Effect of heat treatment on microstructures and properties of a novel Al-Zn-Mg-Cu alloy for oil drilling

In view of the special requirements for strength, heat resistance and corrosion resistance of Al-Zn-Mg-Cu alloy for oil drilling, the Al-6.2 Zn-2.5 Mg-1.6 Cu alloy was prepared by increasing Cu content on basis of Russian Series 1953 alloy. The effect of heat treatment on the microstructures and properties of the alloy was characterized by optical microscope(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM), and investigated by tensile test at room temperature, thermal exposure test and corrosion test. The results show that the strength after T6 aging treatment exhibit a decrease trend as an increase of the solution temperature from465 °C to 480 °C. After the solution treated by the rate of 470 °C/1 h, second phases dissolve into the matrix very well and the strength property reaches optimum. The alloy has better comprehensive properties treated by a solution treatment of 470 °C/1 h and then followed by an aging treatment of 120 °C/24 h + 170 °C/1 h + 120 °C/24 h. Under the aging state, the precipitated phases inside the grains are suitable in size, while on the grain boundary distribute discontinuously and the precipitate-free zone is obvious. Besides, the alloy still maintain high tensile properties. The yield strength, tensile strength and elongation are 650 MPa, 686 MPa,12.0%, respectively. The yield strength retention after heat exposure is 92%. The alloy has good corrosion resistance and the exfoliation corrosion degree. The average corrosion rate in the H_2S and CO_2 environment is 0.0024 mm/a, which is far less than the required 0.12 mm/a. It is insensitive to H_2S and CO_2 environments.     

南方丝绸之路对大理的影响及当前的对策

大理历史悠久,文化灿烂,风光秀丽,古道纵横。过去南方丝绸之路对大理的经济、政治、交通、文化、宗教等有较大的影响,今天在国家"一带一路"的大战略背景下,大理应该怎么办,大理学院应该怎么办,这是当代学人的新课题。以古代南方丝绸之路为出发点,建议今天大理的"一带一路"定位为交往之路、人情之路。     

物理学与美学

探索物理学中美的因素,领悟自然科学之美,激发科学创新精神。     

对摩擦力作功与摩擦生热的量度的认识

本文通过对摩擦力作功与不擦生热的讨论，给出摩擦生热的量度方法．     

原子结构中的物理理论

本文较系统地介绍了有关原子结构方面的一些基础理论,由定性到定量,并应用量子力学知识描绘了原子结构状态。     

新型三曲线机构与卡西尼卵形线

本文论述了由作者发明的可绘制双纽线、纺锤线及椭圆三种曲线的新型机构的构成特点;形成这三类曲线族机构连杆上浮动点的轨迹方程式及各类曲线形成的参数 l_6(=l_5)的域值;以及与标准椭圆和卡西尼卵形线的比较。     

PB在企业管理系统中与多种数据库的连接

分析了使用面向对象数据库软件Power Builder开发煤气公司一表一卡管理系统过程中，对SQL Server和Visual Foxpro两种不同数据库的连接，提出了解决新系统与旧系统的数据兼容问题。     

一类双曲方程反问题的存在性和唯一性

讨论了如何确定下述双曲方程中反问题中的未知系数ｑ（ｘ），用压缩映像原理证明了反问题的存在性和唯一性定理。     

PDE-Based Medial Axis Extraction and Shape Manipulation of Arbitrary Meshes

Shape skeletonization （i.e., medial axis extraction） is powerful in many visual computing applications, such as pattern recognition, object segmentation, registration, and animation. In this paper, the authors expand the use of diffusion equations combined with distance field information to approximate medial axes of arbitrary 3D differential properties. It offers an alternative solids represented by polygonal meshes based on their but natural way for medial axis extraction for commonly used 3D polygonal models. By solving the PDE along time axis, this system can not only quickly extract diffusion-based medial axes of input meshes, but also allow users to visualize the extraction process at each time step. In addition, the proposed model provides users a set of manipulation toolkits to sculpt extracted medial axes, then use diffusion-based techniques to recover corresponding deformed shapes according to the original input datasets. This skeleton-based shape manipulation offers a fast and easy way for animation and deformation of complicated mesh objects.     

双门电冰箱的热传导问题

本文将根据热传导方程,对电冰箱达定态过程进行理论推导,以及定态后电冰箱单位时间吸收的热量,并由此计算出由于冰箱箱体的热量泄漏而消耗的能量。