奥氏体不锈钢丝激光焊接头的组织与力学性能

采用脉冲激光焊技术连接奥氏体不锈钢细丝.利用光学显微镜、扫描电镜等分析测试手段,研究了不锈钢丝激光焊接头的微观组织特点及激光焊参数对接头组织与力学性能的影响规律.结果表明,焊缝金属由奥氏体胞状晶和胞状树枝晶构成,热影响区主要为等轴晶,且过热区晶粒明显粗化.随着激光脉冲能量和脉冲宽度的增加,焊缝熔透率及熔宽增加,焊缝及热影响区组织有粗化的趋势.小的脉冲宽度(2,3ms)对于保证不锈钢丝焊接质量的稳定性是不利的.激光焊接头抗拉强度最大值为680MPa(脉冲宽度10ms,脉冲能量7.6J),焊缝中心区是焊接接头最薄弱的部位.     

异种铝合金电阻点焊接头的组织及性能

采用电阻点焊工艺对厚度为2 mm的5182铝合金和5754铝合金进行搭接焊,并使用金相显微镜观察其显微组织特点,使用拉伸试验机和维氏显微硬度仪测试焊接接头的力学性能。结果表明,焊接接头由3个典型区域组成：母材区、热影响区和熔核区;熔核区主要由边缘柱状晶和中心等轴晶组成,中心等轴晶区体积约占整个熔核区的90%。5182铝合金侧的热影响区出现较多大颗粒析出物,并出现液化裂纹,5754铝合金侧的热影响区无明显的析出物与液化裂纹产生。焊接接头的断裂形式为纽扣型断裂,均为 5754铝合金侧的熔核被剥离。熔核中柱状晶区硬度高于等轴晶区,位于两种铝合金侧的热影响区硬度均高于其对应的母材硬度。     

锌基合金激光焊焊接接头组织和性能的研究

通过金相显微镜、扫描电镜和能谱分析仪等分析手段,研究了锌基合金激光焊焊接接头的组织和性能。结果表明:锌基合金焊接接头熔合线明显,熔合区及热影响区很窄,组织比较均匀;焊缝中心位置的蒸发凹坑较明显。焊缝中心主要由等轴晶组成,焊缝中心与熔合线的中间区域主要由树枝状晶组成。熔合区及热影响区组织发生明显的重结晶,为细小的等轴晶,没有半熔化区晶粒组织及过热粗晶区组织出现。焊接接头的焊缝硬度最高,各区域的硬度分布为:焊缝热影响区、熔合区母材。     

AZ91D镁合金TIG焊接接头组织及性能研究

使用与母材AZ91D镁合金同质焊丝进行TIG焊接.采用金相显微镜、X射线衍射仪、拉伸试验机、布氏硬度计等分析测试手段对接头的组织特征、相组成和力学性能进行分析.结果表明:焊接电流为140 A,氩气流量12 L/min时,焊接接头的抗拉强度为母材的80%左右,断裂发生在热影响区.焊缝区组织是比母材晶粒细小、更均匀的等轴晶.X射线衍射表明该区由α-Mg固溶体和Mg17Al12相组成.     

镁合金交流和直流点焊接头组织分析

采用交流和直流两种方法对AZ31B镁合金进行了电阻点焊，分析了接头的组织形态。结果显示，焊点熔核中心为细小的等轴晶，结晶后的组织为非平衡凝固产生的远离平衡态的组织，在先共晶α-Mg相上析出β-Mg17Al12离异共晶体；直流点焊中加大电极压力使得焊点热影响区组织形态由等轴晶转换为树枝晶；交流点焊规范的改变不引起焊点组织形态的变化，只是影响析出相的数量。     

高频振动下的不锈钢激光焊接

在不锈钢激光焊接过程中对工件施加高频振动,研究不同焊接速度和振动频率对接头宏观成形、微观组织及显微硬度的影响. 结果表明,焊缝边缘为柱状树枝晶,中央为细小等轴晶,焊缝组织为奥氏体和残余δ铁素体. 焊接速度增加,虽可使熔宽和焊缝区晶粒尺寸减小,接头硬度增大,但无法阻碍树枝晶的生长. 施加高频振动可抑制枝晶的数量和大小,并增加焊缝中等轴晶的数量,优化接头综合性能. 振动频率增加,焊缝区晶粒尺寸减小、等轴晶数量增加且有细小等轴晶弥散分布于树枝晶之间,焊缝硬度增大,振动起到了细晶强化的效果. 而振动频率对熔宽并无明显影响.     

7055喷射成形高强铝合金激光焊接头组织及性能

采用激光焊接对2 mm厚喷射成形的7055-T76511铝合金进行焊接试验。通过显微硬度和拉伸试验测试焊接接头的力学性能,通过光学显微镜(OM)、扫描电镜(SEM)、背散射电子衍射技术(EBSD)以及X射线衍射(XRD)分析焊接接头的微观组织。结果表明,7055铝合金激光焊接头无明显的软化区,焊缝显微硬度最低,约为130~140 HV,接头的抗拉强度372 MPa,伸长率4.1%。焊缝组织有明显的三个区(热影响区、熔合区和焊缝区)。热影响区组织是产生了部分再结晶的等轴晶粒;熔合区由于非均匀形核形成了等轴非枝晶区(non-dendritic equiaxed grain zone,EQZ),晶粒尺寸3~8μm;焊缝区靠近熔合线为柱状枝晶,中心为胞状枝晶。     

ZK60镁合金薄板光纤激光焊接工艺

主要对厚度为2 mm的ZK60镁合金薄板进行光纤激光焊接工艺研究,分析研究了焊接接头各区域的显微组织和相组成,研究了激光焊焊接速度对ZK60镁合金焊接接头组织的影响规律。试验结果发现,ZK60镁合金焊接时采用适当焊接速度(1 200 mm/min≤v≤2 200 mm/min),焊接接头成形美观,焊缝鱼鳞纹均匀细密,无明显裂纹、咬边及焊瘤等表面缺陷,焊缝上表面有明显的下塌。在一定的激光功率(1 400 W)下,随着焊接速度的提高,熔池体积减小,焊缝的熔宽明显变窄,晶粒尺寸减小,熔合区晶粒的结晶形态变化趋势为胞状晶到树枝晶一直到等轴树枝晶;焊缝组织主要是α-Mg基体和呈连续网状分布于晶界上的Mg-Zn相,该相以颗粒状偏析于晶界。     

TC4钛合金激光焊接头微观组织和硬度

采用光学显微镜和场发射扫描电镜观察了TC4钛合金激光焊接接头的显微组织,测量了接头焊缝中心到母材的显微硬度。结果表明,母材由α相和其相界上断续分布的粒状β相组成。焊接接头组织由粗大等轴晶区、柱状晶区、细等轴晶区和热影响区过热组织组成。粗大等轴晶区组织形态有层片状α+β、魏氏体α和网篮状α+β3种,其显微硬度略低于柱状晶区和细等轴晶区,但比母材高;柱状晶区和细等轴晶区组织为针状马氏体,柱状晶区显微硬度相对较高。热影响区显微硬度与母材相差不大。     

轨道交通用6082铝合金焊接接头组织与性能

采用熔化极氩孤焊(MIG)方法,以ER5356焊丝作为填充材料,对轨道交通用6082铝合金进行焊接,并对获得的接头微观组织和力学性能进行分析测试.金相组织观察表明,接头焊缝金属区为细小的等轴晶组织,主要由α -Al基体相和Mg2Si强化相组成,而热影响区为树枝晶组织,晶粒有所长大.力学性能测试表明,接头的抗拉强度约为母...     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.