镁合金搅拌摩擦焊接组织特征研究

通过对镁合金AZ31进行搅拌摩擦焊获得了成型良好的焊缝,采用金相显微镜对焊缝组织进行了分析,并采用透射电镜和X射线能谱仪对晶粒形貌和晶界析出的第二相进行了观测分析。结果表明,镁合金搅拌摩擦焊可以获得组织致密的焊缝,焊缝区域根据组织特点可以分为焊核区、热机影响区和热影响区;焊核区"洋葱环"之间呈现层片状结构,晶界强化相数量减少且尺寸变小;热机影响区在前进侧和焊核区有明显的分界,晶粒呈细长条状,后退侧和焊核区分界相对不明显,晶粒变形较小;热影响区在前进侧较窄,组织与母材组织相比变化较小,而后退侧热影响区较宽,晶粒尺寸有所增长,这与搅拌摩擦过程中金属切削迁移的堆积过程有关。     

2060搅拌摩擦焊对接接头显微组织与析出相分析

选用Al-Li-Cu-Mg系铝锂合金2060,开展搅拌摩擦焊对接接头显微组织与析出相演变规律研究.搅拌摩擦焊对接接头,呈现典型的母材、热影响区、热机影响区和焊核区四区分布特点.母材为双向板条组织,在α板条中有大量三角形AlCu2Mn化合物析出,但在其它相区,当受到热影响时,该相消失;热影响区组织粗大,热机影响区晶粒受到机械力作用,前进侧拉长,后退侧破碎;焊核区为等轴晶组织,出现了高温析出相AlxCuxMn,均布于整个焊核区域.接头显微硬度在母材区最高,热影响区最低,焊核区低于母材,稳定在115 HV.     

2060搅拌摩擦焊对接接头显微组织与析出相分析

本文选用Al-Li-Cu-Mg系铝锂合金2060,开展搅拌摩擦焊对接接头显微组织与析出相演变规律研究.搅拌摩擦焊对接接头,呈现典型的母材、热影响区、热机影响区和焊核区四区分布特点.母材为双向板条组织,在α板条中有大量三角形AlCu2Mn化合物析出,但在其它相区,当受到热影响时,该相消失;热影响区组织粗大,热机影响区晶粒受到机械力作用,前进侧拉长,后退侧破碎;焊核区为等轴晶组织,出现了高温析出相AlxCuxMn,均布于整个焊核区域.接头显微硬度在母材区最高,热影响区最低,焊核区低于母材,稳定在115 HV.     

铝锂合金搅拌摩擦焊研究

采用柱形带螺纹搅拌针搅拌摩擦焊接5 mm厚铝锂合金轧制板材,并对接头组织、力学性能及断裂特性进行了研究.接头形成差别明显的三个区域:焊核区、热机影响区和热影响区.拉伸实验表明,接头强度随着焊接速度的提高先增加,并于v=60mm/min处达到最大值340MPa;当v＞60mm/min时,接头强度迅速下降.铝锂合金搅拌摩擦接头断裂模式为韧脆混合型断裂,并以脆性断裂为主.     

铝合金厚板静止轴肩搅拌摩擦焊接头组织及性能

采用8.5 mm厚度2A14-T4铝合金和自主研制搅拌工具进行静止轴肩搅拌摩擦焊（stationary shoulder friction stir welding,SSFSW）实验,探讨焊接工艺参数对接头组织和力学性能的影响规律。结果表明：只有在低转速工艺参数范围内（转速ω=400~600 r/min与焊接速率v=60~120 mm/min）可获得焊缝表面光滑、无缺陷厚板铝合金SSFSW焊接接头。SSFSW焊缝区主要由焊核区（NZ）组成,周围热力影响区（TMAZ）及热影响区（HAZ）宽度明显减小,焊核区与搅拌针形状类似且由两种不同尺寸细小等轴晶构成,前进侧NZ晶粒比后退侧NZ更为细小。接头显微硬度呈"W"状分布,NZ硬度值可达到母材硬度80%~90%,TMAZ与HAZ交界处存在软化区,硬度最低为母材硬度72%左右。在给定ω=500 r/min,v=140 mm/min焊接参数下,SSFSW接头抗拉强度可达到母材的88%,断裂位置多位于后退侧TMAZ与HAZ交界处软化区,具有韧性断裂特征。     

厚板铝合金搅拌摩擦焊接头的冲击性能

采用搅拌摩擦焊对厚度为30 mm的2A12铝合金板材进行对焊连接,分析了接头不同厚度处的微观组织与冲击性能。结果表明:随着热输入量的减少,接头上层的晶粒相比于下层出现了粗化现象,导致接头上层区域的冲击韧性低于下层。焊核区晶粒最为细小,热机影响区次之,热影响区晶粒最为粗大;焊核区的冲击韧性高于热影响区,热机影响区由于存在微型裂纹,所以冲击韧性最低。焊核区上层的晶粒尺寸小于热机影响区下层的晶粒尺寸,但焊核区上层的冲击韧性低于热机影响区下层的冲击韧性,这是由于焊核区所含的Al₂CuMg脆性第二相的数量较多。焊接接头冲击韧性的变化不仅与焊缝不同区域的微观组织变化有关,还与该区域的第二相数量有关。     

LC52厚板搅拌摩擦焊组织性能分析

采用搅拌摩擦焊方法对厚度为15mm的LC52铝合金板进行了单道焊接试验,并对焊缝的微观组织与力学性能进行了分析.试验结果表明,在旋转速度为1500r/min,且焊接速度为60mm/min时,可以获得较好的焊缝组织,其抗拉强度达到了338MPa.焊核区内是细小均匀的等轴晶,平均晶粒大小在4μm左右.焊缝两侧热机影响区的组织存在较大差异,前进侧热机影响区为塑性变形角较小的窄条形组织,后退侧热机影响区为塑性变形角较大的扁平块状组织.热影响区的组织发生了粗化.焊缝中的部分强化相η'相因过时效转变为η相是焊缝强度低于基材强度的主要原因.     

搅拌头转速对YL113压铸铝合金FSW接头组织性能的影响

对4 mm厚的压铸态YL113铝合金进行了搅拌摩擦焊工艺试验研究,采用OM、SEM/EDS、XRD、万能拉伸试验机等分析研究了搅拌头转速对接头的微观组织和力学性能的影响。结果表明,当焊接速度为40 mm/min时,搅拌头转速在700~1 500 r/min范围内均可获得成形良好、无外观缺陷的焊缝,焊缝截面呈倒梯形,前进侧有明显分界线,而后退侧分界线模糊。热影响区保持铸态的枝晶形貌,但晶粒有一定程度的长大。热机影响区组织呈带状并遗传了母材组织的孔洞缺陷,其中前进侧的孔洞呈纤维状,其数量和尺寸随搅拌头转速增加而增加;后退侧除转速700 r/min时出现类裂纹状缺陷外,其余转速均有大尺寸孔洞缺陷出现,且数量和尺寸随搅拌头转速增加而增加。焊核区为典型变形组织,Si和其他第二相均呈细小颗粒状弥散分布。随搅拌头转速增加,焊接接头抗拉强度和伸长率均呈先增后减的规律,搅拌头转速为900 r/min时,抗拉强度和伸长率均达到最大值。     

压铸态AZ91D镁合金搅拌摩擦焊接头微观组织研究

采用搅拌摩擦焊工艺对4mm厚的压铸态AZ91D镁合金进行对接工艺实验,搅拌头旋转速率1500r/min,焊接速率120mm/min;使用光学显微镜和扫描电镜对焊接接头微观组织进行了研究。结果表明:焊缝外观成形美观,但内部存在贯穿型隧道状孔洞缺陷;焊核区为典型的变形-再结晶组织,为细小、均匀的等轴晶;机械-热影响区为变形-部分再结晶组织,热影响区组织形貌与母材相近但伴有轻微的长大现象;焊核区与机械-热影响区的过渡具有以下特征:在前进侧呈现"突变"特征,在后退侧呈现"渐变"特征。     

6005A-T6铝合金搅拌摩擦焊接头组织与力学性能特征

采用光学显微镜、扫描电子显微镜、透射电子显微镜、拉伸实验机和显微硬度计对6005A铝合金搅拌摩擦焊接头的微观组织及力学性能进行了研究。结果表明:焊核区为细小的等轴晶,几乎所有粒子溶于基体;热机械影响区呈现为被拉长的畸变晶粒,且存在大量的位错;热影响区的组织明显粗化,处于过时效状态。与母材相比,搅拌摩擦焊接头的强度及伸长率均有下降趋势,且接头出现软化,最小硬度值出现在前进侧的热影响区内。搅拌头旋转速率为1200r/min、焊接速率为200mm/min时可获得优质接头,抗拉强度达到母材强度的72%,伸长率达到母材的69%。     

凝固科学技术与材料

从凝固科学与实践发展的角度介绍了当前凝固材料体系的基本框架和凝固科学主要发展阶段的基本理论。作为材料科学与工程的基本组成，凝固科学技术正在现代科学理论的基础上针对传统材料的改性提高和新材料的发展需求，以控形、控构、控性为目标开展优质铸件的定向、晶体生长、快凝、深过冷及各种新型和超常领域凝固过程的研究，并介绍了其中某些方面和展望了可能的发展趋势。     

Development and challenges of planning and scheduling for petroleum and petrochemical production

Production planning and scheduling are becoming the core of production management, which support the decision of a petrochemical company. The optimization of production planning and scheduling is attempted by every refinery because it gains additional profit and stabilizes the daily production. The optimization problem considered in industry and academic research is of different levels of realism and complexity, thus increasing the gap. Operation research with mathematical programming is a conventional approach used to address the planning and scheduling problem. Additionally, modeling the processes, objectives, and constraints and developing the optimization algorithms are significant for industry and research. This paper introduces the perspective of production planning and scheduling from the development viewpoint.     

江澳两地高校文创设计的协同研究与商业实践

目的 探索江门世遗文化的传承、发展和转化的新思路,践行国家在《粤港澳大湾区发展规划》纲要中要求江门承担与港澳地区文化创意合作与开发任务的分工。方法 与澳门高校紧密合作,开展专业培训课程,以开平碉楼为例,从人文视角开展设计研究,梳理开平碉楼的文化脉络,把世遗文化的元素和其背后的文化融入文创产品中,提升文创产品的附加值,推动当地文创产业结构的变革。结果 两地高校构建了稳定的科研团队,开设长期有效的设计培训课程,与景区建立了研究协作关系,帮助景区构建了一套产销研的商业模式。结论 以跨区域高校合作为平台,以文创产品为抓手,依托江澳两地的资源优势,可以构建江门世遗文化全新的品牌形象,最终推动开平世遗文化的活化。     

Error and uncertainty in modeling and simulation

This article develops a general framework for identifying error and uncertainty in computational simulations that deal with the numerical solution of a set of partial differential equations (PDEs). A comprehensive, new view of the general phases of modeling and simulation is proposed, consisting of the following phases: conceptual modeling of the physical system, mathematical modeling of the conceptual model, discretization and algorithm selection for the mathematical model, computer programming of the discrete model, numerical solution of the computer program model, and representation of the numerical solution. Our view incorporates the modeling and simulation phases that are recognized in the systems engineering and operations research communities, but it adds phases that are specific to the numerical solution of PDEs. In each of these phases, general sources of uncertainty, both aleatory and epistemic, and error are identified. Our general framework is applicable to any numerical discretization procedure for solving ODEs or PDEs. To demonstrate this framework, we describe a system-level example: the flight of an unguided, rocket-boosted, aircraft-launched missile. This example is discussed in detail at each of the six phases of modeling and simulation. Two alternative models of the flight dynamics are considered, along with aleatory uncertainty of the initial mass of the missile and epistemic uncertainty in the thrust of the rocket motor. We also investigate the interaction of modeling uncertainties and numerical integration error in the solution of the ordinary differential equations for the flight dynamics.     

Density and viscosity of tetralin and trans-decalin

New measurements are reported for the density and viscosity of tetralin and trans-decalin. The density was determined from room temperature to 60°C for tetralin and to 95°C for trans-decalin. The kinematic viscosity was measured up to temperatures slightly above 100°C. Our results improve upon the values recommended by the American Petroleum Institute for these liquids.     

Creation and motion of dislocations and fracture in metal and silicon crystals

By making a step on one surface ( ) of a rectangular small paralellepiped copper crystal, dislocations could be created by the molecular dynamic method. The dislocation created was not a complete edge dislocation but a pair of Heidenreich-Shockley partial dislocations. Each time a dislocation was created, the stress on the surface was released. Small copper crystals having a notch were pulled (until fracture), compressed and buckled by use of the molecular dynamic method. An embedded atom potential was used to represent the interaction between atoms. Dislocations were created near the tip of the notch. A very sharp yield stress was observed. The results of high speed deformations of pure silicon small crystals using the molecular dynamics are presented. The results suggest that plastic deformation may be possible for the silicon with a high speed deformation even at room temperature. Another small size single crystal, the same size and the same surfaces, was compressed using molecular dynamic method. The surfaces are {110}, {112} and {111}. The compressed direction was [111]. It was found that silicon crystals are possible to be compressed with a high speed deformation. This may suggest that silicon may be plastically deformed with high speed deformation.     

SMC／BMC的回收与再利用

SMC／BMC废弃物对工业及环境造成了很大影响，指出了SMC／BMC回收再利用的紧迫性。通过对目前国际上SMC／BMC回收再利用的3种典型途径优缺点的对比，参照国外SMC／BMC回收再利用的先进方法，对我国SMC／BMC回收再利用提供了可行的建议．     

The Candela and Photometric and Radiometric Measurements

The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements.