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A combined experimental and crystal plasticity study of grain size effects in magnesium alloys

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Journal of Magnesium and Alloys 2023年第12期11卷 4445-4467页

作者： Aaditya Lakshmanan Mohsen Taheri Andani Mohammadreza Yaghoobi John Allison Amit Misra Veera Sundararaghavan Department of Aerospace Engineering University of MichiganAnn ArborMI48105USA Department of Materials Science and Engineering University of MichiganAnn ArborMI48105USA Department of Mechanical Engineering University of MichiganAnn ArborMI48105USA

This work presents a method to incorporate the micro hall-petch equation into the crystal plasticity finite element(CPFE) framework accounting for the microstructural features to understand the coupling between grain size, texture, and loading direction in magnesium alloys.The effect of grain size and texture is accounted for by modifying the slip resistances of individual basal and prismatic systems based on the micro hall-petch equation. The modification based on the micro hall-petch equation endows every slip system at each microstructural point with a slip system-level grain size and maximum compatibility factor, which are in turn used to modify the slip resistance. While the slip-system level grain size is a measure of the grain size, the maximum compatibility factor encodes the effect of the grain boundary on the slip system resistance modification and is computed based on the Luster-Morris factor. The model is calibrated using experimental stress-strain curves of Mg-4Al samples with three different grain sizes from which the hall-petch coefficients are extracted and compared with hall-petch coefficients predicted using original parameters from previous work. The predictability of the model is then evaluated for a Mg-4Al sample with different texture and three grain sizes subjected to loading in different directions. The calibrated parameters are then used for some parametric studies to investigate the variation of hall-petch slope for different degrees of simulated spread in basal texture,variation of hall-petch slope with loading direction relative to basal poles for a microstructure with strong basal texture, and variation of yield strength with change in grain morphology. The proposed approach to incorporate the micro hall-petch equation into the CPFE framework provides a foundation to quantitatively model more complicated scenarios of coupling between grain size, texture and loading direction in the plasticity of Mg alloys.

关键词： hall-petch Crystal plasticity Grain size Texture Magnesium alloys

The combined effects of grain and sample sizes on the mechanical properties and fracture modes of gold microwires

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Journal of Materials Science & Technology 2019年第1期35卷 76-83页

作者： H.K.Yang K.Cao Y.Han M.Wen J.M.Guo Z.L.Tan J.Lu Y.Lu Hong Kong Branch of National Precious Metals Material Engineering Research Center City University of Hong Kong Department of Mechanical and Biomedical Engineering City University of Hong Kong State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals Sino-platinum Metals Co.Ltd Center for Advanced Structural Materials City University of Hong Kong Shenzhen Research Institute

hall-petch relation was widely applied to evaluate the grain size effect on mechanical properties of metallic material. However, the sample size effect on the hall-petch relation was always ignored. In the present study, the mechanical test and microstructure observation were performed to investigate the combined effects of grain and sample sizes on the deformation behaviors of gold microwires. The polycrystalline gold microwires with diameter of 16 ?m were annealed at temperatures from 100°C to 600°C, leading to different ratios(t/d) of wire diameter(t) to grain size(d) from 0.9 to 16.7. When the t/d was lower than 10, the yield stress dropped fast and deviated from the hall-petch relation. The free-surface grains played key role in the yield stress softening, and the volume fraction of free-surface grains increased with the t/d decreasing. Furthermore, the effects of t/d on work-hardening behaviors and fracture modes were also studied. With t/d value decreasing from 17 to 3.4, the samples exhibited necking fracture and the dislocation pile-ups induced work-hardening stage was gradually activated.With the t/d value further decreasing(t/d < 3.4), the fracture mode turned into shear failure, and the work-hardening capability lost. As the gold microwire for wire bonding is commonly applied in the packaging of integrated circuit chips, and the fabrication of microwire suffers multi-pass cold-drawing and annealing treatments to control the grain size. The present study could provide instructive suggestion for gold microwire fabrication and bonding processes.

关键词： Gold microwire Wire bonding Tensile testing Grain size hall-petch relationship

Evolution of microstructure and hardness in a dual-phase Al0.5CoCrFeNi high-entropy alloy with different grain sizes

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Rare Metals 2020年第2期39卷 156-161页

作者： Hao-Xue Yang Jin-Shan Li Tong Guo William-Yi Wang Hong-Chao Kou Jun Wang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China

Cold-rolling with subsequent annealing was carried out to produce recrystallized structures with different grain sizes in an Al0.5CoCrFeNi high-entropy alloy to systematically investigate the grain growth behavior and varying properties.The results show that recrystallized microstructures can be achieved through an annealing process at 1200℃for 75 min to 16 h,and the average grain size in this study ranges from 5.33 to 30.03 μm.The hardness shown to be affected through grain coarsening was then measured as a function of the grain size,and it is found to follow the classical hall-petch strengthening.

关键词： High-entropy alloy Grain growth Recrystallization Grain boundary hall-petch effect

Collinear micro-shear-bands model for grain-size and precipitate-size effects on the yield strength

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Theoretical & Applied Mechanics Letters 2018年第4期8卷 245-251,298页

作者： Yike Qiu Peng Zhang Lifeng Ma S&V Lab Department of Engineering Mechanics Xi'an Jiaotong University Xi'an Thermal Power Research Institute Co. Ltd

Numerous experimental evidences show that the grain size may significantly alter the yield strength of metals.Similarly,innickel-based superalloys,the precipitate size also influences their yield strength.Then,how to describe such two kinds of size effects on the yield strength is a very practical challenge.In this study,according to experimental observations,a collinear micro-shear-bands model is proposed to explore these size effects on metal materials’yield strength.An analytical solution for the simple model is derived.It reveals that the yield strength is a function of average grain-size or precipitate-size,which is able to reasonably explain size effects on yield strength.The typical example validation shows that the new relationship is not only able to precisely describe the grain-size effect in some cases,but also able to theoretically address the unexplained hall-petch relationship between theprecipitate size and the yield strength of nickel-based superalloys.

关键词： Collinear micro-shear-bands model The hall-petch relationship γprecipitate Size effect

Fe-based Nanocrystalline Alloy Containing a Small Amount of Transition Elements

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Chinese Science Bulletin 1993年第21期38卷 1772-1774页

作者：刘学东王景唐 State Key Laboratory of RSA Institute of Metal Research Academia Sinica Shenyang 110015 PRC

Recently, polycrystalline materials with nanometer-size grains have aroused great interest since researchers have found that the interface component cannot be ignored in these materials, and the existence of a large number of interfaces leads to variation of many properties related to the microstructural characteristics, such as the hall-petch relation reported in Refs.[1, 2]. Lu et al. developed a new method for synthesizing bulk nanocrystalline alloys by using the amorphous crystallization, i. e. by

关键词： nanocrystalline alloy microhardness hall-petch relation

Effect of Ti content on the yield strength of Nb-Ti microalloyed steels

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Baosteel Technical Research 2009年第4期3卷 53-55页

作者： YUAN Xiangqian JIAO Sihai Metallurgical Process Division Research Institute Baoshan Iron ＆ Steel Co. Ltd. Shanghai 201900 China

The hot rolling experiment investigates into the relationship between the microstructures and the mechanical properties of Nb-Ti microalloyed steels with various Ti contents. The results indicate that the effect of the bainite fraction of Nb-Ti microalloyed steels on the yield strength of the steels is not related to Ti content, while the slope of the hall- petch relationship decreases with the increase of Ti content. Accordingly, the Misra model for the yield strength of Nb-Ti microalloyed steels is modified, and the factors which cause the change in the slope of hall-petch relationship are discussed.

关键词： Nb-Ti microalloyed steel yield strength hall-petch

Mechanical Properties of Micro- and Nanostructured Copper Films

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Journal of Materials Science and Chemical Engineering 2013年第5期1卷 7-10页

作者： N. Kosarev M. Khazin R. Apakashev N. Valiev The Ural State Mining University Ekaterinburg Russia

Mechanical properties of electrodeposited and electroless copper with nano- and crystalline structure are considered. Grain diameters in films ranged from 0.06 to 8 μm. A model is described which takes into account t... 详细信息

关键词： Nano- and Microcrystalline Materials hall-petch Relation Yield Point Stress Grain Boundary Hardening Coefficient Nonequilibrium Grain Boundaries

多弧离子镀制备TiAlN-Cu多层膜的组织结构和性能研究

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多弧离子镀制备TiAlN-Cu多层膜的组织结构和性能研究

作者：吴雨晴燕山大学

学位级别：硕士

在传统的硬质薄膜中Ti Al N由于具有高硬度、高温抗氧化性(800℃)和高温热稳定性(达1470℃)已取代了Ti N薄膜,并广泛应用于机械领域中的刀具、模具和切削工具等部件上。Cu由于具有优良的塑性和延展性常加入到薄膜中以改善薄膜的综合性... 详细信息

在传统的硬质薄膜中Ti Al N由于具有高硬度、高温抗氧化性(800℃)和高温热稳定性(达1470℃)已取代了Ti N薄膜,并广泛应用于机械领域中的刀具、模具和切削工具等部件上。Cu由于具有优良的塑性和延展性常加入到薄膜中以改善薄膜的综合性能。为了提高Ti Al N薄膜的综合力学性能,本课题在Ti Al N薄膜中加入不同厚度的Cu层,研究Cu层在Ti Al N-Cu多层膜中所起的作用,并与Ti Al N薄膜相比较,薄膜的硬度、膜基结合强度、韧性以及耐磨性是否有所提高。为了揭示多层膜的强韧化机制和耐磨性,对不同厚度Cu层的Ti Al N-Cu多层膜力学性能和摩擦磨损性能的影响进行了研究,并从理论上分析了Cu层厚度对多层膜综合性能的影响。本课题采用BY-DH-4A型多弧离子镀设备进行沉积制备薄膜,首先试验出沉积Ti Al N薄膜最优参数。采用Ti Al合金靶和Cu磁过滤靶交替沉积制备Ti Al N-Cu多层膜,为了提高薄膜膜基结合力,在衬底与薄膜之间增加一薄层Ti Al过渡层。选择实验参数:脉冲偏压为-100V,靶电流为90A,进行沉积Ti Al N-Cu多层膜,沉积Ti Al N在N2放电条件下,其工作气压为0.5Pa,沉积Cu层在Ar放电条件下,工作气压为0.3Pa,制备的Ti Al N-Cu多层膜为三层膜结构,Cu为中间层。通过实验研究和理论分析,多层膜结构可以影响薄膜的内残余应力,进而影响薄膜的硬度、膜基结合强度等力学性能。本论文对Ti Al N薄膜和不同Cu层厚度Ti Al N-Cu多层膜的力学性能研究表明,当Cu层厚度在81nm时,Ti Al N-Cu多层膜硬度值最高,当Cu层厚度大于81nm时,Ti Al N-Cu多层膜硬度反而迅速下降,低于Ti Al N薄膜硬度。根据纳米多层结构效应,当调制层厚(λ)在纳米范围内,材料强度不遵循hall-petch公式,材料硬度会达到一峰值,之后随着厚度增加硬度迅速下降;而当调制层厚在微米范围内,材料强度遵循hall-petch公式。Cu层厚度也是影响Ti Al N-Cu多层膜力学性能的关键因素之一。当增加的Cu层厚度在纳米范围内时Ti Al N-Cu多层膜的硬度比Ti Al N薄膜有硬度优势。本实验测得Ti Al N-Cu多层膜在韧性、膜基结合强度上都高于Ti Al N薄膜。本实验还测得Ti Al N-Cu多层膜的表面粗糙度临界值。根据Ti Al N-Cu多层膜表面粗糙度与摩擦系数的关系可得到Ti Al N-Cu表面粗糙度的临界值为0.12μm,符合Svahn等人的研究结论,低于这个临界值,表面粗糙度对薄膜的摩擦系数影响不大,而高于这个临界值,表面粗糙度对薄膜的摩擦系数影响很大。本论文还研究了Ti Al N薄膜和不同Cu层厚度Ti Al N-Cu多层膜的摩擦磨损性能。研究发现不同Cu层厚度的Ti Al N-Cu多层膜有不同的结合力也有不同的磨损类型。当Cu层厚度大于108nm,Ti Al N-Cu多层膜的磨损率低于单一Ti Al N薄膜的磨损率,有更好的耐磨性。根据涂层膜基结合力的高低对应着不同的摩擦副和磨损类型可知:结合力最高硬度值最低的Ti Al N-Cu多层膜有着最低摩擦系数和磨损率,对应粘着磨损;结合力与硬度值居中的Ti Al N-Cu多层膜属于疲劳磨损类型;而结合力较低硬度值最高的Ti Al N-Cu多层膜有着最高的摩擦系数和磨损率,对应三体磨粒磨损;而Ti Al N薄膜由于其表面脱落的Ti Al N硬质颗粒以及低的结合力所以磨痕属于磨粒磨损和粘着磨损的混合磨损。通过本课题的研究,通过适当加入Cu层中间层可以改变单一Ti Al N薄膜机械性能。当Cu层厚度在纳米尺寸内,Ti Al N-Cu多层膜的硬度增高。Cu层厚度在100nm范围的Ti Al N-Cu多层膜的膜基结合力、韧性以及耐磨性要远远好于单一的Ti Al N薄膜。这对以后实际生产和机械领域中的应用,比如刀具、模具及切削工具等部件使用,有很好的利用和参考价值,以及对研究多层膜的结构和性能有重要的研究价值。

关键词：硬质薄膜 TiAlN-Cu多层膜多弧离子镀 hall-petch