新型镁合金大变形技术的研究与验证

研究了一种正挤压与等通道挤压相结合的新的Extrusion-Shearing(ES)变形方法。应用有限元法对ES变形过程进行了计算机模拟,表明ES技术可以大大提高累积应变和动态再结晶晶粒的体积分数。在Gleeble1500热模拟机上安装ES成形模具,对ES成形挤出的棒料进行微观组织观察,并对热模拟的数据进行处理。结果表明,ES成形可以细化晶粒并提高成形的均匀性。计算机模拟和热模拟实验表明,ES成形是一种新型的镁合金大塑性变形方法,可以有效细化晶粒、提高组织的均匀性     

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用斯太尔摩控制冷却轧制工艺生产的高碳索氏体盘条,其金相组织与其他工艺轧制的盘条(如热轧盘条)有显著的不同,为能准确地测量高碳索氏体盘条中的索氏体百分含量,以金属学与扩散相变理论为基础,深入研究了索氏体盘条金相组织的特殊性及各种组织的形态特征,按照组织的形态特征,将索氏体盘条中的组织划分成片状珠光体(粗珠光体)、层状索氏体(细珠光体)、珠光体索氏体过渡态组织(PS组织)及非索氏体组织4类.将过渡态组织划分成4种形式,给出了将过渡态组织划分为珠光体和索氏体的基本原则.     

Ti_(45)Cu_(35)Zr_8Ni_7Pd_5块体非晶合金的形成能力及力学性能(英文)

利用铜模铸造方法制备了Ti45Cu35Zr8Ni7Pd5合金圆棒。通过XRD、SEM和DSC等手段研究了合金的组织,讨论了合金的玻璃形成能力,测定了合金的力学性能。结果表明,直径为2mm的圆棒为单一金属玻璃相,3mm和4mm直径的圆棒由金属玻璃相和TiCu结晶相组成。直径为2mm的圆棒具有最高的压缩断裂强度(2160MPa)和最高的硬度(维氏硬度,5600MPa)。压缩强度和硬度随着圆棒直径的增加而降低,但变形能力增加。     

Si的添加对Zr-Fe-Ou合金系统的组织和力学性能的影响

在Zr-Fe—Cu合金中添加Si,利用铜模铸造法制备出直径为3mm的Zr基非晶／晶体复合材料。采用X射线衍射（XRD）、扫描电子显微镜（SEM）和微机控制电子式万能试验机等技术手段,研究了Si元素的添加对Zr-Fe-Cu合金的微观结构、非晶形成能力、压缩力学性能以及断口形貌的影响。结果表明：Si元素对非晶材料的性能与结构有很大的影响,能够提高合金的强度和塑性。     

冷镦钢线材质量异议原因分析

分析了马钢低碳冷镦钢系列、自攻螺钉系列、中碳冷镦钢系列、免退火系列、超细晶粒非调质钢线材质量异议的主要原因,即表面裂纹、折叠、划伤引发了表面开裂,成分偏析、组织结构异常及非金属夹杂物导致性能不均匀,热处理工艺及冷成型工艺不当造成加工缺陷,据此提出了相应的改进措施,使质量异议比例下降65%以上.     

桑塔纳轿车油门操纵杆断裂分析

应用组织分析和断口分析方法揭示桑塔纳轿车油门操纵杆冲压弯曲成型过程中发生断裂的原因。并采用有限元方法对冲压成型过程进行应力模拟。     

Fabrication of fine-grained,high strength and toughness Mg alloy by extrusion−shearing process

A novel extrusion?shearing (ES) composite process was designed to fabricate fine-grained, high strength and tough magnesium alloy. The structural parameters of an ES die were optimized by conducting an orthogonal simulation experiment using finite element software Deform-3D, and Mg?3Zn?0.6Ca?0.6Zr (ZXK310) alloy was processed using the ES die. The results show that the optimized structural parameters of ES die are extrusion angle (α) of 90°, extrusion section height (h) of 15 mm and inner fillet radius (r) of 10 mm. After ES at an extrusion temperature and a die temperature of 350 °C, ZXK310 alloy exhibited good ES forming ability, and obvious dynamic recrystallization occurred in the forming area. The grain size decreased from 1.42 μm of extrusion area to 0.85 μm of the forming area. Owing to the pinning of second phase and formation of ultrafine grains, the tensile strength, yield strength and elongation of alloy reached 362 MPa, 289 MPa and 21.7%, respectively.     

35MnVS非调质钢连杆应用研究

通过对非调质钢35MnVS和调质钢55钢在生产轿车连杆进行的金相组织、结构、性能等方面的对比,说明用35MnVS生产汽车连杆具有较好的性能和经济效益。     

Effects of deformation parameters on microstructure and mechanical properties of magnesium alloy AZ31B

Plastic deformation and dynamic recrystallization (DRX) behaviors of magnesium alloy AZ31B during thermal compression and extrusion processes were studied.In addition, effects of deformation temperature and rates on the microstructure and mechanical properties were investigated.The results show that the DRX grains nucleate initially at the primary grain boundaries and the twin boundaries, and the twinning plays an important role in the grain refinement.The DRX grain size depends on the deformation temperature and strain rate The average grain size is only 1 μm when the strain rate is 5 s-1 and temperature is 250 ℃.It is also found that the DRX grain can grow up quickly at the elevated temperature.The microstructure of extruded rods was consisted of tiny equal-axis DRX grains and some elongated grains.The rods extruded slowly have tiny grains and exhibit good mechanical properties.     

Microstructural evolution during RAP process and deformation behavior of semi-solid SKD61 tool steel

Semi-solid forming technology has several advantages over the conventional metal forming process owing to the unique behavior and characteristic microstructure of metals in the semi-solid state. With the aim of establishing a shorter process chain for manufacturing the high-quality tools required for forming, the microstructural evolution and basic deformation mechanism of the hot-working tool steel SKD61 in the semi-solid-state were studied experimentally. The feasibility of the recrystallization and partial melting (RAP) process for the fabrication of SKD61 stock with a uniform spherical microstructure was validated. The effects of parameters in RAP processing, such as the predeformation temperature and predeformation ratio, on grain refinement were systematically clarified. Finally, the effects of semi-solid forming parameters, such as the forming temperature, forming ratio and strain rate, on the morphology of the microstructure and the flow stress were also investigated.     

微合金化灰铸铁气焊丝焊接接头组织与性能

以弱碳化焰熔化微合金化灰铸铁焊丝,并充填灰铸铁棒材U型坡口,通过金相观察接头微观组织,发现铸铁同质焊缝微观组织对微合金化元素含量十分敏感,微合金化处理能够实现焊缝金属与基体金属的高强度冶金结合,微合金元素促进焊缝石墨化,并有效避免白口组织及焊接裂纹形成.焊接接头抗拉强度高于基体且硬度接近基体金属,机械加工性能良好.微合金化气焊丝成分可调,可满足各种牌号灰铸铁件的气焊需要.     

A comparative study of viscous polymer processed ceramics based on aqueous and non-aqueous binder systems

Lead zirconate titanate (PZT) is an important piezoelectric material which has wide range of applications as sensors, actuators and transducers. Various forms are required for different devices applications. In this work, extrusion and press forming of PZT ceramic rods and thick films produced via a viscous polymer processing (VPP) route have been investigated. The relationships between the rheology, microstructure and formability of both an aqueous and a non-aqueous polymer binder system have been compared. The non-aqueous PVB system exhibits substantially higher bulk yield stress during plug die flow and higher biaxial extensional stress during squeeze film flow compared to the aqueous PVA system. Discussion of the results is based on differences in the adsorption of the polymer onto the PZT particles and the migration behaviour of the polymer/solvent phase in the two systems.     

硬线钢盘条拉拔断裂分析及工艺改进

针对硬线钢盘条拉拔断裂问题,分别对拉拔性能较差批次的盘条和在拉拔过程中断裂的产品取样,采用光学金相显微镜、拉伸试验机、扫描电镜和能谱仪对其表面质量、化学成分、力学性能、夹杂物、显微组织和中心偏析等分析。结果表明：盘条拉拔断裂的主要原因是盘条中存在中心孔洞及中心碳偏析,其次是在断口存在的Al2O3夹杂物和大颗粒球状夹杂物,在拉拔过程中形成微裂纹并逐步扩展导致断裂。通过确保精炼钢包底吹效果,控制中包过热度及温度波动分别在20～35 ℃和±5 ℃,稳定连铸拉速和波动分别在2 m/min和±0.2 m/min后,铸坯内部缺陷明显减轻,盘条拉拔断裂现象减少。     

光学浮区定向生长Ti-43Al-3Si合金

采用光学浮区定向凝固炉,对Ti-43Al-3Si合金进行引晶定向生长研究.从直径70 mm铸棒中切取直径9 mm多晶棒为籽晶,在5 mm/h的速度下引晶生长出了微观片层平行于生长方向的定向合金.采用OM对获得试样的组织进行观察,结果表明,在开始凝固的L+α+β三相共存区中,多晶棒有效引晶并控制了心部α相,并在曲面生长条件下逐渐发展成为占据主导地位的组织结构.对实验中多晶籽晶的选取、三相共存及曲面生长原理进行了深入讨论.     

Integrated Extrusion-Shear Forming Process of the Solid-State Recycled AZ80 Magnesium Alloy via Hot Press Sintering

The consolidation recycled AZ80 billets were successfully fabricated through the cold press and hot press sintering of the AZ80 metal chips.The consolidation recycled billets sintered at 350℃present the comparable compressive properties and inferior tensile properties compared with the initial cast billets.The defects in the consolidation recycled billet were inclined to propagate along the bond interface between the metal chips during tension,which resulted in the inferior tensile properties of the recycled billets.The recycled billets were then subjected to the integrated extrusion-shear(ES) process.The homogeneous finer dynamic recrystallization grains with an average grain size of 6 μm can be obtained in the shear deformation zone and extrusion sizing zone through integrated ES process at 300℃with an extrusion velocity of 0.6 mm/s.The recycled billets after integrated ES forming process present rival tensile properties compared with the initial cast billets after integrated ES forming with the same extrusion parameters,which can be ascribed to that the integrated ES forming can nearly eliminate the defects through the severe compressive and shear strain.The solid-state recycling process through hot press sintering and subsequent integrated ES process can fabricate the consolidation recycled AZ80 rod,which demonstrates the comparable tensile properties with the cast-extrusion rod.     

电磁复合场协同激光熔覆制备TiBw/Ti网状结构复合涂层

目的利用电磁复合场(EMCF)辅助激光熔覆制备TiB_w/Ti网状结构复合涂层,探索电磁场对涂层组织结构的影响。方法以TiB_2∶Ti=1∶1(摩尔比)的混合粉末为熔覆材料,TC4作为基板材料,通过外加电磁复合场进行激光熔覆试验。通过扫描电子显微镜(SEM)观察洛伦兹力方向对熔覆层组织结构的影响,利用X射线衍射仪(XRD)和维氏显微硬度计分析施加电磁复合场前后熔覆层的相组成和硬度分布。结果未施加电磁复合场的熔覆层组织主要为细针状、粗棒状和颗粒状组织。而施加电磁复合场后,熔覆层出现了网状结构,而且方向向下的洛伦兹力可使涂层内部形成空间间距更大的网状结构。此外,单独施加稳态磁场后,熔覆层只出现细针状和粗棒状组织。电磁复合场施加前后熔覆层硬度与基体相比,均有很大的提高。但未施加电磁复合场的熔覆层硬度变化幅度较大;施加电磁复合场后,随着距熔覆层表面距离的增加,硬度的变化幅度比较平缓。结论在洛伦兹力作用下,可得到TiB_w/Ti网状结构的复合涂层,电磁复合场使TiB_w/Ti网状结构强化相均匀分布,同时提高涂层的显微硬度。     

Enhancing the Mechanical Properties and Formability of Low Carbon Steel with Dual-Phase Microstructures

In the present study, a special heat treatment cycle (step quenching) was used to produce a dual-phase (DP) microstructure in low carbon steel. By producing this DP microstructure, the mechanical properties of the investigated steel such as yield stress, tensile strength, and Vickers hardness were increased 14, 55, and 38%, respectively. In order to investigate the effect of heat treatment on formability of the steel, Nakazima forming test was applied and subsequently finite element base modeling was used to predict the outcome on forming limit diagrams. The results show that the DP microstructure also has a positive effect on formability. The results of finite element simulations are in a good agreement with those obtained by the experimental test.     

速度等高线法优化喷射成形棒坯的形状控制参数

提出并建立了喷射成形棒坯的沉积速度等高线模型,利用计算机数值模拟技术计算了喷射成形空间质量流率分布,找到了沉积器的最佳位置zm与最佳回缩速度v的关系,分析了不同空间位置对沉积坯端面的影响.采用二维坐标跟踪计算了沉积坯的形貌,计算的结果与实际喷射成形铝硅合金棒坯进行了比较,实验结果与预测得到了较好的吻合.     

Fracture toughness and microstructural characterization of polycrystalline rolled tungsten

Various fracture tests have been performed to determine the fracture toughness of sintered and rolled tungsten rods. The polycrystalline rods experienced a degree of deformation of about 65% after sintering and exhibited a pronounced fiber texture. Specimens with three different kinds of crack orientation were extracted and tested in the temperature range between − 150 °C and 950 C. The results confirm the strong influence of the anisotropic microstructure on the fracture behavior and on the brittle-to-ductile transition. To gain insight into the failure mechanisms, a close analysis of the microstructure was done by scanning electron microscopy and electron backscatter diffraction. Furthermore, in situ experiments were conducted at elevated temperatures in the transition regime to study crack initiation and fracture. Auger spectroscopy showed segregations of phosphorus and fluorine at intergranular fracture surfaces.     

Effects of dynamic recrystallization in extruded and compressed AZ31 magnesium alloy

Commercial AZ31 billets were extruded to round rods at three extrusion velocities of 0.8~m/min, 1.4 m/min and 2.2 m/min, at 643 K, 673 K and 703 K, respectively. The microstructure and texture evolution at different conditions were investigated by optical microscopy (OM) and electron backscattered diffraction (EBSD) techniques. The average grain size is reduced significantly after the hot extrusion, and the microstructure is obviously inhomogeneous due to dynamic recrystallization, which is confirmed by uni-axial compression experiments at elevated temperatures with different strain rates. The uni-axial compression leads to a fibre texture, and {1120}<0110> texture is the major texture in extruded rods due to non-basal slip. As the extrusion temperature is elevated, the main texture becomes weak and other texture components appear.