烧结温度对多孔TiNi合金微观结构和力学性能的影响

采用Ti、Ni纯元素混合粉末真空烧结技术制备了孔隙分布均匀且力学性能优良的多孔TiNi形状记忆合金(SMA),并利用X射线衍射仪、金相显微镜、扫描电子显微镜及电子万能试验机研究对比了900、950、1000、1050、1100和1150℃6个不同烧结温度对合金微观结构和力学性能等的影响。结果表明,烧结温度是影响多孔TiNi合金性能的决定性因素,通过调节烧结温度可有效调节合金的相组成、孔隙特征和力学性能。随着烧结温度的升高,合金的次生相逐渐减少,相组成成分更加均一;致密度不断提高,由59%上升到62%,孔隙分布愈加均匀且孔隙形貌由多尖角形趋于球形化;抗拉强度由72.43MPa增加到160.12MPa,弹性模量从1.08GPa增加到1.32GPa。     

多孔Ti-Nb-Zr合金的孔隙特征与力学性能

合金的多孔化是降低合金弹性模量最有效的方式之一,采用气氛管式炉烧结制备添加不同含量的造孔剂的TiNb24Zr4合金,通过光学显微镜、SEM、XRD、三点弯曲实验以及压缩试验测定合金孔隙率,分析孔隙形貌和试样的力学性能.通过分析,该多孔合金为近β型钛合金,通过控制造孔剂的添加量来控制合金的孔隙度及其孔隙特征,可以根据此关...     

多孔医用Ti-24Nb-4Zr-8Sn合金的制备和力学性能

将轧制成形与真空烧结相结合制备出大块多孔Ti-24Nb-4Zr-8Sn(%,质量分数,简称Ti2448)材料,研究了冷轧形变量(20%-40%)和烧结温度(1100-1300℃)对其孔隙率、平均孔径、压缩强度及杨氏模量的影响。结果表明,在烧结温度相同的情况下,随着冷轧形变量的增加,多孔Ti2448合金的孔隙率和平均孔径均减小,压缩强度和弹性模量线性增加。烧结温度对多孔材料孔隙率及孔径的影响不大。在孔隙率相同的情况下,多孔Ti2448合金的压缩强度和模量比明显优于纯钛多孔材料。     

Ag含量对表面多孔Ti-Ag/NiTi梯度合金组织与性能的影响

为了提高NiTi合金的生物活性并赋予其一定的抗菌性,采用放电等离子烧结技术制备了表面多孔Ti-Ag /NiTi梯度合金,利用X射线衍射(XRD)、光学显微镜(OM)、扫描电镜(SEM)、室温压缩、人工模拟体液浸泡、贴膜法等方法研究了不同Ag含量对梯度合金微观组织、界面结合、表面孔隙特征、力学性能、体外生物活性及抗菌性能的影响及机理.研究表明：梯度合金中间基体主要由奥氏体NiTi相(B2)和单斜马氏体NiTi相(B19′)组成,并同时存在少量次生相Ti₂Ni相,表面多孔层主要由α-Ti、TiAg和Ti₂Ag相组成,内外层界面形成稳定冶金结合;Ag含量增加对梯度合金表面孔隙率和平均孔径影响不大,但抗压强度值提高而弹性模量变化不明显,这主要与表面多孔层中TiAg和Ti₂Ag相的强化作用有关;梯度合金在人工模拟体液中浸泡14 d后表面形成了大量类骨磷灰石层,显示了优异的体外生物活性,同时,Ag的加入显著提高了梯度合金的抗菌性能.     

粉末粒度对蒙乃尔合金多孔材料压缩性能的影响

烧结蒙乃尔合金多孔材料是重要的金属过滤材料之一,凭借其优良的耐高温抗腐蚀及良好的抗冲击、可焊接等优势广泛应用于化工、核工业、石化等诸多领域.随着蒙乃尔过滤材料应用领域的拓展及使用环境越来越苛刻,其力学性能的研究显得尤为重要.采用粉末冶金法制备(O)20mm×25mm柱状压缩试件,利用MTS810对这些试件进行力学性能测试,采用准静态单一轴向的加载方式对试样进行压缩性能的测试,并详细分析了相同孔隙度下粒度对镍合金多孔材料压缩性能的影响,结果表明,镍合金多孔材料的压缩应力-应变曲线有塑性材料的特征;对于同一孔隙度的试样,弹性模量和屈服强度都随着粒度的减小而增加,当粒度<75μm时,屈服强度和弹性模量增加得很快.     

造孔剂对新型医用多孔Ti-14Mo-2.1Ta-0.9Nb-7Zr合金组织性能的影响

合金多孔化是有效降低材料弹性模量的方式之一,采用添加造孔剂的元素粉末冶金法制备了新型医用多孔Ti-14Mo-2.1Ta-0.9Nb-7Zr合金,通过扫描电镜、阿基米德法、X射线衍射和压缩力学性能测试的方法研究了不同造孔剂用量和粒径尺寸对合金形貌特征、孔隙率、物相组成及力学性能的影响规律。结果表明:该方法制备所得多孔Ti-14Mo-2.1Ta-0.9Nb-7Zr合金为近β型钛合金;随着造孔剂用量增加,平均孔径无变化,孔隙率呈线性增长,弹性模量和抗压强度减小,其中弹性模量的变化满足线性关系;随着造孔剂粒径尺寸增加,平均孔径增大而孔隙率基本不变,抗压强度和弹性模量减小;添加20%(质量分数)粒径尺寸为125~200μm的NH4HCO3造孔剂制备多孔Ti-14Mo-2.1Ta-0.9Nb-7Zr合金,于1300℃烧结4h孔隙率达到38.9%并含有贯穿孔结构,抗压强度达到405 MPa,而弹性模量为9.19GPa,能满足医用植入材料的要求。     

尿素含量对Ti-10%Mg多孔材料孔隙结构和抗压性能的影响

以尿素为造孔剂,采用粉末冶金法在630℃真空条件下烧结制备Ti-10%Mg多孔材料,研究了造孔剂含量对其孔隙结构、物相成分、孔隙率及抗压性能的影响。研究表明,造孔剂含量为25%(w)时,烧结体的孔隙大小均匀,主要相为Ti和Mg,造孔剂添加量未对其物相产生明显影响;随着造孔剂含量的增加,烧结体的孔隙率随之增加,抗压强度和弹性模量随之降低;Ti-10%Mg多孔材料的抗压强度和弹性模量分别为16~183MPa和1.87~10.15 GPa,理论上可以作为人体骨骼的替代材料。     

电弧增材成型铝合金的组织及力学性能

研究了2319铝合金冷金属过渡焊电弧增材成型试样沉积态及热处理态的显微组织、力学性能，以及不同温度对弹性模量的影响。结果表明：沉积态纵向试样的抗拉强度比横向试样小9.3%,纵向试样的抗拉强度存在各向异性；热处理后，试样的抗拉强度提高了约35%,纵向试样的抗拉强度仍然存在各向异性；热处理后，纵向试样和横向试样的弹性模量基本一致，随着试验温度的升高，弹性模量均呈下降趋势。     

多孔ZnO/羟基磷灰石生物复合材料的制备与性能

利用放电等离子烧结技术制备多孔ZnO/羟基磷灰石（HA）生物复合材料,研究不同纳米ZnO含量对ZnO/HA复合材料微观结构、孔隙特征、力学性能、矿化和降解性能的影响。结果表明:烧结后ZnO/HA复合材料主要由HA相和ZnO相组成;随着ZnO含量提高,多孔ZnO/HA复合材料孔隙率缓慢增大,抗压强度略有减小,弹性模量变化不大;多孔ZnO/HA复合材料的孔隙率>40%,孔径在50～500 μm之间,抗压强度>148 MPa,弹性模量为6.5 GPa左右,能够满足骨修复材料的要求;模拟人工体液中矿化和降解实验表明,多孔ZnO/HA复合材料浸泡7天后表面开始形成大量类骨磷灰石层,且随着ZnO含量增加,磷灰石形成能力明显增强而降解速率加快。      

表面多孔Ti-羟基磷灰石/Ti-Ag生物梯度复合材料的制备与性能

采用放电等离子烧结技术制备表面多孔Ti-羟基磷灰石（HA）/Ti-Ag生物梯度复合材料,研究了不同HA含量对复合材料微观结构、界面结合、表面孔隙特征、力学性能及体外生物活性的影响及机制。结果表明,表面多孔Ti-HA/Ti-Ag复合材料中间基体合金主要由α-Ti和Ti₂Ag相组成,表面多孔层主要由α-Ti和HA相组成,同时还存在少量CaO、CaTiO₃、Ti₅P₃等反应相;表面多孔Ti-HA/Ti-Ag复合材料中间基体与表面多孔层形成稳定的冶金结合,但随着HA含量增加,反应相增多,界面结合变差,表面孔隙率和平均孔径呈增大趋势,导致平均抗压强度减小且弹性模量降低,因此过高的HA含量会导致材料力学性能下降;体外生物活性实验表明,表面多孔Ti-HA/Ti-Ag复合材料在人工模拟体液中浸泡7天后表面生成大量类骨磷灰石层,并且随着HA含量的增大,磷灰石形成能力明显增强。      

Prediction of bending strength of long corrugated boxes

Long corrugated boxes were supported at both ends and bent by a concentrated force applied at the middle. Boxes with different lengths, cross‐sectional shapes, flute directions and board strengths were tested, using a standard compression tester with a fixed platen in accordance with ASTM D‐642. An equation was developed to relate compression strength to the various properties of the box. The correlation coefficient R² for the fit to actual data was about 0.4. Boxes having the flutes run around the box had a 20% higher compression strength than with horizontal flutes. The most significant factor was found to be the board edge crush strength. The results suggest that failure of boxes in bending is due to localized crushing at the point of application of the load, rather than whole‐box collapse. Copyright © 2001 John Wiley & Sons, Ltd.     

The effect of adding nano-SiO2 and nano-Al2O3 on properties of high calcium fly ash geopolymer cured at ambient temperature

This article presents the effect of adding nano-SiO₂ and nano-Al₂O₃ on the properties of high calcium fly ash geopolymer pastes. Nano-particles were added to fly ash at the dosages of 0%, 1%, 2%, and 3% by weight. The sodium hydroxide concentration of 10 molars, sodium silicate to sodium hydroxide weight ratio of 2.0, the alkaline liquid/binder ratio of 0.60 and curing at ambient temperature of 23 °C were used in all mixtures. The results showed that the use of nano-SiO₂ as additive to fly ash results in the decrease of the setting time, while the addition of nano-Al₂O₃ results in only a slight reduction in setting time. Adding 1–2% nano-particles could improve compressive strength, flexural strength, and elastic modulus of pastes due to the formation of additional calcium silicate hydrate (CSH) or calcium aluminosilicate hydrate (CASH) and sodium aluminosilicate hydrate (NASH) or geopolymer gel in geopolymer matrix. In addition, the additions of both nano-SiO₂ and nano-Al₂O₃ enhances the shear bond strength between concrete substrate and geopolymer.     

新型4层瓦楞纸板的性能分析

研究了一种新型的4层瓦楞纸板结构,并将4层瓦楞纸板和3层、5层瓦楞纸板的平压强度、边压强度、戳穿强度和耐破度性能进行比较,最后得到新型4层瓦楞纸板的主要优点是:厚度比5层瓦楞纸板要薄,节省了夹芯纸的用量,降低瓦楞纸板的成本,而且强度高,在一定情况下可以代替5层瓦楞纸板达到抗压、防震、缓冲的目的。     

The role of 0–2 mm fine recycled concrete aggregate on the compressive and splitting tensile strengths of recycled concrete aggregate concrete

The aim of this study is to investigate the role of 0–2 mm fine aggregate on the compressive and splitting tensile strengths of recycled concrete aggregate (RCA) concrete with normal and high strengths. Normal coarse and fine aggregates were substituted with the same grading of RCAs in two normal and high strength concrete mixtures. In addition, to keep the same slump value for all mixes, additional water or superplasticizer were used in the RCA concretes. The compressive and splitting tensile strengths were measured at 3, 7 and 28 days. Test results show that coarse and fine RCAs, which were achieved from a parent concrete with 30 MPa compressive strength, have about 11.5 and 3.5 times higher water absorption than normal coarse and fine aggregates, respectively. The density of RCAs was about 20% less than normal aggregates, and, hence, the density of RCA concrete was about 8–13.5% less than normal aggregate concrete. The use of RCA instead of normal aggregates reduced the compressive and splitting tensile strengths in both normal and high strength concrete. The reduction in the splitting tensile strength was more pronounced than for the compressive strength. However, both strengths could be improved by incorporating silica fume and/or normal fine aggregates of 0–2 mm size in the RCA concrete mixture. The positive effect of the contribution of normal sand of 0–2 mm in RCA concrete is more pronounced in the compressive strength of a normal strength concrete and in the splitting tensile strength of high strength concrete. In addition, some equation predictions of the splitting tensile strength from compressive strength are recommended for both normal and RCA concretes.     

Yield strength in submicrovolumes of single crystals

The specificity of the transition from elastic to elastoplastic deformation in defect-free single crystals during the localization of the deformation in a submicron region has been studied by nanoindentation. A sharp transition from elastic to elastoplastic deformation has been observed in tested single crystals at depths of about 20–50 nm. To define the yield strength using the nanoindentation data, the stressed-strained state in the contact region has been analyzed. It has been shown that the yield strength in submicrovolumes of single crystals is tens-hundreds times higher than that at the macroscopic level and approaches the value of the theoretical shear strength. A mechanism of the transition from elastic to elastoplastic deformation has been discussed in the framework of the phenomenological model of the nucleation of dislocations. The transition has been induced by the homogeneous nucleation of dislocations in a contact.     

A practical model for efficient anti-fatigue design and selection of metallic materials:Ⅰ.Model building and fatigue strength prediction

The high cost and low efficiency of fatigue tests are bottleneck problem for the anti-fatigue design of metallic materials.For this problem,a theoretical fatigue model is proposed in this study,the possible applications have also been discussed.Specific results would be introduced in two serial papers,in which the first paper focuses on the model building and the applications on fatigue strength prediction;the second paper put emphasis on the influencing factors of the model parameters and the applications on fatigue strength improvement.In this first paper,a theoretical model is proposed considering both the strength and plastic restrictions of fatigue strength.As the model builds up a brief relationship among yield strength(Y),tensile strength(T)and fatigue strength(F),it is named as the Y-T-F model.Through the verification with fatigue strength data covering various kinds of metallic materials and loading condi-tions,this Y-T-F model exhibits both generality and accuracy.With the Y-T-F model,the efficient fatigue strength prediction could be conducted by brief linear fitting and calculation,just through yield strength,tensile strength and several known fatigue strength data.Moreover,through its deduced Y-F model,the analytical formula of fatigue strength continuously changing with materials strengthening can be obtained,as well as the maximum value of fatigue strength and corresponding critical yield strength.In summary,the Y-T-F model would be useful for reducing the fatigue tests,thus providing new possibilities on the efficient anti-fatigue design and selection of metallic materials.     

Concrete with ceramic waste aggregate

Use of hazardous industrial wastes in concrete-making will lead to greener environment. In ceramic industry about 30% production goes as waste, which is not recycled at present. In this study an attempt has been made to find the suitability of the ceramic industrial wastes as a possible substitute for conventional crushed stone coarse aggregate. Experiments were carried out to determine the compressive, splitting tensile and flexural strengths and the modulus of elasticity of concrete with ceramic waste coarse aggregate and to compare them with those of conventional concrete made with crushed stone coarse aggregate. The properties of the aggregates were also compared. Test results indicate that the workability of ceramic waste coarse aggregate concrete is good and the strength characteristics are comparable to those of the conventional concrete.     

碳/铝复合材料界面结合强度对拉伸性能的影响

本文主要研究C/Al复合材料先驱丝的界面结合强度的表征方法以及界面结合状态对复合材料拉伸性能的影响.用自行研制的小型剪切试验机测定复合材料先驱丝的纵向剪切强度,通过计算得到复合材料界面处的剪切强度以此作为界面结合强度的定量表征方法.实验证明,不同界面结合强度的复合丝在宏观上表现出有不同纵向剪切强度值,复合材料的界面结合强度可以用界面剪切强度值定量描述.复合材料拉伸强度随界面强度提高而减少,在满足复合材料横向强度要求前提下,降低复合材料界面结合有利于提高拉伸强度.     

High-Cycle Fatigue of Materials and Parts of Gas-Turbine Engines

We present a historical survey of the development of the scientific direction called “Structural Strength” at the Central Institute of Airplane Engine Manufacturing (CIAEM) for the last 30 years in connection with the 100th birthday of Academician S. V. Serensen, founder of this direction in the USSR, and the 75th anniversary of foundation of the CIAEM. We present the principal results obtained by the scientific staff of the Sector of Fatigue Strength of Materials of Gas-Turbine Engines at the CIAEM.__________Translated from Problemy Prochnosti, No. 3, pp. 5 – 21, May – June, 2005.     

膨胀螺栓与混凝土拉拔力的测试和分析

叙述了膨胀螺栓与混凝土拉拔力的设计准则和试验方法,并对影响拉拔性能的因素进行了分析和评价。