化。结果表明,泡沫钛的相对密度和杨氏模量随着造孔剂粒径的减小而微弱的增大,而抗压强度则明显的增大。分析表明,泡沫钛的宏观大孔在烧结过程的体积收缩量随着造孔剂粒径的减小而减小。     

通孔多孔铝的压缩性能研究

在采用复模铸造工艺制备孔径d=2.5~3.50 mm,孔隙率P=56.8%~86.1%通孔多孔铝的基础上,通过单轴压缩试验,研究了通孔多孔铝的压缩性能和吸能能力。通孔多孔铝单轴压缩应力-应变曲线,呈现线弹性变形、平缓塑性变形和压缩紧实3个阶段。通孔泡沫铝的压缩屈服强度、吸能能力随孔隙率增大而减小,采用Gibson-Ashby的模型拟合通孔多孔铝的压缩屈服强度。     

占位法制备球形孔泡沫铝的结构与性能研究

以氯化钙、硬脂酸、硫代硫酸钠、尿素作为造孔剂,利用占位法进行孔径为1～2 mm,孔隙率为60%、70%、80%球形孔泡沫铝的制备。对其孔结构(孔面积、孔圆形度)、压缩性能和吸能效果进行对比分析。结果表明：氯化钙-泡沫铝因其具备较好的孔结构,所表现出的压缩性能和吸能效果也更优异。     

胞状AlCu5Mn合金泡沫的压缩性能和能量吸收特性

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.     

盐球渗透铸造法制备开孔泡沫铝的孔结构及压缩性能

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)。     

The synthesis,compressive properties,and applications of metal matrix syntactic foams

Metal matrix syntactic foams are composites that incorporate hollow particles in a matrix, where enclosing porosity inside the thin shell of the particle leads to low density without large decreases in mechanical properties. Studies on Al, Mg, Pb, and Zn alloy matrix syntactic foams are available in the published literature. A large stress plateau region appears in the compressive stress-strain graphs of metal matrix syntactic foams. The height and length of stress plateau can be tailored by means of particle wall thickness, volume fraction, and size, and the total compressive energy absorption can be controlled. Metal matrix syntactic foams seem promising in various energy absorbing applications including automobile parts since their energy absorption capability per unit weight is better than other foams and lightweight materials.     

泡沫镁宏微观结构表征及压缩性能研究

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Mg2Ca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。     

Sound absorption property of open-pore aluminum foams

The sound absorption property of aluminum foam was studied by testing its sound absorption coefficients using standing wave tube method. The open-pore aluminum foams were prepared by infiltration process, with pore size of 0.5 mm to 3.2 mm and porosity of 54.2% to 77%. The frequency of indicted sound wave was ranging from 125 Hz to 10 kHz. The results show that the average values of sound absorption coefficients are all over 0.4 and the aluminum foam has better sound absorption property, its coefficients is influenced by frequency and pore structure, and reaches the maximum at about 1 kHz, with increasing porosity and decreasing cell diameter the sound absorption coefficient values increase.     

Performance of stainless steel foams produced by infiltration casting techniques

Ferritic (AISI 430) and austenitic (AISI 304) stainless steel foams were produced exploiting a process based on molten metal infiltration on ceramic model. In particular, SiC foundry filter was used as space holder and, after the solidification, it has been removed by hydrofluoric acid. The produced foams are featured by three different porosity grades (10, 20 and 30 PPI) and by constant relative density (0.60). The morphology, the mechanical properties and the corrosion resistance were studied and the results were correlated to the material, the porosity, the size and the distribution of the voids. Morphologically, the structure is arboreous open-cell foam featured by interconnected cavities. This aspect, combined with the high relative density, assures high compressive plateau stress, structural integrity and good deformability. The corrosive tests, according to the ASTM A262-Met.B and NACE TM-0284, permitted to identify possible application fields for these products.     

Fabrication and compressive behavior of open-cell aluminum foams via infiltration casting using spherical CaCl2 space-holders

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.     

Preparation of porous Ti35Nb alloy and its mechanical properties under monotonic and cyclic loading

The Ti-35%Nb(mass fraction) foams were prepared by a powder metallurgy method,and the microstructure and the mechanical properties of the foams under monotonic and cyclic loading were investigated.The microstructure of the foams mainly consists of β phase,and the foams exhibit the homogenous pore distribution with the average pore size of 252 μm.The foams with 66% porosity show a typical stress-strain curve of the open-cell foams,and the plateau stress is about 56 MPa.The fatigue strength of the foam is 15.12 MPa at 107 cycles.The fractographic analysis of the foams reveals that the cracks nucleate within the struts and grow in a fatigue mechanism,resulting in the acceleration of the fatigue damage of the foams.     

泡沫钛制备及力学性能评价研究

利用占位体烧结法在不同的占位体粒径、体积分数以及不同的烧结温度、时间条件下制备出泡沫钛。采用光学金相、扫描电镜等对泡沫钛的孔隙结构进行分析;通过室温压缩实验对泡沫钛的力学性能进行评价。结果表明,泡沫钛孔隙横截面呈圆形,纵截面呈椭圆形,其孔隙率与占位体体积分数的差值随占位体粒径、体积分数的增加、烧结温度的升高、时间的延长呈升高的变化趋势。同时,烧结温度越高,所制备的泡沫钛孔壁越致密。与传统的泡沫材料不同,泡沫钛应力-应变关系曲线并没有出现明显的应力平台,抗压缩强度和弹性模量随孔隙率的增加呈下降的变化趋势,当孔隙率为67.6%时,抗压缩强度和弹性模量分别达到14.4 MPa和1.17 GPa。抗压缩强度随孔径的增大呈先升高再降低的变化趋势,而弹性模量随孔径的增加基本不变,当孔径达到1.15～1.53 mm时,其抗压缩强度和弹性模量分别达到48.9 MPa和1.72 GPa。