基于表面层的微细薄板弯曲回弹预测建模与实验研究

基于微/介观材料尺度效应表面层模型,对薄板表面层材料和内部材料分层处理,在纯弯矩弯曲模型基础上,考虑受到表面层晶粒影响的材料本构尺度效应并引入薄板回弹计算,分别对表面层和内部材料进行分析求得弯曲弯矩,从而建立了考虑尺度效应的微细薄板弯曲回弹预测模型。为了讨论模型的准确性,对不同晶粒、不同介观尺度的纯铜薄板开展了弯曲回弹的实验研究,实验结果表明,对于同一厚度的试样,薄板弯曲回弹角随着试样晶粒尺寸的增大而减小,对于不同厚度而晶粒尺寸相近的试样,回弹角随着试样厚度的增大而减小。分别利用传统回弹模型和考虑尺度效应的预测模型计算了弯曲回弹角,与实验结果对比发现,本文建立的模型能更准确地预测介观条件下微细薄板弯曲回弹现象。     

C5210磷青铜薄板成形行为的尺度效应（英文）

为研究厚度、晶粒尺寸对C5210磷青铜薄板力学性能和成形性能的影响,通过不同温度退火热处理得到不同晶粒尺寸的试样,然后在常温下对具有不同厚度和晶粒尺寸的试样进行单向拉伸试验。结果表明:当厚度在50~800μm范围内,材料的屈服强度随着厚度的减小而增大,而加工硬化指数和伸长率随着厚度的减小而减小,提出了描述屈服强度随厚度减小而增大关系的修正模型;材料的屈服强度随着晶粒尺寸的增大而减小,但加工硬化指数随着晶粒尺寸的增大而增大,伸长率则随着晶粒尺寸的增大先增大到一个峰值后再减小。通过扫描电镜观察拉伸试样的断口形貌发现所有试样断裂方式均为韧性断裂,并且随着厚度的增大断口韧窝的密集度增大,而晶粒尺寸越大的试样断口韧窝密集度越小。     

工业纯铝在室温和深冷轧制条件下的微尺寸效应

对1060工业纯铝分别进行室温轧制和深冷轧制,取成品厚度为300、200、100、50和25μm 5组试样进行拉伸试验。结果表明,经过室温轧制的轧件,当其厚度减薄至100μm时出现微尺寸效应,即厚度大于100μm时随厚度减小抗拉强度增大,厚度小于100μm时随厚度减小抗拉强度减小;发现100μm是纯铝室温轧制时出现尺寸效应的临界值。与室温轧制相比,经过深冷轧制轧件微尺寸效应的临界值相同而表现形式不同,厚度小于临界值100μm后其抗拉强度随厚度减小而增加的速度加快。在相同厚度条件下,深冷轧制后的轧件比室温轧制的晶粒内部亚结构更细小,分析认为这是其强度高于室温轧制的一个原因。     

304不锈钢微成形表层晶粒影响行为研究

在微塑性成形过程中,虽然零件的宏观尺寸达到了毫米或微米级,但其微观组织却没有发生明显的变化,材料的表层晶粒尺寸也就越来越趋近零件的几何尺寸,导致塑性成形规律呈现出与宏观大尺寸零件不同的尺寸效应现象。对四种厚度的304不锈钢薄板试样进行了单向拉伸试验和微弯曲试验,测量了薄板的厚度。结果表明,随着薄板厚度的减小,塑性变形区内表层晶粒的位错滑移变化对力学性能和无量纲弯矩的影响越来越显著,表现出"越薄越强"的尺寸效应现象。引入修正的Hall-Petch公式与修正的Nix-Gao应变梯度模型,使力学性能和无量纲弯矩的预测和试验结果吻合。     

微细薄板尺度依赖的材料本构模型的构建(英文)

通过表面层理论和金属晶体塑性变形原理解释微细薄板材料在塑性变形中产生尺寸效应的内在机理。引入尺度参数,对经典的Hall-Petch公式进行修正,建立基于表面层模型理论的尺度依赖材料模型。利用所建立的材料模型分析微细薄板厚度及其晶粒尺寸对材料成形流动性能的影响。在晶粒尺寸一定的情况下,随着微细薄板厚度的减小,材料流动应力逐渐降低;晶粒尺寸越大的微细薄板,其流动变形的尺寸效应现象越明显。利用不同厚度的不锈钢和纯铜箔材的微细薄板拉伸真应力-应变曲线对所建立的材料模型进行验证,计算结果与实验结果比较吻合,验证了所建立的材料模型的合理性。     

黄铜薄板单向拉伸第Ⅱ类尺寸效应

以黄铜薄板为研究对象,通过对不同厚度、不同宽度试样的单向拉伸,研究厚度和宽度变化对薄板单向拉伸过程应力和塑性性能的影响。实验结果表明,厚度变化对应力的影响十分显著。当厚度小于10倍左右内禀尺寸,薄板变形不均匀性加剧,不断增大的几何必需位错加强了薄板的硬化,流动应力随厚度的减小而增大,表现出明显的第Ⅱ类尺寸效应。但是当应变增大到0.013以后,几何必需位错所占比例不断减小,其对材料的硬化作用明显减弱。此外,随着厚度的减小,薄板的断裂机制由韧窝微孔聚集断裂转变为沿晶断裂,板料的塑性性能持续下降。拉伸试样宽度减小使流动应力略微下降,但对塑性性能影响不大。     

微细黄铜板料尺寸效应

为研究微细尺度下材料的晶粒尺寸d、厚度t对其力学性能的影响,引入尺寸效应影响因子φ=t/d,在常温下对具有不同晶粒尺寸和板厚的H62黄铜薄板试样进行单向拉伸实验。结果表明,随着φ的减小,流动应力减小,延伸率下降;板料硬化指数n值,随板料厚度的增加而增大,随晶粒尺寸的增大而增大。拉伸试样均为韧窝微孔聚合型断裂,0.5mm和1.0mm厚度试样断口处韧窝多而浅,且为抛物线形,材料韧性好,塑性强;板厚0.1mm和0.2mm的试样断口韧窝深而大,硬化指数n值大,但塑性差。     

微细C5210磷青铜板料的尺寸效应研究

为研究常温下晶粒尺寸和厚度对C5210磷青铜力学性能的影响,引入尺寸效应影响因子φ=厚度/晶粒尺寸。结果表明,厚度不同时,随着φ从14.7减小到6.3,屈服强度减小了48%,延伸率由25.5%减小到18.2%;晶粒尺寸不同时,随着φ的减小,屈服强度先快速下降,当φ减小到3.5后便缓慢下降,延伸率则先增大再减小,φ为3.5时延伸率达到最大值29.2%。通过扫描电镜观察拉伸试样断口,均为韧性断裂。厚度不同时,随着φ的增大,韧窝数量增多且尺寸增大,材料塑性较好;晶粒尺寸不同时,φ从10.6减小至3.5,断面收缩率增加,韧窝尺寸增大,材料塑性较好。而当φ值继续减小到0.8时,韧窝数量减少,且尺寸变小,材料的塑性变差。     

7075-T651铝合金表面纳米化处理及其强化机理

通过表面机械滚压处理(SMRT)方法实现了7075-T651铝合金表面的纳米化。电子背散射衍射(EBSD)研究表明,SMRT后的试样表层形成了梯度纳米层:表层纳米晶粒层厚度约为50μm,平均晶粒尺寸约为200 nm;亚表层变形晶粒层厚度约为450μm,平均晶粒尺寸约为2μm,母材呈现出典型的轧制晶粒特征,平均晶粒尺寸约为5μm。拉伸试验结果表明,SMRT后试样的强度得到了显著提高,塑韧性也没有明显下降。通过SMRT在材料的表层引入了梯度纳米结构,这种特殊结构具有较为优秀的强度和塑性的匹配,是力学性能提升的主要原因。     

黄铜箔拉伸屈服强度的尺寸效应

为了研究金属箔的塑性变形性能与尺寸的相关性,在常温下对不同厚度和晶粒尺寸的黄铜箔试样进行了单向拉伸实验.结果表明:随着厚度或晶粒尺寸的减小,箔的屈服强度都会升高,晶粒尺寸对屈服强度的影响满足Hall-Petch细晶强化关系,厚度减小使屈服强度升高也可以主要归结于晶粒尺寸的减小.此外,当箔的厚度小于100 靘时,厚度/晶粒尺寸比不能表征屈服强度的尺寸效应.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.