不同材料冠状动脉支架膨胀行为分析

冠状动脉支架作为经皮穿刺冠状动脉成形术中保持病变血管畅通的核心器件,其在手术过程中受球囊作用的扩张特性以及球囊撤出后的反弹行为对支架植入术的成功有着重要的影响.利用有限元的方法系统,建立专有支架单独膨胀和血管支架膨胀模型,分析了316L不锈钢和L605钴铬合金两种材料支架筋尺寸和支架扩张尺度的变化及血管对其膨胀行为的影响.结果显示,支架所选材料是决定支架膨胀行为的主要因素,L605材料支架所需的临界内压力及反弹行为明显大于316L不锈钢支架;材料一定时,增加支架筋的宽度或厚度提高支架迅速扩张临界内压力;支架轴向长度的变化只与结构和最终膨胀状态相关.有限元模拟对支架性能的评价和设计有一定指导意义.     

选择性激光烧结工艺制备的钴铬合金的微观结构

对比选择性激光烧结工艺(SLM)和铸造工艺(cast)制备的Co-Cr合金的内部微观结构,分析产生不同微观结构的原因,并分析不同微观结构对Co-Cr合金性能可能造成的影响。选取组成接近的Co-Cr合金金属粉末和金属块,分别通过SLM工艺和cast工艺制作Co-Cr合金试样。利用场发射扫描电镜(SEM)观察样品内部的微观结构并采用X射线能谱(EDX)分析样品特征区域的化学成分。SLM工艺制备的样品的内部结构均匀,没有出现分相区,而离心cast工艺和真空cast工艺制备的样品内部均出现富含Mo元素的分相区。SLM工艺和cast工艺制备的样品的孔洞均较少。对于Co-Cr合金而言,SLM工艺的加工质量优于cast工艺。     

离子液体中电沉积钴铬合金析氢性能研究

为了研究电沉积合金材料的析氢性能,本文在离子液体中通过脉冲电沉积法在碳钢上制备钴铬合金,研究了离子液体中电沉积不同的钴盐浓度对析氢过电位的影响,并与离子液体中电沉积的Co电极和Cr电极,水溶液中电沉积的Co-Cr合金电极进行了对比分析。利用三电极体系测试沉积电极在碱性环境下的电化学性能,采用线性极化法、方波电位法、交流阻抗法、恒电流电解法等电化学测试方法,并结合XRD、SEM、EDS进行了形貌、物相与元素分析。实验结果表明：制备的Co-Cr合金是多晶的,其晶粒尺寸为12.3 nm;当电流密度为10和100 mA/cm²时,所对应的析氢过电位分别为-105和-408 mV;当塔菲尔斜率为-0.228 V/dec时,析氢电阻为2.45Ω,计算得到其微观表面积为647 cm²;合金中Cr的质量分数约为8.5%,Co的质量分数约78.5%。随着钴盐浓度的上升,电沉积的钴铬合金电极的析氢性能越来越好。在离子液体中,通过脉冲电沉积制备的Co-Cr合金电极具有出色的电化学析氢性能,析氢机理为析氢反应动力学中的Volmer-Heyrovsky反应机理,析氢性...     

碳质生物材料的界面现象

要更多地了解碳/碳化硅(C/SiC)复合材料在生理环境中的反应,界面现象的研究极为重要。本研究选用了Ti-6Al-4V,316L不锈钢、Ocr18Ni9Ti不锈钢,Co-Cr—Mo合金,骨水泥和C/SiC作为植入材料、采用光学显微镜(LM)和配有X-光能谱议(EDAX)的扫描电镜(SEM)对界面特性进行了观测,综合结果指出,C/SiC复合材料具有优良的骨组织相容性。     

高熵合金研究的新进展

介绍了高熵合金这一全新的合金设计概念.由于高熵合金由超过5种主元构成,因此具有许多有别于传统合金的组织和性能.概述了高熵合金的定义、特性以及相关热力学原理,重点介绍了最近3年来国内外在高熵合金领域取得的实质性进展.并展望了高熵合金在工业上的应用前景.     

激光选区熔化技术制备高熵合金的研究进展（英文）

高熵合金的多组分特性使其具有许多传统合金无法比拟的优异性能.然而,高熵合金传统的制备方法仍存在一定的局限性.激光选区熔化(SLM)技术可以通过逐层沉积的方式实现复杂零件的精密成形.将SLM技术与高熵合金相结合,可以充分发挥高熵合金的性能优势.本文综述了SLM制备的高熵合金的显微结构和性能特征.由于SLM工艺存在高温梯度和高冷却速率,所以在SLM制备的高熵合金中通常会形成复杂的微观结构,包括胞状亚结构、析出相、层错和纳米孪晶.此外,独特的微观结构为高熵合金带来了优异的力学性能和其他功能,表明利用SLM技术制备高熵合金具有很大的发展潜力.此外,我们还简要介绍了SLM制备的高熵合金的微观缺陷及其应用.本文为高性能高熵合金的设计提供了有益的指导.     

高熵合金功能特性研究进展

传统合金大多以一种主元为基础,通过添加少量或微量特定元素形成不同类型的合金来改善材料的综合性能,但这显然限制了它们新性能的发展.因此,必须开发非常规合金以满足日益增长的需求.高熵合金(High-entropy alloys,HEAs)是近年来发现的一种新型多组元金属材料,因具有独特的设计理念、组织结构以及优异的性能,其在短短数年内获得了大量科研工作者的关注.相较于传统合金注重于相图的边界(顶点、边缘)区域,HEAs则侧重于多组元相图靠近中心的区域,因此HEAs有着更加广阔的成分设计空间.与传统金属材料相比,高熵合金还展现出卓越的力学性能和良好的功能特性.当前关于HEAs的报道大都集中在成分设计规则以及材料的微观结构和力学性能方面,并在成分设计和变形机制等方面取得了显著进展,然而关于高熵合金功能性质的开发和理论的研究还十分有限.基于此,本文简要介绍了高熵合金的发展历程,系统总结了高熵合金的制备方法,分析了高熵合金耐蚀性能和耐磨性能的研究现状,并对其影响因素进行了重点讨论,还探讨了高熵合金在软磁、抗辐照、催化剂、生物医用材料等领域的发展现状,最后对高熵合金当前的研究难点和未来发展进行了探讨和展望,以期为研究人员开展功能HEAs的研究提供参考.     

ZL205A合金高强优质铸件在大飞机上的应用

本文综述了高强ZL205A合金铸造特性、成分和性能特点,介绍了该合金优质铸件在飞机、导弹等武器上的应用,对大飞机设计时选用ZL205A合金优质铸件提出几点体会.     

非晶态合金镀层在弹药包装的应用探讨

非晶态合金镀层作为一种功能镀层具有优良的电磁、静电防护性能,以及优良的物理化学性能.从化学镀基础理论出发,对化学镀实现非晶态合金镀层的各种性能做了介绍,最后提出化学镀非晶态合金镀层技术在弹药包装上应用的可行性.     

SiGe系热电材料的研究动态

半导体材料的热电效应在温差发电领域存在着巨大的潜力,但如何提高材料的热电转化效率是目前研究探讨的热电问题.重点介绍了提高SiGe合金热电性能的途径,以及硅锗合金的特性和热电性能的测试方法及以后研究的方向.     

VC/Cr3C2添加剂与烧结温度对超细WC-12Co硬质合金的影响

为了有效控制烧结过程中WC晶粒的长大,获得高强度高硬度的超细硬质合金,采用扫描电镜、拉伸机和洛氏硬度仪研究了不同质量分数及配比的VC/Cr3C2晶粒长大抑制剂和烧结温度对超细WC-12Co硬质合金的显微组织及力学性能的影响,并结合试验结果分析了超细硬质合金中VC/Cr3C2晶粒长大抑制剂的作用机理.结果表明,添加适量VC/Cr3C2晶粒长大抑制剂的超细硬质合金中WC晶粒尺寸分布集中,不存在明显的组织缺陷,合金具有细而均匀的微观组织及优异的力学性能.当晶粒长大抑制剂(质量分数)为0.2%VC/0.5%Cr3C2,1450℃烧结制备WC-12Co超细硬质合金的抗弯强度为3710MPa,硬度(HRA)为91.5.VC/Cr3C2晶粒长大抑制剂的作用机理为:VC主要与WC反应生成(W,V)C固溶体聚集在WC/Co界面,降低WC/Co界面能,Cr3C2主要固溶在粘结相中,导致WC在粘结相中的溶解度降低,二者的综合作用减缓了粘结相中WC溶解-析出过程,从而抑制烧结过程中WC晶粒的长大.     

Investigation of WC–Co alloy properties based on thermodynamic calculation and Weibull distribution

The influence of alloy composition and sintering temperature on the mechanical properties and reliability of WC–Co cemented carbides was studied theoretically and experimentally. For the first time, through a hybrid approach of thermodynamic calculations and Weibull distribution, the comprehensive performance of ultrafine WC–Co cemented carbides with different C contents and inhibitor type was investigated in detail. The carbon content of WC–10?wt-% Co–0.5?wt-% Cr cemented carbides was carefully controlled within the range of 5.38?5.52?wt-%. The contents of Cr and V are chosen to be in the range of 0–1?wt-%. It is found that WC–10?wt-% Co–0.5?wt-% Cr alloys with 5.46?wt-% C or 5.5?wt-% C show excellent mechanical properties and high reliability. WC–10?wt-% Co alloys with 0.5?wt-% Cr and 0.4?wt-% Cr–0.2?wt-% V demonstrate high mechanical property and reliability. The results of this study can be used to design process parameters during the manufacture of WC–Co cemented carbides.     

Insights into Phase Evolution and Mechanical Behavior of the Eutectoid Ti–6.4(wt%)Ni Alloy Modified with Fe and Cr

Titanium alloys gain increasing importance in industry due to the expansion of advanced manufacturing technologies such as additive manufacturing. Conventional titanium alloys processed by such technologies suffer from formation of large primary grains and anisotropy of mechanical properties. Therefore, novel alloys are required. Herein, the effect of ternary alloying elements Fe and Cr on the Ti–6.4(wt%)Ni eutectoid system is investigated. Both elements act as eutectoid formers. Fe and Cr show sluggish transformation behavior, whereas Ni is an active eutectoid-forming element. Thereby, sluggish refers to slow and active to fast transformation kinetics. The focus of this work is on the combined addition of such elements studied under different heat-treatment conditions. It is shown in the results that largely varying microstructures can be generated resulting in hardness values ranging from 239 to 556 HV_0.1. Moreover, the formation of a substructure within the α phase of direct aged alloys is observed. The formation mechanism of this substructure is investigated in detail. The mechanical properties are discussed based on the microstructural characteristics. The presence of intermetallic Ti₂Ni phase increases the Young's modulus, whereas the presence of ω phase results in embrittlement. The results shed light upon the complex phase formation and decomposition behavior of titanium alloys based on Ti–6.4Ni.     

Characterisation of detonation sprayed Mo–Co–Cr–B alloy coatings

Abstract

A novel thermal spray material of Mo–Co–Cr–B with high durability in molten alloys has been developed to utilise for die casting parts and for galvanising bath parts. In the present paper, detonation gun (D gun) spray technique was used to deposit a Mo–Co–Cr–B alloy coating onto 316L stainless steel substrate, and the microstructures and mechanical properties of the coating system were studied using XRD, SEM, tensile test and Vickers microhardness. The results show that the microstructures of the coating consisted of ternary transition metal borides matrix CoMo₂B₂, CoMoB, as well as a little amount of binary borides, MoB and CrB. The ternary borides matrix contained both amorphous phase and nanocrystalline grains with a size of 60±35 nm. The bond strength of the coating decreases with increasing thickness of the as sprayed coatings. The anisotropy in the mechanical properties between the cross-section and plan section of the coatings is examined. Comparing the microhardness and bond strength of detonation sprayed Mo–Co–Cr–B coating with those of HVOF sprayed Mo–Co–Cr–B coating, it can be concluded that the detonation spray process has a better performance than HVOF spray process.     

High-entropy FeNiCoCr alloys with improved mechanical and tribological properties by tailoring composition and controlling oxidation

Many metal matrix self-lubricating composites possess excellent comprehensive properties of high strength and wear resistance after incorporating various lubricants that usually belong to ceramic phase.However,this improvement is always obtained at the cost of notable decrease in toughness.In order to break through this toughness-tribological properties trade-off,self-lubricating composite alloys based on the matrix of FeNiCoCr0.5 high entropy alloy(HEA)were prepared by milling addition of element Co or Cr and then spark plasma sintering(SPS).Co or Cr is added into the base HEA with the aim of tailoring oxidation behavior,mechanical properties as well as tribological performances.As no ceramic lubricants are used,the alloy composites remain high toughness.Co or Cr element addition leads to the precipita-tion of a hard phase of σ-Cr and grain refinement,both of which contribute to the increase of mechanical strength.On sliding,oxidation of Fe and Ni is suppressed.Instead,the oxides of cobalt and chromium are formed upon the Co-and Cr-modified HEAs,respectively.These oxidation products,especially the oxides of cobalt that are easy to be sintered on sliding,are in favor of the formation of a lubricating glaze layer at 400℃on the worn surface,and thus the decrease in friction coefficient and wear rate,which are 0.33 and 4.0×10-5 mm3/(N m),respectively.     

Long-term biodegradation and associated hydrogen evolution of duplex-structured Mg-Li-Al-(RE) alloys and their mechanical properties

Preliminary in vivo tests of two magnesium alloys, i.e. AE21 and WE43, as biodegradable vascular stent materials, have yielded encouraging results. However, their degradation is desired to be prolonged, mechanical stability over a defined time improved and ductility needed for stent expansion enhanced. A search for alternative magnesium alloys that can better meet these clinical requirements is needed. The present research aimed to evaluate the long-term degradation behavior, hydrogen evolution rates and mechanical properties of three lithium-containing magnesium alloys, namely LA92, LAE912 and LAE922 with a duplex crystal structure, in comparison with those of a WE-type alloy. Immersion tests in Hank's balanced salt solution for 600 days showed that the LA92 alloy degraded much less than the LAE912 and the LAE922 alloys. It even outperformed the WE-type alloy after immersion for 94 days. Moreover, unlike the other three alloys investigated, the LA92 alloy displayed a steady hydrogen evolution rate over the whole period of immersion tests. In addition, it possessed an elongation value of 33%, being much higher than the WE-type alloy. Thus, this alloy has a greater potential of meeting the requirements of radially expandable stents in mechanical properties and degradation performance.     

Structure and mechanical properties of as-cast Ti–5Nb–xCr alloys

As-cast Ti–5Nb and a series of Ti–5Nb–xCr with Cr content ranging from 1 to 13 mass% prepared by using a commercial arc-melting vacuum-pressure casting system were investigated. Commercially pure titanium (c.p. Ti) was used as a control. X-ray diffraction (XRD) for phase analysis was conducted with a diffractometer. Three-point bending tests were performed to evaluate the mechanical properties of all specimens. The fractured surfaces were observed by using scanning electron microscopy (SEM). The experimental results indicated that these alloys obviously had different structures and mechanical properties with the addition of various amounts of Cr. When 1 mass% Cr was added, the structure was comprised mainly of the α′ phase, which was also found in Ti–5Nb. With the addition of 3 mass% Cr, α′ and α′′ phases were appeared. When the Cr content was increased to 5 mass% or greater, the β phase was completely retained. Moreover, the ω phase was detected in the Ti–5Nb–5Cr and Ti–5Nb–7Cr alloys. The largest quantity of ω phase and the highest bending modulus were found in the Ti–5Nb–5Cr alloy, while the Ti–5Nb–9Cr alloy had the lowest bending modulus. Moreover, the high strength/modulus ratios of the Ti–5Nb–3Cr (22.5) and Ti–5Nb–9Cr (21.3) alloys demonstrate its advantage for use as implant materials. Also, these two alloys exhibited the better elastic recovery angles of 28.3° in Ti–5Nb–3Cr and 22.2° in Ti–5Nb–9Cr. In the current search for better implant materials, α′ + α′′ phase Ti–5Nb–3Cr and β phase Ti–5Nb–9Cr alloys with low modulus, ductile property, excellent elastic recovery capability and reasonably high-strength seem to be the most feasible alloy for orthopedic and dental applications if some other necessary properties are obtained.     

高强度Cu基块状非晶合金的最新研究进展

Cu基块状非晶合金是一种新型高性能材料,从合金体系、力学性能、合金过冷液体区域的性能及非晶形成能力几方面对Cu基块状非晶合金的最新研究进展进行了综述,并展望了新型Cu基块状非晶合金的工程应用前景.     

Role of alloying elements in microstructures of beta titanium alloys with carbon additions

Abstract

The effect of 0.2 wt-%C on the microstructure of beta titanium alloys Ti-15X(Fe, Cr, Mn, Mo, Ni, Co, Cu, and V) has been studied using scanning and transmission electron microscopy. It has been found that coarse eutectic TiC_x tends to be formed in beta titanium alloys containing Fe, Cr, Mo, and Mn, and relatively finer homogeneous TiC_x is formed in alloys containing V, Ta, Co, Ni, or Cu. The volume fraction of TiC_x in alloys containing Cu, Co, and Ni is much less than that in other beta titanium alloys. The oxygen content of the matrix is lower than that of Ti₂C in Cr or alloys containing Mn and higher than that of Ti₂C in alloys containing Mo or Ni. These observations are discussed in terms of the role of phase diagrams and the effect of atomic radius of alloying elements on the dimension of interstitial sites in the host alloy and the sublattice of TiC_x.