LF21超声搅拌摩擦焊接头组织及性能分析

利用超声波对金属塑性成形作用对LF21铝合金进行了超声搅拌摩擦焊接试验,并对常规搅拌摩擦焊与超声搅拌摩擦焊接头的微观组织、断口形貌进行了对比分析.结果表明,超声能量通过搅拌头有效地导入焊缝底部,在增加焊缝底部搅拌强度的同时,提高了搅拌针周围金属原子的运动和扩散能力,焊核区的金属组织有明显的晶粒细化和组织均匀化.超声搅拌摩擦焊断口韧窝数量与深度均不及常规搅拌摩擦焊,撕裂棱不明显;超声搅拌摩擦焊可以提高接头力学性能,但平均断后伸长率相比常规搅拌摩擦焊有所下降.     

2014铝合金搅拌摩擦焊接过程塑性金属流变可视化

采用“标记嵌入技术”对2014铝合金搅拌摩擦焊缝金属塑性流变进行了研究。试验分析结果表明,在搅拌摩擦焊接过程中,焊缝金属材料流动关于焊缝中心线是非对称的,在前进边一侧,既有材料向前流动也有材料向后流动,而在回撤边一侧,材料只发生向后运动;在焊缝上部表面附近,由于搅拌头轴肩的影响,材料向前转移非常明显。建立了二维焊缝金属塑性流变模型,模型能很好地解释焊缝金属流变过程。     

纯铝1060搅拌摩擦微连接焊接力及温度研究

搅拌摩擦焊过程中各物理量的采集分析为理解接头形成过程及质量影响因素提供重要的数据支持.为研究搅拌摩擦微连接过程中焊接力及温度的变化情况,利用自制的监测系统对0.8 mm厚1060-H24超薄铝板搅拌摩擦微连接过程中的焊接力及不同搅拌头转速下的焊缝温度进行了实时测量采集.研究结果表明:搅拌头转速为11000 r/min时焊缝温度最高,达到约350℃,因焊接过程中的搅拌摩擦作用,焊缝金属受热充足流动性好,易形成表面形貌美观且性能优良的搅拌摩擦微连接接头;搅拌头下压驻留后,在初始焊接阶段,焊接轴向力保持在约50 N,持续2 s后因母材受热严重软化导致轴向力开始迅速下降,降至约30 N后稳定焊接.在焊接阶段中焊接横向力始终保持在20～40 N范围内小幅度波动.     

2024-T4铝合金超声辅助搅拌摩擦焊接头组织与性能研究

沿搅拌头方向将超声能量引入对接焊焊缝,利用超声波的振动作用,促进搅拌针周围金属原子的运动和扩散能力,能有效地细化和均匀化焊核区的金属组织,改善焊缝材料的塑性流变行为,增强焊缝底部的搅拌强度,提高搅拌摩擦焊焊接质量和焊接效率。通过对1.8 mm厚2024-T4铝合金进行平板对接焊试验,对比研究了搅拌摩擦焊焊接接头组织与性能。结果表明,超声辅助搅拌摩擦焊能有效减少焊接缺陷,并且接头强度提高了10%,超声辅助搅拌摩擦焊优越性效果明显。     

焊缝金属厚度方向的流动与洋葱瓣花纹的形成

研究了在铝合金薄板与铜箔交替叠加的多层板搅拌摩擦焊过程中焊缝金属的塑性流动行为.结果表明,用带螺纹的搅拌针焊接时,搅拌针周围金属沿螺纹在焊缝厚度方向产生剧烈的流动,在螺纹端部脱离搅拌针并向周围挤压母材,形成实心环形挤压区,与周围母材有明显的界面.洋葱瓣花纹是实心环形挤压区在焊缝横截面上的表现形式.搅拌针表面的螺纹提供金属在焊缝厚度方向流动的驱动力.搅拌头顺时针旋转时,用左螺纹搅拌针焊接的焊缝横截面上,洋葱瓣花纹的中心偏向焊缝底部;用右螺纹搅拌针焊接的横截面上,花纹的中心偏向焊缝表面.     

三维搅拌摩擦焊接过程数值模拟

将搅拌摩擦焊接过程中材料的流动看作是层流、粘性、非牛顿流体绕过旋转的圆柱体,并基于流体力学理论,建立了三维搅拌摩擦焊缝金属塑性流动的数值分析模型.计算结果表明,在焊缝上部表面附近,由于搅拌头轴肩的影响,材料流动比较混乱,发生多次绕流现象;焊缝下部材料流动规律性较明显:只有很少一部分靠近搅拌头探针的材料在焊接过程中受到探针的作用而发生变形和流动,在大多数的模拟条件下,探针直径范围内的材料仅仅在回撤边一侧沿旋转方向绕过探针.焊缝中部具有底部和上部材料的流动特点,是探针和轴肩共同影响的结果.采用"标记嵌入技术"对焊缝金属流动进行可视化研究,试验结果与模拟结果进行了验证,模拟结果能很好地预测塑性金属流动趋势.     

616装甲钢复合热源搅拌摩擦焊工艺

采用氮化硅陶瓷搅拌头外加TIG电弧和背部加热垫板复合的方式对2 mm厚616装甲钢进行焊接试验. 分析了搅拌头转速、焊接速度、TIG电弧的预热电流、背部加热垫板的预热温度等在内的各项焊接参数对焊缝成形的影响,对比了不同参数下焊缝的成形状况,得到了预热参数与搅拌摩擦焊接工艺参数的匹配关系. 结果表明,与传统的搅拌摩擦焊焊缝相比,复合热源焊接的焊缝成形质量得到明显的提高. 在搅拌头转速为1 000～1 200 r/min,焊接速度为35～40 mm/min,预热电流为30～40 A,背部垫板预热温度200 ℃的焊接工艺参数下,能得到成形良好的焊接接头.     

1060铝合金搅拌摩擦焊焊缝金属流动机理

对1060铝合金进行搅拌摩擦焊,研究搅拌头旋转方向、焊接速度、主轴转速和搅拌针偏移方向等不同因素对金属流动的影响。结果表明,5 mm厚1060铝合金在主轴转速1 000~1 100 r/min、焊接速度200~300 mm/min时,可获得无缺陷焊缝。在焊缝上部区域,轴肩的热力作用大于搅拌针对焊缝金属的作用。搅拌针的旋转方向及螺纹旋向对塑性金属流动具有重要影响。当搅拌头偏移的方向不同时,焊接质量相差较大。     

焊接热输入对铝合金双轴肩搅拌摩擦焊缝形貌与接头性能的影响

系统研究了焊接热输入对双轴肩搅拌摩擦焊接头焊核区轮廓和拉伸性能的影响. 接头宏观组织形貌结果表明,随着焊接热输入因子的逐渐升高,双轴肩搅拌摩擦焊接头焊核区依次展现出“哑铃形”、“焊核变平”、“焊核凸出”轮廓. 焊核凸出是高热输入条件下双轴肩搅拌摩擦焊接头特有的一种物理现象,且往往伴随产生内部孔洞型缺陷. 焊核区轮廓形貌取决于双轴肩搅拌摩擦焊缝厚度中心沿径向向外运动的塑性金属流动场与热力影响区中部的相互作用. 拉伸性能结果表明,随着焊接热输入因子的逐渐升高,双轴肩搅拌摩擦焊接头拉伸性能呈现出逐渐下降的趋势.     

搅拌针锥度和螺纹头数对厚板铝合金FSW焊缝金属迁移的影响

研究了20 mm厚2024-T4铝合金板材在搅拌摩擦焊过程中,搅拌针锥度与搅拌针表面螺纹头数对焊缝塑性金属在搅拌针周围迁移程度的影响.结果表明,随搅拌针螺纹头数增加,搅拌头旋转1圈时搅拌针螺纹所转移的高温金属量增加,焊核中塑性金属在前进边和返回边的轴向上迁移程度增加,宏观表现为焊核高度、宽度和面积增大;搅拌针锥度由25°减少至15°时,焊缝塑化金属量增加,焊核塑性金属在焊缝横截面上横向和轴向的迁移程度都增大,焊核面积增大.采用多头螺纹和较小锥度的搅拌针,可以改善厚板焊接时温度梯度大、焊缝金属流动不充分的问题,保证焊缝冶金质量.     

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.     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

A STUDY OF TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE OF TITANIUM

On the basis of energy and shape method for the determination of the valence bond (VB) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is e_c~(2.9907) · (s_c~(0.4980) d_c~(2.4927)) ef1.0093 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.