Creep Properties and Deformation Mechanisms of a FGH95 Ni-based Superalloy

By means of full heat treatment, microstructure observation, lattice parameters determination, and the measurement of creep curves, an investigation has been conducted into the microstructure and creep mechanisms of FGH95 Ni-based superalloy. Results show that after the alloy is hot isostatically pressed, coarse γ′ phase discontinuously distributes along the previous particle boundaries. After solution treatment at high temperature and aging, the grain size has no obvious change, and the amount of coarse γ′ phase decreases, and a high volume fraction of fine γ′ phase dispersedly precipitates in the γ matrix. Moreover, the granular carbides are found to be precipitated along grain boundaries, which can hinder the grain boundaries’ sliding and enhance the creep resistance of the alloy. By x-ray diffraction analysis, it is indicated that the lattice misfit between the γ and γ′ phases decreases in the alloy after full heat treatment. In the ranges of experimental temperatures and applied stresses, the creep activation energy of the alloy is measured to be 630.4 kJ/mol. During creep, the deformation mechanisms of the alloy are that dislocations slip in the γ matrix or shear into the γ′ phase. Thereinto, the creep dislocations move over the γ′ phase by the Orowan mechanism, and the $ \left\langle { 1 10 } \right\rangle $ 〈 1 10 〉 super-dislocation shearing into the γ′ phase can be decomposed to form the configuration of (1/3) $ \left\langle { 1 12 } \right\rangle $ 〈 1 12 〉 super-Shockleys’ partials and the stacking fault.     

High Temperature Creep Deformation Mechanisms of a Hot Corrosion-Resistant Nickel-based Superalloy

Creep properties of the experimental superalloy were investigated in the temperature range 1073–1223 K and stress range 110–550 MPa. The observations of dislocation structures during different creep conditions reveal that in the high stress region, particle-shearing mechanisms including stacking fault formation and antiphase boundary creation are operative and in the low stress region, the dislocation climb mechanism is dominant. From the plot of minimum creep rate versus applied stress, a very low stress region with exponent n < 2, which is related to diffusional creep, is found. Based on the experimental results, a stress–temperature creep deformation mechanism map for the alloy is constructed. On the basis of particle hardening theories and various dislocation-creep theories, the dislocation-creep transitions in terms of internal stress are discussed and calculated threshold stresses of various creep deformation mechanisms indicates that the particle shearing is easier to operate than Orowan looping at high stresses, and general climb is easy to happen at low stresses.     

基于神经网络的镍基高温合金蠕变断裂寿命研究

利用人工神经网络，使用BP算法对镍基高温合金蠕变断裂寿命进行研究。建立不同成分镍基变形合金在不同温度下，外应力与蠕变断裂寿命之间关系模型，并进行网络训练，对合金的蠕变断裂寿命进行模拟。结果表明，模拟结果与实测结果符合良好，采用人工神经网络方法可以为镍基变形合金蠕变断裂寿命的预测提供一种有效的手段。     

基于多晶体塑性模型的纯铜轧制有限元模拟

以晶体塑性有限元理论为基础,在有限元软件ABAQUS中通过Voronoi图的多晶模型对不同初始取向的两种多晶纯铜试样轧制后的变形进行了分析.结果表明,轧制后多晶纯铜试样中晶粒自身的变形与其内部的应力、应变都不均匀,且与其取向、大小、形状及晶粒间的相互作用相关.     

大塑性变形过程中单晶和多晶铜的组织演变及变形机理研究

用等通道转角挤压(equal channel angular pressing,ECAP)法对单晶铜和多晶铜进行了多道次的挤压变形,对挤压过程中晶粒细化机理和变形机理进行了分析.结果表明,单晶铜和多晶铜在A路径下变形8道次以后,晶粒平均尺寸达到5 μm以下,但在4道次以后单晶铜沿挤压方向出现织构,多晶铜中出现均匀的等轴晶.TEM分析认为,晶粒位相差随剪切变形量的增加而增大,ECAP加工后材料内部大角度晶界数的增加导致了变形机制的改变,晶界滑移导致了晶粒转动趋势的增加.在多道次挤压后,单晶铜和多晶铜材料的微观结构特征是含有高密度位错的大角度晶界等轴晶组织,以及晶界上的非平衡结构.     

An Experimental Study on Laser Cutting Mechanisms of Polycrystalline Diamond Compacts

The objective of this study is to experimentally investigate the cutting mechanisms of polycrystalline diamond compacts (PDC) using two different lasers: (a) a near infrared Nd:YAG laser (Neodymium-doped Yttrium Aluminum Garnet) of 1064 nm wavelength and 100 μs pulse width; and (b) a green light KTP (Potassium Titanyl Phosphate)/Nd:YAG laser of 532 nm wavelength and 120 ns pulse width. To realize the objective, the study applies polishing, lapping and etching processes to the cut-surfaces of the PDC samples. It further observes and analyzes the processed cut-surfaces with scanning electron microscopy (SEM) and Raman spectroscopy. A discussion is provided to reveal the underlying physics of the laser cutting mechanisms, and a conclusion is drawn based on the outcomes from the experimental investigation and the discussion.     

基于人工神经网络的挤压变形抗力的建模

利用人工神经网络方法建立了挤压力系统模型，运用梯度下降法对BP神经网络进行训练，得到了15钢挤压时的挤压力与凹模锥角、凸模直径、断面缩减率的非线性映射关系。从而可预测在一定条件下挤压力的变化情况。结果表明：运用这种模型对挤压力进行预测是可行的。     

强烈塑性变形方法制备块体金属纳米材料

介绍了强烈塑性变形制备块体金属纳米材料的主要方法，分析了利用强烈塑性变形方法制备块体金属纳米材料的微观结构和性能。     

我国航空用变形钛合金材料

钛合金材料作为一种20世纪中叶出现并发展起来的新兴结构材料,因其具有优异的耐腐蚀性、高的比强度以及无磁性等一系列独特的优点,在航空航天等高端工业部门获得了广泛应用,目前飞机机体结构中的隔框、大梁、起落架以及航空发动机压气机匣、轮盘、叶片等承力部件大量使用钛合金材料制造。在上世纪60年代,美国、英国、前苏联等工业发达国家就已经在弋机及航空发动机制造中大量使用钛合金材料。我国钛合金材料在航空工业中的应用起步较晚,上世纪80年代开始才陆续在飞机及航空发动机制造中少量使用钛合金材料,但是进入21世纪之后,我国航空工业钛合金材料的应用水平大幅度提升。对我国目前已经进入工业化生产并在航空工业中获得工程化应用的变形钛合金材料进行了系统阐述。     

基于B/S模式的焊接材料数据库系统研究

结合企业用户需求,利用OracleDeveloperSuite中的FormsBuilder表单开发工具开发了一个基于浏览器/服务器(B/S)模式的焊接材料数据库系统。系统对焊接材料概述、物理及化学性能、力学性能及组织进行了信息化管理,实现了基于Web浏览器的焊接材料各项信息查询、浏览、添加和删除等功能。不仅为广大焊接工艺设计者提供了数据支持,同时实现了数据的统一化和集成化,使焊接材料数据在internet上得以共享。     

A New Model for Inverse Hall-Petch Relation of Nanocrystalline Materials

In the present article, a new model for inverse Hall-Petch relation in nanocrystalline materials has been proposed. It is assumed that lattice distortion along grain boundaries can cause internal stresses and high internal stresses along grain boundaries can promote the grain boundary yielding. The designed model was then verified using the nanocrystalline-copper data. The minimum grain size for inverse Hall-Petch relation is determined to be about 11 nm for Cu.     

工程材料微裂纹自愈合技术及其机理

综述了工程材料表面及内部微裂纹自愈合技术及其机理的研究现状和进展，并提出普通金属材料使用过程中所产生裂纹的愈合技术和机制研究应提到日程上。     

金属材料强化机理与模型综述

总结了金属材料强化的方法,分别为细晶强化、第二相强化、固溶强化和形变强化。其中,第二相强化又分为晶界强化和晶内强化。阐述了不同方法强化金属材料的机理,举例介绍了金属材料强化的效果,分析了金属材料强化的相关模型。     

A New Burr Formation Model for Orthogonal Cutting of Ductile Materials

This paper proposes a new model to predict the full formation of a burr in orthogonal cutting. The model is based on the theory of slip-lines, the equilibrium equation, and experimental observations of burr formation with relevant data gathered from previous studies. Unlike with existing models, the proposed model considers the influence of the deformation rate on burr formation as well as the compression factor of the exit surface during burr development. A Mathcad program was created based on the model. The program can visualize burr formation and can predict the geometrical characteristics of the burr. The results of visualization are presented in the paper. The influence of the tool rake angle, the workpiece angle and the undeformed chip thickness, on burr dimensions have been verified in experiments. The experimental results show that the model is suitable in the cutting of ductile materials.     

多晶硅薄膜的工艺研究

研究了制备性能优良非晶硅薄膜的工艺参数，对薄膜进行高温退火得到多晶硅薄膜。用X射线衍射仪(xRD)和扫描电镜(SEM)，观察薄膜的结晶情况以及晶粒的大小。结果表明：退火温度越高，退火时间越长，得到多晶硅薄膜的比例越高，晶粒也相对较大；薄膜在(111)方向上优先结晶，晶粒大小可以达到1μm，与理论值做了比较。     

时效过程中2124铝合金蠕变本构模型的研究

研究不同时效温度下2124铝合金蠕变性能及组织变化,建立合金的蠕变本构模型。结果表明,由于该模型采用了析出相瞬时体积分数增长率描述析出相变化,与试验结果更吻合,适合研究合金晶粒的非均匀形核长大。     

Investigation on the Creep Behavior of AZ91 Magnesium Alloy Processed by Severe Plastic Deformation

Metals and Materials International - This paper describes the grain refinement due to equal-channel angular pressing (ECAP) and the creep properties of the ECAP-processed AZ91 magnesium alloy. The...     

基于数学模型的M4高速钢热变形行为及组织演化分析

利用热模拟试验机对M4高速钢进行了热压缩变形,计算了其热变形激活能,构建了热变形本构方程,并对其组织演化进行了分析。结果表明,M4高速钢在热变形时具有明显的动态再结晶特征,温度及变形速率对流变应力和碳化物的形貌和分布影响显著。