Microstructure,mechanical properties and wear resistance of an Al–Mg–Si alloy produced by equal channel angular pressing

Microstructure, mechanical properties and wear resistance in an ultrafine-grained Al–Mg–Si alloy fabricated utilizing a combination of equal channel angular pressing (ECAP) and dynamic aging were investigated in this paper. The results indicated that the grain size of the ECAP alloy was significantly refined, i.e., to ~239 nm after three ECAP passes. Meanwhile, the yield and tensile strength of the ECAPed material reached 340 MPa and 445 MPa, respectively, while maintaining a significant uniform elongation of 14%. Wear resistance results demonstrated that the wear rate, wear depth and width of the ECAPed material decreased in comparison with the solution-treated (SST) and peak-aged (T6) conditions under a load range of 5–25 N. The adhesive wear that occurs in the undeformed specimens at 10 N does not appear in the ECAPed specimen at the same load, indicating that the ECAPed specimen delay the appearance of more serious wear mechanisms under certain loads. The cooperative interaction of high density nano-scale β" precipitates and dislocations resulted in a combination of super-high strength and good work hardening ability which suppressed the extension of cracks between the friction layer and the plastic deformation zone. As a consequence, the combination of ECAP and dynamic aging brings a significant improvement for antifriction performance of the 6061 aluminum alloy.     

高速、多幅、傅里叶频谱存贮型动态全息干涉术实验成功

我系研究了一种基于傅里叶频谱存贮原理的二次曝光新技术。采用脉宽和间隔可调的调制脉冲对激光光源即可对瞬态流场进行高速,多幅、动态全息干涉摄影。     

动力学规律性与统计规律性

本文阐明了动力学规律性和统计规律性的特点,以及二者之间的关系。     

动力减振实验装置的结构设计与研制

介绍动力减振实验装置的结构、实验的方法、步验与数据处理。实验结果表明所采用的设计方法是合理的、可行的。     

半环式传感型骨外固定器的力学特性实验

通过对尸胫骨 -传感器骨外固定器系统的动、静刚度及应力遮挡率进行了实验研究 ,表明半环四针传感型骨外固定器较两针型的刚度大 ,因此在骨愈合初期、粉碎性骨折宜采用四针结构 ,以避免错位、成角 ;愈合中后期用两针结构 ,以减小应力遮挡     

试谈动态思维训练

在物理量相互制约的物理习题中,有一类A量取得特殊值,B量取极值问题。可称“条件极值题”。本文探讨了用《高中物理客观性命题研究》中习题训练动态思维。     

人类对地球形状认识的辩证过程

在系统讨论了人类对地球形状认识的复杂历史之后,作者认为这是一个“否定之否定”式的螺旋状上升过程,即“非球→球→非球…”的过程。在经历了5次“非球→球”的认识反复之后,目前人类已跨入对地球本身便存在着“球(?)非球”的动态变化过程的认识这个崭新的阶段。     

co—H空间上自同伦等价群的若干结果

研究有关co H 空间上的自同伦等价.当co H 空间X是1 连通的有限CW 复形时,εSP(SX)是有限生成的群.另外本文还得到εco H(X)是有限群的一个充分条件.     

1次+3次平面多项式系统的代数分类

采用代数不变式和空间直和的理论,对1次 3次平面多项式系统在保证轨线走向不变的前提下进行代数分类,共分成40个等价类.     

基于时效性的垂直搜索及其应用

基于时效性信息的特征,构建了一个用来提高专业搜索的"查全、准、新率"的垂直搜索引擎. 以航空机票价格为例,分析了时效性信息的获取和过滤技术,并给出了基于时效性垂直搜索引擎的关键程序.