铜及其合金梯度结构制备及性能研究进展

高性能铜及铜合金由于其高导电性、高导热性、高强度、高耐蚀及可镀性、易加工性等系列优良特性而成为多个领域开发中必不可少的材料。研究发现,梯度结构的存在可有效提高铜及铜合金的强度,同时保持原有的塑性。区别于传统铜及其合金,表面细晶到心部粗晶的逐渐过渡及位错缺陷等的相互作用使梯度结构铜表现出更好的强塑性协同效应,正是这种异质性促使材料性能进一步提升。然而,基于梯度结构材料的异质性,传统铜及其合金的变形机制、制备技术及仿真模拟等并不适用于梯度结构铜及其合金,这使得梯度结构铜及其合金的实际生产应用受到极大限制。鉴于此,本文从梯度结构的制备工艺其性能改善方面综述了现有梯度结构铜及其合金的研究进展,梳理了诸多领域内梯度结构铜及铜合金材料的发展及现状,并分析了梯度结构铜合金材料的研究趋势与应用需求。     

晶粒尺寸梯度分布对316L不锈钢耐腐蚀性能的影响

采用表面机械碾压处理,在316L不锈钢表面制备出纳米晶-粗晶梯度过渡结构,对纳米晶、梯度区和粗晶区样品分别进行化学浸泡实验和电化学腐蚀实验,测试其腐蚀速率、腐蚀电位和点蚀电位等腐蚀性能参数,并对不同状态样品上钝化膜的形态、元素组成、织构及残余应力进行分析,研究晶粒尺寸梯度分布对316L不锈钢耐腐蚀性能的影响。结果表明,纳米晶和粗晶样品浸泡20 h出现稳定腐蚀坑,而梯度区样品浸泡50 h依然保持表面完整。腐蚀电位从纳米晶的-230 mV提高到梯度区的-4 mV,同时腐蚀电流从纳米晶的0.137 A/cm~2下降到0.036 A/cm~2。晶粒尺寸梯度分布不改变钝化膜形成动力学,梯度区表面钝化膜优异的耐蚀性能与其形成厚度较大、较完整致密且残余应力较小的钝化膜有关。     

纯铜表面纳米化的微观结构演化及其力学性能研究

利用表面机械滚压处理(surface mechanical rolling treatment, SMRT)工艺在纯铜表面制备出梯度纳米结构层,获得了最表层为取向随机的纳米晶粒、亚表层的晶粒尺寸在厚度方向上呈梯度分布的结构层。采用光学显微镜、扫描电子显微镜、透射电子显微镜对微观组织进行表征,研究了晶界、位错、孪晶界等微观结构的演化。通过改变SMART工艺参数,在纯铜表面制备出不同厚度的梯度纳米结构层,对比分析了梯度纳米结构层厚度对纯铜力学性能的影响。结果表明:经SMRT后,试样距表面大约5μm处的显微硬度高达1.56 GPa,其横截面的硬度随着距表面深度增加呈递减趋势;相比于粗晶铜,SMRT后纯铜的屈服强度提高了2倍多,而塑性损失很少,并且SMRT后纯铜的屈服强度随着梯度纳米结构层厚度的增加而提高。     

不锈钢的纳米化工艺及其耐腐蚀性

叙述了不锈钢表面纳米化技术-表面机械研磨处理,喷丸法,异步轧制法和激光表面融熔法和不锈钢块体纳米化技术-机械合金法,惰性气体凝聚原位加压法,电化学沉积法,非晶晶化法和大塑性变形法.纳米化不锈钢的耐蚀性能直接受到纳米晶结构的影响,结构均匀,无位错,无应力是获得优异耐蚀性的前提.     

钢铁材料表面自身纳米晶化及其应用前景

实现钢铁材料表面自身纳米晶化的主要方法有超声喷丸、高能喷丸和机械研磨处理等。大塑性变形诱发晶粒碎化和应变诱导相变是钢铁表面自身形成纳米晶的主要机制。表面自身纳米晶化能够显著提高钢铁材料的表面强度、硬度、耐磨和耐疲劳性能，在化学热处理和电化学防护方面展示了广阔的应用前景。     

机械合金化纳米晶材料研究进展

综述了机械合金化制备纳米晶材料的研究进展，重点介绍了高强度铝合金，铜合金，难熔金属化合物，金属储氢材料，复相烯土永磁材料等几类机械合金化纳米晶材料的制备与组织性能，指出了机械合金化技术在纳米晶材料制备方面的优势及应用前景。     

Al-Cu-Mn合金复合纳米结构构筑及强塑性机制研究

211ZX铝合金是新一代Al-Cu-Mn系耐热高强韧铝合金，为进一步提升该材料的室温成形性、力学性能和工业应用价值，通过形变热处理工艺在该合金中构筑了由超细晶、纳米晶、位错网状结构和纳米析出相组成的复合结构，使纳米薄板材的拉伸强度和塑性同时得到提高。该工艺包括固溶处理、室温多道次累积轧制变形和后续低温时效。相较于传统T6态，复合纳米结构使合金的屈服强度提升了～213 MPa，与大变形制备的211ZX铝合金纳米薄板材相比，该复合纳米结构使合金的均匀延伸率提升了～5%。通过X射线衍射仪（XRD）、激光共聚焦显微镜（CLSM）和透射电子显微镜（TEM）等微观结构表征，结合强化机制的分析，研究发现细晶强化和析出强化对具备复合结构薄板材的材料屈服强度贡献最大。借助硬度、拉伸曲线、断口截面TEM分析、位错密度及纳米析出相的演变规律分析，可以明确位错回复和高密度的纳米析出相是提升211ZX铝合金板材塑性的主要因素。     

超声波冲击对纯钛单轴拉伸性能的影响

<正>喷丸、喷砂、机械研磨、超声纳米表面改性、旋转超声喷丸及其他表面纳米化处理技术是近年来研究的热点。M.Wen等研究了利用机械研磨技术获得纯钛细晶的方法,S.Dai等通过高能喷丸将纯钛的屈服强度提高了150 MPa。但对于细晶化表面处理后纯钛在加载时变形机理的研究却很少见到报道。为了研究细晶纯钛单轴拉伸变形机理,俄罗斯国立托木斯克理工大学A.V.Panin等采用超声波冲击的方法制备细晶纯钛样品,并进行拉伸试验,借助于透射     

时效时间对表面机械研磨处理Cu-4.5Ti合金组织和硬度的影响

采用表面机械研磨法使Cu-4.5Ti合金表面形成纳米晶,利用X射线衍射分析,透射电子显微镜观察和显微硬度测量等手段研究时效时间对表面机械研磨处理Cu-4.5Ti合金组织和硬度的影响。结果表明:经过表面机械研磨处理后的Cu-4.5Ti合金发生了塑性变形,表层塑性变形明显,试样中出现了纳米晶结构,形成大量交割状态的机械孪晶;经过8 h时效处理后,试样中形成了更加致密的孪晶组织,并产生了更多孪晶区域。经表面机械研磨处理合金试样的显微硬度由表层向基体内部表现为先增大后减小的趋势,并最终达到稳定状态;经过8 h时效处理后试样到达峰值硬度,此时合金表层硬度增大至HV 213,并在离表层深度约50μm处获得HV 278的峰值硬度。     

Cu-Cr-Co-Ti合金微观组织和高温性能研究

采用真空感应熔炼结合两步低温轧制-时效处理（CRA）工艺制备了Cu-Cr-Co-Ti合金,分析了峰时效样品的室温性能和高温性能。通过电子背散射衍射（EBSD）和透射电子显微镜（TEM）观察了Cu-Cr-Co-Ti样品的微观组织。结果表明：两步低温轧制-时效处理能够在铜基体中引入高密度的变形孪晶片层、位错和纳米析出相,有效提升了Cu-Cr-Co-Ti合金的室温强度和导电率。具有面心立方结构的纳米Cr析出相均匀弥散地分布在铜基体内,和基体具有立方-立方位向关系。Co和Ti元素能够聚集在纳米Cr析出相表面上,阻碍了析出相在时效处理和高温变形过程的粗化和长大现象。在经过300 ℃高温拉伸测试后,纳米Cr析出相仍稳定地阻碍了晶界运动,显著提升了Cu-Cr系合金的高温性能。经过500 ℃时效处理2 h后,峰时效CRA样品的室温抗拉强度为571 MPa、导电率为73.9%IACS （国际退火铜标准）。高密度孪晶片层具有优异的热稳定性,将铜合金在300 ℃和400 ℃下的高温强度分别提升至481 MPa和379 MPa。     

热压温度对真空热压法制备Cu–30Ni–5Nb合金组织及性能的影响

采用真空热压法制备了Cu–30Ni–5Nb合金,研究了热压温度对合金组织、相对密度、熔点及热导率的影响。结果表明,在800～950 ℃热压温度范围内,Cu–30Ni–5Nb合金的熔点先降低后升高,900 ℃时铜合金的熔点最低（1178.92 ℃）;Cu–30Ni–5Nb合金的热导率先增大后减小,900 ℃时铜合金的热导率最大（30.65 W·m?1·K?1）。热压温度为875 ℃时,Cu–30Ni–5Nb合金具有较好的综合性能,相对密度为98.66%,熔点为1180.86 ℃,热导率为29.54 W·m?1·K?1,且合金屈服强度达到355.74 MPa,符合冷却水套的性能要求。     

Fatigue Life of Cast Titanium Alloys Under Simulated Denture Framework Displacements

The objective of the study was to evaluate the hypothesis that the mechanical properties and fatigue behavior of removable partial dentures (RPD) made from cast titanium alloys can be improved by alloying with low-cost, low-melting elements such as Cu, Al, and Fe using commercially pure Ti (CP-Ti) and Ti-6Al-4V as controls. RPD specimens in the form of rest-shaped, clasp, rectangular-shaped specimens and round-bar tensile specimens were cast using an experimental Ti-5Al-5Cu alloy, Ti-5Al-1Fe, and Ti-1Fe in an Al₂O₃-based investment with a centrifugal-casting machine. The mechanical properties of the alloys were determined by performing tensile tests under a controlled displacement rate. The fatigue life of the RPD specimens was tested by the three-point bending in an MTS testing machine under a cyclic displacement of 0.5 mm. Fatigue tests were performed at 10 Hz at ambient temperature until the specimens failed into two pieces. The tensile data were statistically analyzed using one-way ANOVA (α = 0.05) and the fatigue life data were analyzed using the Kaplan-Meier survival analysis (α = 0.05). The experimental Ti-5Al-5Cu alloy showed a significantly higher average fatigue life than that of either CP-Ti or Ti-5Al-1Fe alloy (p < 0.05). SEM fractography showed that the fatigue cracks initiated from surface grains, surface pores, or hard particles in surface grains instead of the internal casting pores. Among the alloys tested, the Ti-5Al-5Cu alloy exhibited favorable results in fabricating dental appliances with an excellent fatigue behavior compared with other commercial alloys.     

大塑性变形制备超细晶生物医用钛合金的研究进展

生物医用钛合金具有高强度、良好的耐蚀性能、较低的弹性模量、优异的生物相容性,已成为具有广阔应用前景的医用金属材料之一.与传统医用钛合金相比,超细晶医用钛合金具有更高的强度与更好的疲劳性能以及耐腐蚀性能.此外,超细晶钛合金可诱导骨组织向内生长,增加界面结合强度,加快骨修复进程,在硬组织修复材料领域具有广阔的应用前景.阐述了各种大塑性变形（Severe Plastic Deformation）法制备超细晶生物医用钛合金的研究状况与最新进展,指出了SPD法制备医用钛合金中存在的技术问题和发展方向,并展望了利用SPD法对生物医用钛合金改性将成为生物医用材料的研究热点.     

铁/镍基奥氏体多晶合金晶界弯曲研究进展

对于在高温环境服役的金属材料,晶界作为组织结构上的薄弱环节常常引发晶界裂纹而造成合金失效,严重影响了材料的高温力学性能表现。因而,如何改善晶界状态、提高晶界强度,是提高合金高温性能的关键。在铁/镍基奥氏体多晶合金中,采用晶界弯曲的方法强化晶界、改善合金性能一直受到国内外研究人员的广泛关注。从弯曲晶界的获得方法、形成机制及其对材料性能的影响3个方面概述了目前国内外的研究现状。较为全面地总结了特殊热处理与材料合金化等获得弯曲晶界的方法;讨论了不同合金中晶界第二相诱发晶界弯曲的驱动力和内在机理;介绍了弯曲晶界对材料力学性能、耐蚀性能及焊接性能的影响。最后,结合当前的研究现状,围绕弯曲晶界的形成条件和机制,以及弯曲晶界对性能的影响,提出了弯曲晶界未来的研究发展方向。      

Effects of trace ytterbium addition on microstructure,mechanical and thermal properties of hypoeutectic Al–5Ni alloy

Over the past decade, the cast aluminum alloys with excellent mechanical and conductivity properties have emerged as potential materials for thermal management. However, the traditional Al–Si based alloys are difficult to make significant breakthrough in conductivity performance. The hypoeutectic Al–5Ni alloy also possesses sound castability and is expected to be applied in thermal management applications. In this study, the effects of ytterbium (Yb element) at 0–0.5 wt% on the microstructures as well as the electrical/thermal conductivity and mechanical properties of the Al–5Ni alloy were systematically investigated. The experimental results indicate that the addition of Yb at a relatively low amount not only reduces the secondary dendrite arm spacing of the α-Al grains, but also modifies the morphology and distribution of eutectic boundary phase. Moreover, it is found that the dosage of Yb at 0.3 wt% in the Al–5Ni alloy can simultaneously improve the yield strength, ultimate tensile strength and electrical/thermal conductivity. The strengthening and toughening of the Al–5Ni alloy are mainly attributed to the decrease of secondary dendrite arm spacing and the improvement of eutectic phases. The transmission electron microscopy/selected area electron diffraction (TEM/SAED) analysis indicates that the ytterbium in Al–5Ni alloy will form Al₃Yb phase, which mainly agglomerates in the Al₃Ni phase region. This phase is helpful to decrease the solubility of impurity elements (e.g., Fe and Si) in the α-Al matrix, which is beneficial to electrical/thermal conductivity. The value of this study lays foundation for manufacturing Al–Ni alloys with high thermal conductivity and acceptable mechanical properties.     

粉末冶金铜铁合金的组织与性能

分别以元素混合粉、机械合金化粉和水气联合雾化合金粉为原料,结合冷等静压成形、烧结及轧制工艺制备了Cu?5％Fe合金(质量分数),对比了三种原料粉的铜铁合金粉末形貌、微观组织、力学性能及物理性能.结果表明,铁颗粒分布均匀,元素混合、机械合金化和水气联合雾化法粉末烧结体中铁颗粒平均尺寸分别为9.4μm、1.2μm、3.5μ...     

The fatigue behavior of fine grained two-phase alloys

The fatigue properties of a number of ultrafine grained two-phase alloys have been examined. Compositions and processing treatments were altered to produce volume fractions of the individual phases ranging from 0 to 100 pct along with changes in the grain sizes of the individual phases. In all two-phase alloys in this investigation, the second phase was distributed at grain boundaries rather than within the grains of the primary phase. The fatigue strengths of the two-phase microduplex alloys were generally higher than those of the corresponding single phase alloys. Tension-compression fatigue tests showed that a Coffin law type of fatigue relationship was obeyed in the low cycle fatigue tests. Fatigue crack growth rate studies in tension-tension on IN-744 sheet gave results very comparable to those reported for other steels. Fatigue cracks propagated through both phases without following any obvious crack paths and no indication of delamination or crack blunting was detected. The high cycle fatigue performance of microduplex alloys can be rationalized in terms of a critical crack opening displacement model for fatigue crack initiation. Formerly with the Interntional Nickel Company, Formerly with the Interntional Nickel Company,     

铜合金的腐蚀与防护研究进展

铜合金具有良好的导电性和导热性,是应用最广泛的工业材料之一。铜合金服役过程中常与酸、碱、盐等腐蚀介质接触,易引起铜合金的腐蚀,最终导致失效,对生产制造带来危害。提高铜合金的耐腐蚀性有利于进一步扩展其应用领域。本文主要归纳了Cr, Pb, Ti, Al,Mn, Ni以及稀土元素的添加对合金耐蚀性能的影响,通过合金元素的添加可以改变铜合金表面腐蚀产物膜的组成和形貌,减小相与相之间腐蚀电位差,以及减少有害杂质的存在,以此来改善铜合金的耐蚀性能。塑性变形和热处理是改善铜合金力学性能的常用手段,经塑性变形和热处理过后的铜合金,其微观组织形貌和分布发生了变化,因此对合金耐蚀性能也有一定的影响。本文主要从合金化、塑性变形及热处理3个方面对铜合金耐蚀性能影响进行综述,最后对铜合金的腐蚀防护研究进行总结和展望。     

Diffusion of Zn in Nanostructured Aluminum Alloys Produced by Surface Mechanical Attrition Treatment

After surface nanocrystallization of pure Al and a cast Al-Si alloy through surface mechanical attrition treatment (SMAT), 200- to 300-??m-thick Zn coatings were deposited on the nanostructured surface using the clod spray technique. Subsequently, diffusion of Zn into the Al substrate was induced by postspray annealing treatment at various temperatures for different times. The diffusion kinetics of Zn in the nanostructured surface layers was studied in terms of the Zn concentration profile in the substrate by using scanning electron microscopy (SEM) and electron probe microscopy analysis (EPMA). Experimental results show that not only the diffusivity of Zn in the nanocrystalline grains is significantly increased compared with the diffusion in the coarse grained counterpart, but the temperature at which noticeable Zn diffusion in Al alloys occurs is also reduced from 573?K (300?°C) in coarse-grained Al alloys to 523?K (250?°C) in nanostructured alloys. In addition, because the nanocrystalline grains produced by SMAT in Al-Si alloys are much smaller than those in pure Al due to the effect of eutectic Si, the diffusion of Zn in the SMATed Al-Si alloy is much faster than that in the SMATed pure Al. It is believed that the high diffusivity of Zn in the nanocrystalline Al grains is attributed to the large fraction of grain boundaries that act as fast diffusion channel. The effect of thermal stability of the nanocrystalline grains on Zn diffusion in the SMATed Al alloys is also discussed.