Determination of parent orientation maps in advanced titanium-based alloys

In the past few years, reconstruction methods have been developed and applied successfully to restore the β microtexture in titanium alloys. This contribution shows how these methods are extended to other transformations often encountered in advanced titanium alloys: the α (hcp)→γ (tetragonal) and the β (bcc)→O (orthorhombic) transformation. The efficiency of the restitution depends on specific crystallographic features of the investigated phase transformations. Therefore, the paper outlines these crystallographic specificities for some advanced titanium alloys. To illustrate the capability of the method to reconstruct the parent phase, different restored parent microtextures of these alloys are presented. The results show that the reconstruction methods are an efficient tool to study the microstructure and texture modifications induced by these phase transformations.     

一种光学元件面形三维重建的算法研究

为了在线检测光学元件面形,介绍一种基于线结构光扫描测量和立体视觉测量相结合的三维检测方法,目前这种方法多用于检测高反射率的物体,因此将该方法运用于检测光学元件面形是一种新的尝试。实验的三维重建算法是通过MATLAB和VC++软件共同编写程序实现的,实验结果表明,将这种方法运用于检测光学元件是可以真实还原光学元件三维外貌特性的,所以它的研究具有可行性和研究价值。     

Fretting damage assessment of titanium alloys using orientation imaging microscopy

The formation of fretting damage and cracks depends strongly on the microstructure. Recent advances in orientation imaging microscopy (OIM) make it possible to obtain new assessment measurements of the near-surface layers containing fretting damage. In particular, crystallographic grain orientation, misorientations between grains, accumulation of plastic deformation, and the evolution of microstructure leading to microtexture formation and twinning can be determined using OIM. Insight into the hexagonal close packed (HCP) structured metals and alloys is the focus of this study. The examination of the subsurface layers of Ti–6Al–4 V samples reveals that OIM using electron backscatter diffraction (EBSD) is a useful tool to quantify evolution of strain-induced microstructural changes due to deformation in the near-surface layers both in surface treatment processes and in fretting or sliding conditions. Fretting damage in a commercially pure titanium (CP Ti) and a near α Ti–5Al–2.5Sn is also assessed to further evaluate this new characterization method. This study summarizes what can be gained from OIM and the challenges associated with using the technique to characterize near surface microstructures.     

Three-dimensional EBSD study on the relationship between triple junctions and columnar grains in electrodeposited Co–Ni films

Electrodeposited nanocrystalline materials are expected to have a homogeneous grain size and a narrow grain size distribution. In Co–Ni electrodeposited films, however, under certain conditions an undesired columnar grain structure is formed. Fully automated three‐dimensional (3D) orientation microscopy, consisting of a combination of precise material removal by focussed ion beam and subsequent electron backscatter diffraction (EBSD) analysis, was applied to fully characterize the grain boundaries of these columnar grains in order to gain further understanding on their formation mechanisms. Two‐dimensional orientation microscopy on these films indicated that the development of columnar grains could be related to the formation of low‐energy triple junctions. 3D EBSD allowed us to verify this suggestion and to determine the boundary planes of these triples. The triplets are formed by grain boundaries of different quality, a coherent twin on the {} plane, an incoherent twin and a large‐angle grain boundary. These three boundaries are related to each other by a rotation about the 〈〉 direction. A second particularity of the columnar grains is the occurrence of characteristic orientation gradients created by regular defects in the grain. Transmission electron microscopy was applied to investigate the character of the defects. For this purpose, a sample was prepared with the focussed ion beam from the last slice of the 3D EBSD investigation. From the TEM and 3D EBSD observations, a growth mechanism of the columnar grains is proposed.     

序列图像的三维重构方法

依据光学显微镜的多幅序列图像,通过比较多个层面上的图像,并根据光学显微镜的成像特性设计一种实体重构方法,完成三维图像的重建显示分析技术研究。提出以软件处理技术实现对多幅断层图像进行三维重建分析,较好地实现通过解卷积去除离焦平面的模糊图像,进而对多幅序列图像进行三维重建分析,得到物体表面的完整造型。     

基于Matlab的一维插值在曲面三维重建中的应用

提出了基于Matlab的任意闭合型值点的一维三次样条插值方法,并应用于闭曲面的三维重建中。首先对物体进行360°扫描测量,获得物体表面三维条形图。经过曲面切片、型值点提取、点列排序、一维插值、数据融合,得到闭曲面四边形网格图。给出了完整的基于Matlab的算法描述,并通过三维重建实例,验证了方法的有效性和可行性。     

钛合金材料的切削加工

钛合金材料的切削加工,历年是从事机械制造的技术人员感兴趣的问题。笔者根据多年的实践,整理出一套实用的加工方法。本文得出的结论及实际数据可供钛合金材料的切削加工部门参考。     

Effect of annealing temperatures on the secondary re-crystallization of extruded PM2000 steel bar

The ferritic oxide dispersion-strengthened alloy PM2000 is an ideal candidate for high-temperature applications as it contains uniform nano-oxide dispersoids, which act as pinning points to obstruct dislocation and grain boundary motion and therefore impart excellent creep resistance. The development of the microstructure during re-crystallization of oxide dispersion-strengthened alloys has been discussed by a number of authors, but the precise mechanism of secondary re-crystallization still remains uncertain. Hence, this work is aimed at investigating the re-crystallization behaviour of extruded PM2000 bar for different annealing temperatures, using electron backscatter diffraction, in particular, to determine grain orientations, grain boundary misorientation angles, etc. The results show that the as-extruded bar microstructure comprises both low-angle grain boundaries pinned by oxide particles and high-angle boundaries that will have inherent boundary mobility to allow boundary migration. In addition, dynamical re-crystallization was found in the outer region of the non–heat-treated PM2000 bar, which suggested that deformation heterogeneities can be introduced during thermo-mechanical processing that enhance the nucleation of re-crystallization. Subsequent heat treatments promote and stimulate secondary re-crystallization, giving rise to large grains with few sub-grain boundaries.     

ICT和RP＆M在CAD／CAM中的应用

介绍了ＩＣＴ（ＩｎｄｕｓｔｒｉａｌＣｏｍｐｕｔｅｄＴｏｍｏｇｒａｐｈｙ）和ＲＰ＆Ｍ（ＲａｐｉｄＰｒｏｔｏｔｙｐｉｎｇａｎｄＭａｎｕｆａｃｔｕｒｉｎｇ）这两项当今引人注目的高新技术，探讨了在ＣＡＤ／ＣＡＭ领域的应用途径、发展前景和重要意义，并对相关的一个重要算法，即基于ＩＣＴ切片的三维几何模型重建，进行了归纳阐述。     

Simple 3D images from fossil and Recent micromaterial using light microscopy

We present a technique for extracting 3D information from small-scale fossil and Recent material and give a summary of other contemporary techniques for 3D methods of investigation. The only hardware needed for the here-presented technique is a microscope that can perform dark field and/or differential interference contrast with a mounted digital camera and a computer. Serial images are taken while the focus is successively shifted from the uppermost end of the specimen to the lowermost end, resulting in about 200 photographs. The data are then processed almost completely automatically by successive use of three freely available programs. Firstly, the stack of images is aligned by the use of CombineZM , which is used to produce a combined image with a high depth of field. Secondly, the aligned images are cropped and sharp edges extracted with the aid of ImageJ . Thirdly, although ImageJ is also capable of producing 3D representations, we preferred to process the image stack further using osirix as it has the facility to export various formats. One of the interesting export formats is a virtual Quicktime movie file (QTVR), which can be used for documentation, and stereo images can also be produced from this Quicktime VR. This method is easy to apply and can be used for documenting specimens in 3D (at least some aspects) without having to prepare them. Therefore, it is particularly useful as a safe method for documenting limited material, before using methods that may destroy the specimen of interest, or to investigate type material that cannot be treated with any preparatory technique. As light microscopes are available in most labs and free computer programs are easily accessible, this method can be readily applied.     

MICRO-ROBOT FOR MEASUREMENT AND THREE-DIMENSION RECONSTRUCTION OF MICROPIPES

0 INTRODUCTIONPipes or hollow bodies in petrolic industry, natural gas indus-try, chemical industry, energy sources, nuclear energy industry,automobile and aeronautic industry etc, are charged with liquidtransmission. Especially for the liquid in high pre…     

用立体视觉测量多自由度机械装置姿态的研究

提出一种立体视觉测量多自由度机械装置姿态的方法。方法的摄像中所含的参数物理意义明显,考虑了镜头的畸变,并运用最小二乘法拟合这些参数。实验结果表明,这种测量方法具有较高的精度。     

三维扫描技术在大型钛合金件余量检测的应用研究

针对大型3D打印钛合金件加工余量检测、协调困难的技术问题,采用新的三维扫描技术准确地对毛坯进行了扫描对比,得到了其余量分布结果,并根据余量分布结果实现了对毛坯的粗加工余量协调,高效地解决毛坯余量差异大、局部余量较小的余量协调问题,为不规则、大型结构件的余量检测分析提供了重要技术支持。     

基于Pro／E的牙列快速原型制造

探讨了Pro/E的牙列快速原型制造过程中的一些关键技术及其医学应用。