共查询到19条相似文献,搜索用时 578 毫秒
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剧烈塑性变形(SPD)能使材料同时具有良好的力学性能和优良的生物相容性能。与传统的钛合金相比,超细晶生物医用钛合金具有更高的强度、更好的耐腐蚀性和抗疲劳性能。重点论述了剧烈塑性变形技术及其在医用钛合金中的应用,详细地阐述了4种SPD细化晶粒方法。 相似文献
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综述了锆及锆合金剧烈塑性变形(SPD)后性能变化的研究进展,系统阐述了锆及锆合金经剧烈塑性变形后显微硬度、拉伸/压缩性能、高低周疲劳性能,重点介绍了SPD技术在纯锆、Zr-Nb系合金中的应用。经过剧烈塑性变形后,锆及锆合金的抗拉强度及屈服强度均显著提升,但依据剧烈塑性成形轨迹、合金成分、第二相分布、热处理制度不同,其提升程度存在一定的差别。位错滑移是锆及锆合金高周疲劳的主要损伤机制,位错运动(包括位错滑移及位错攀移)是锆及锆合金低周疲劳的主要损伤机制。文章最后指出现阶段锆及锆合金SPD技术的发展趋势及应用前景。 相似文献
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首先,对表面完整性的基本概念和内涵进行了概述,同时简要介绍了超声实现滚压技术的基本原理及其优点。随后,对比分析了不同剧烈塑性变形方法的特点和局限性,引出了实现表面完整性的相关剧烈塑性变形协调机制。在此基础上,随后结合其他剧烈塑性变形强化工艺,重点总结了超声滚压剧烈塑性变形对金属材料表面微观结构演变的影响。具体探讨了剧烈塑性变形诱导晶粒细化机制、晶粒生长机制以及合金元素偏聚机制等,主要分别论述了不同层错能的面心立方、体心立方以及密排六方等不同金属晶体结构的晶粒细化机制(以位错滑移、变形孪晶为主导)、晶粒长大机制(以晶界迁移、晶粒旋转为主要)与合金元素偏聚机制(晶界偏聚、位错核心偏聚)等。最后,对以上内容进行了综合总结,并针对超声滚压技术研究中存在的问题给出进一步研究和发展的建议,从而为实现超声滚压金属材料的表面完整性的主动精准控制及提高其服役寿命与可靠性提供一定的参考。 相似文献
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纳米高强Ti-Nb-Zr-Sn合金 总被引:8,自引:0,他引:8
在常见的应变速率范围内,多数金属材料的冷加工变形主要是通过位错增殖、形变孪晶或马氏体相变等机制实现,这些变形机制无法有效地细化晶粒,通常只有采用剧烈塑性变形方法制备无缺陷的金属纳米材料.最近在研究β型Ti-Nb—Zr-Sn钛合金形变过程时,发现塑性失稳导致局域化非均匀塑性变形对品粒细化具有显著作用;利用该变形机理,采用常规冷轧方法即可以轧制出厚度为1.5mm板材,其品粒尺寸小于50nm.本文主要论述该合金冷加工组织细化过程和时效强化机理,并讨论非均匀塑性变形方式的可能原因. 相似文献
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目的通过改变喷丸的压力或时间,在钛合金表面制备出剧烈塑性变形(SPD)层较厚、硬度较高的梯度纳米晶结构。方法改变喷丸压力(0.3~0.6 MPa)或喷丸时间(15~60 min),调控TC4钛合金表面梯度纳米晶结构的变形层厚度和纳米晶晶粒尺寸。利用金相显微镜观察塑性变形层截面的组织形貌,通过X射线衍射仪(XRD)和透射电子显微镜(TEM)确定喷丸表面纳米晶的晶粒尺寸,通过显微硬度计对塑性变形层的截面硬度进行研究。结果一定喷丸压力(0.6MPa)下,SPD层和总变形层厚度分别在喷丸25、30 min时达到饱和值78μm和143μm。一定喷丸时间(25 min)下,SPD层和总变形层的厚度随喷丸压力的增加而增厚,在0.4 MPa时达到饱和,分别为78μm和120μm。当SPD层厚度进入饱和阶段后,表层晶粒大小和硬度强化程度都趋于稳定;在0.6 MPa下,当表面α相细化至稳定阶段时,晶粒尺寸为30~90 nm,表面硬度提高约30%。结论喷丸SPD层及总变形层的厚度随喷丸时间的延长或喷丸压力的增大而增厚,当SPD层厚度趋于饱和后,表面晶粒尺寸和硬度强化程度都已饱和。 相似文献
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剧塑性变形制备超细晶/纳米晶结构金属材料的研究现状和应用展望 总被引:5,自引:1,他引:4
综合目前剧塑性变形方法制备超细晶及纳米晶结构金属材料的研究现状,介绍等通道转角挤压、高压扭转、累积叠轧焊、多向锻造等剧塑性变形方法及其特点与原理;探讨剧塑性变形金属材料的组织演变和晶粒细化机制;分析金属材料经剧塑性变形后强度与延展性的变化趋势,及其对超塑性变形的影响规律;展望剧塑性变形方法对金属材料应用的前景。 相似文献
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Terry C. Lowe Ruslan Z. Valiev 《JOM Journal of the Minerals, Metals and Materials Society》2004,56(10):64-68
Severe plastic deformation (SPD) has emerged as a promising method to produce ultrafine-grained materials with attractive
properties. Today, SPD techniques are rapidly developing and are on the verge of moving from lab-scale research into commercial
production. This paper discusses new trends in the development of SPD techniques suchas high-pressure torsion and equal-channel
angle pressing, as well as new alternative techniques for introducing SPD. The paper also contains a comparative analysis
of SPD techniques in terms of their relative capabilities for grain refinement, enhancement of properties, and potential to
economically produce ultrafine-grained metals and alloys.
For more information, contact Terry C. Lowe, Science and Technology Base Programs, Los Alamos National Laboratory, Los Alamos,
NM 87545; (505) 667-7824; fax (505) 665-3199; e-mail tlowe@lanl.gov. 相似文献
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The microstructure development during plastic deformation was reviewed for iron and steel which were subjected to cold rolling
or mechanical milling (MM) treatment, and the change in strengthening mechanism caused by the severe plastic deformation (SPD)
was also discussed in terms of ultra grain refinement behavior. The microstructure of cold-rolled iron is characterized by
a typical dislocation cell structure, where the strength can be explained by dislocation strengthening. It was confirmed that
the increase in dislocation density by cold working is limited at 1016m−2, which means the maximum hardness obtained by dislocation strengthening is HV3.7 GPa. However, the iron is abnormally work-hardened
over the maximum dislocation strengthening by SPD of MM because of the ultra grain refinement caused by the SPD. In addition,
impurity of carbon plays an important role in such grain refinement: the carbon addition leads to the formation of nano-crystallized
structure in iron. 相似文献
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Asymmetric rolling(ASR), as one of severe plastic deformation(SPD) methods, was widely used to make ultra-fined materials with enhanced performance. Internal marks were used to show the shear deformation during asymmetric rolling with pure aluminium as a model material. Effects of reduction ratio and mismatch ratio on the shear deformation were studied. With the observed shear deformation results, equivalent strain was calculated. For lager shear deformation, rolling equipment was modified to increase friction between specimen and the rollers. Consequently, extremely fine grains with size of 500 nm are obtained in pure aluminium. With improved asymmetric rolling, the ability of grain refinement of ASR is greatly improved. 相似文献
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大体积超细晶金属材料的剧烈塑性变形法制备技术 总被引:3,自引:1,他引:2
介绍了大体积超细晶金属材料的各种常见剧烈塑性变形法制备技术,系统阐述了各种制备技术的基本原理,并分析比较了这些制备技术的优缺点和适用范围,指出了剧烈塑性变形法制备技术的发展方向。 相似文献
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《Acta Materialia》2008,56(7):1619-1632
With the aim of investigating the factors that limit the production of true nanograined materials by cryogenic severe deformation, the grain structures formed in an Al–0.1%Mg alloy have been studied in plane strain compression at temperatures down to 77 K, following prior severe plastic deformation (SPD) by equal channel angular extrusion. Changing the deformation mode alone had little effect on increasing the rate of grain refinement. At the minimum cryogenic temperature (77 K) the samples still contained ∼30% low angle boundaries and a nanoscale high-angle boundary (HAB) spacing was only obtained in one dimension. At high strains a steady-state minimum HAB spacing was approached, irrespective of the temperature, where the rate of grain refinement stagnated. It is shown that the minimum grain size achievable in SPD is limited by a balance between the rate of compression of the HAB spacing and dynamic grain coarsening. At low temperatures this is controlled by abnormally high boundary migration rates, which are difficult to explain with existing theories of grain boundary mobility. 相似文献
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Grain refinement during severe plastic deformation (SPD) is predicted using volume averaged number of dislocations generated. The model incorporates a new expansion of a model for hardening in the parabolic hardening regime, in which the work hardening depends on the effective dislocation-free path related to the presence of non-shearable particles and solute–solute nearest-neighbour interactions. These two mechanisms give rise to dislocation multiplication in the form of generation of geometrically necessary dislocations and dislocations induced by local bond energies. The model predicts the volume averaged number of dislocations generated and considers that they distribute to create cell walls and move to existing cell walls/grain boundaries, where they increase the grain boundary misorientation. The model predicts grain sizes of Al alloys subjected to SPD over two orders of magnitude. The model correctly predicts the considerable influence of Mg content and content of non-shearable particles on the grain refinement during SPD. 相似文献