Joining of SiCp/Al composites by insert powder layers

Mixed Al-Si, Al-Si-SiC and Al-Si-W powders were employed as insert layers to reactive diffusion bond SiCp/6063 MMC. The results show that SiCp/6063 MMC joints bonded by the insert layer of the mixed Al-Si powder have a dense joining layer with a typical hypoeutectic microstructure. Using mixed Al-Si-SiC powder as insert layer, SiCp/6063 MMC can be reactive diffusion bonded by a composite joint. Because of the SiC segregations, however, there are a number of porous zones in the joining layer, which results in the low shear strength of the joints, even lower than that of joints reactive diffusion bonded by the insert layer of mixed Al-Si powder. The W added into the insert layer of Al-Si-W nearly all reacts with Al to form intermetallic WAl12 during bonding. The reaction between the W and Al facilitates to form a dense joint of high quality, and the formed interrnetallic WAl12 has a reinforcing effect on the joints, which lead to the high shear strength of the joints. In general, under the condition of fixed bonding time （temperature）, the shear strengths of the joints increase as the bonding temperature （time） increases, but tend to a maximum at bonding temperature of 600℃ （time 90 min）.     

In-situ weld-alloying plasma arc welding of SiCp/Al MMC

Plasma arc welding was used to join SiCp/ml composite with titanium as alloying filler material. Microstructure of the weld was characterized by an optical microscope. The results show that the harmful needle-like phase Al4C3 is completely eliminated in the weld of SiCp/Al metal matrix composite（MMC） by in-situ weld-alloying/plasma arc welding with titanium as the alloying element. The wetting property between reinforced phase and Al matrix is improved, a stable weld puddle is gotten and a novel composite-material welded joint reinforced by TiN, AlN and TiC is produced. And the tensile-strength and malleability of the welded joints are improved effectively because of the use of titanium.     

等离子弧焊接SiCp/Al基复合材料焊缝“原位”合金化分析

采用等离子弧焊焊接SiCp／Al基复合材料,以Ar＋N2为离子气,并以Ti作为合金化填充材料,研究了焊缝“原位”合金化元素Ti对焊缝显微组织的影响。结果表明,采用焊缝原位合金化方法焊接SiC颗粒增强铝基复合材料（sicp／A1MMCs）,可以有效抑制焊缝中针状脆性相Al4C3的形成,并且由于耶的加入,改善了增强相和Al基体之间的润湿性,形成了稳定的熔池,得到以均匀分布的TiN、AlN等为增强相的新型铝基复合材料焊缝,焊接性能得到有效提高。同时还研究了Ti的添加量对焊缝显微组织的影响,结果发现,随着耶含量的增加,焊缝中还生成如Ti5Si3等新的增强相。焊缝“原位”合金化等离子弧焊接是焊接SiCp／Al基复合材料的一种新方法。     

热处理及致密度对高体积分数SiCp/Al复合材料性能的影响

研究了致密度及不同热处理状态对SiCp／A1复合材料的抗弯强度和热膨胀系数的影响。结果表明，致密度对材料的抗弯强度的影响很大，当致密度为94％N98，5％时，强度分别为321及389MPa，相差约70MPa。热处理对复合材料的抗弯强度及热膨胀系数有较大的影响，T6态时的强度达到410MPa，但热膨胀系数减小：而原始态、时效态和退火态的抗弯强度依次降低，热膨胀系数依次升高（在400℃以下）。     

颗粒级配对SiCp／Al复合材料摩擦磨损性能的影响

采用销-盘摩擦磨损试验机,考察了高体积分数SiCp/Al复合材料中颗粒尺寸及颗粒级配等组织因素对材料干摩擦磨损性能的影响.通过磨损表面的SEM形貌分析,研究了复合材料的磨损机理.结果表明,与灰铸铁配副时,材料的摩擦系数与磨损率明显依赖于碳化硅颗粒尺寸,二者均随颗粒尺寸的增大而先降低后增大.采用颗粒级配方法能明显改善复合材料的干摩擦磨损性能.粗细颗粒问的级配具有相互强化的作用,有利于降低摩擦系数和磨损率,并使其趋于稳定.复合材料的磨损以对偶件材料的转移和犁沟为特征.     

Effects of ac arc ultrasonic on plasma arc in situ welding of SiCp/6061Al MMCs

Abstract

The isolation coupling device is designed based on the principle of high pass filter circuit, which can achieve isolation and coupling between ac welding power and ultrasonic frequency excitation source. In addition, ac arc ultrasonic vibration is obtained successfully. The plasma arc in situ welding of SiCp/6061Al was performed using two different processes. The first process is that the plasma gas is argon nitrogen mixture and the filler material is flux cored wire (Al–5Ti–5Si); the other process is that the plasma gas is argon and the filler material is flux cored wire (Al–15Ti–3Si). The two joints are respectively enhanced by nitride and Al₃Ti, which were obtained in these processes. After arc ultrasonic vibrations were imposed on the two welding processes, it was revealed that arc ultrasonic improved the distribution of the new nitride phases and optimised the morphology of Al₃Ti to improve the mechanical properties of joints that reached 246 and 263 MPa. Fracture analysis showed that the improvement of the mechanical properties resulting from Al₃Ti is better than that from nitride under the effect of arc ultrasonic.     

Effect of Ti-Al on microstructures and mechanical properties of plasma arc in-situ welded joint of SiCp/Al MMCs

The effect of Ti-Al on microstructures and mechanical properties of SiCp/Al MMC joints produced by plasma arc in-situ weld-alloying was investigated, in which argon-nitrogen mixture was used as plasma gases and Ti-Al alloy as filling composite. The results show that the formation of needle-like harmful phase Al4C3 is effectively prevented in the weld by in-situ weld-alloying/plasma arc welding with Ti-Al alloy sheet filler whose titanium content is more than 20%. The fluidity of molten pool is improved, and stable molten pool is gained for the addition of the Ti-Al alloy. The mechanical properties of welded joint are effectively enhanced by the compact-grain structure and the new reinforced composites such as Al3Ti, TiN, AlN and TiC welded joint. The test results of mechanical property show that the maximum tensile strength of welded joint gained by adding Ti-60Al alloy is up to 235 MPa. The factors influencing the tensile strength were also investigated.     

Effect of Ti-Al on microstrucmres and mechanical properties of plasma arc in-situ welded joint of SiCp/A1 MMCs

The effect of Ti-Al on microstructures and mechanical properties of SiCp/Al MMC joints produced by plasma arc in-situ weld-alloying was investigated, in which argon-nitrogen mixture was used as plasma gases and Ti-Al alloy as filling composite. The results show that the formation of needle-like harmful phase Al4C3 is effectively prevented in the weld by in-situ weld-alloying/plasma arc welding with Ti-Al alloy sheet filler whose titanium content is more than 20%. The fluidity of molten pool is improved, and stable molten pool is gained for the addition of the Ti-A1 alloy. The mechanical properties of welded joint are effectively enhanced by the compact-grain structure and the new reinforced composites such as Al3Ti, TiN, AlN and TiC welded joint The test results of mechanical property show that the maximum tensile strength of welded joint gained by adding Ti-60Al alloy is up to 235 MPa. The factors influencing the tensile strength were also investigated.     

热处理工艺对A356/SiCp性能及干滑动摩擦磨损特性的影响

研究分析热处理工艺对A356/SICp复合材料的硬度、导电率及微观组织的影响,在此基础上研究复合材料的干滑动摩擦磨损特性.结果表明:固溶和T6热处理可显著提高复合材料的硬度,但降低导电率,而低温退火却比较显著地提高导电率;导电率高的低温退火态磨损特性基本与铸态一致,固溶处理及时效处理虽可有效提高硬度,但不提高耐磨性能,这表明T6热处理是否作为制动盘材料时的最佳热处理工艺,有待进一步研究;复合材料的磨损率随载荷的增加而增加,但低载荷时增加缓慢,高载荷时增加迅速;摩擦因数随着热处理工艺而变化,但对载荷变化不敏感,都在较小的范围内波动,基本是稳定的.     

SiCp/Al基复合材料的混粉电火花加工工艺实验

利用混粉电火花加工方法对SiCp/Al基复合材料进行了工艺实验.着重研究了在SiCp/Al基复合材料加工中不同工艺条件尤其是电参数、铝粉粉末对加工效果的影响规律,积累了一定量的工艺数据,形成了一套完整的工艺方案.     

Study on diffusion welding SiCp/ZL101 with Cu interlayer

Through the vacuum diffusion welding SiCp/ZL101 aluminum with Cu interlayer,the effect of welding parame-ter and the thickness of Cu on the welded joint property was investigated,and the optimal welding parameters were putforward at the same time.The microstructure of joint was analyzed by means of optical-microscope,scanning electron mi-croscope in order to study the relationship between the macro-properties of joint and the microstructure.The results showthat diffusion welding with Cu interlayer could be used for welding aluminum matrix composites SiCp/ZL101 successfully.     

加Ti箔中间层的钼-钼扩散焊接

在1000℃、10 MPa、60 min的工艺条件下,添加5μm的Ti箔作为中间层材料,进行钼-钼基体之间的真空扩散焊接.利用扫描电镜(SEM)观察接头界面形貌,并利用其自带的X射线能谱仪对界面元素扩散情况和中间层区域的元素成分进行测试和分析.结果表明,添加Ti箔作中间层实现钼-钼真空扩散焊接时,Ti原子和Mo原子能够实现良好的扩散,界面区域均为Mo-Ti固溶体,界面焊合率100％.     

SiCP／Al复合材料的显微结构分析

采用粉末冶金＋热挤压工艺制备SiCp/Al复合材料，测定其力学性能。利用X射线衍射分析复合材料物相的组成，用金相显微镜、扫描电镜和透射电镜分析其微观组织结构。结果表明，SiC颗粒在铝基体中分布比较均匀，SiC颗粒与基体结合良好；基体主要是α-Al，强化相β-Mg2Si和弥散相（Fe，Mn，Cu）3Si2Al15（体心立方结构，晶格常数1．28nm）；SiCp／Al界面则为Al和Mg元素扩散到SiC表面的SiO2层形成的20nm-30nm无定形层；复合材料的断裂机制主要是SiC颗粒断裂和SiCp／Al界面塑性撕裂：复合材料在变形过程中，SiC颗粒可阻止裂纹的扩展。     

SiCp/Al基复合材料的高压扭转试验

采用高压扭转（high-pressure torsion,HPT）工艺制备SiCp/Al基复合材料,试验发现随着扭转半径的增加,剪切应变增大,SiC颗粒分布逐渐均匀;升高温度,SiC颗粒分布的均匀性好;随着扭转半径的增加材料的硬度先增加后减小,且材料越致密,SiC含量越多,分布越均匀,材料硬度越高。     

铸造法制备SiCp/Al复合材料的研究现状

本文综述了铸造法(搅拌铸造法、挤压铸造法、离心铸造法)制备SiCp/Al复合材料的研究现状,指出了铸造法中存在的主要问题以及今后的研究方向.     

活化剂对自浸渗法制备SiCp／Al复合材料的影响

研究了以K2TiF6为助渗剂,Mg及La2O3为活化剂,在大气条件下无压力自浸渗制备颗粒增强铝基复合材料的新方法。结果表明,加入活化剂阻止了复合材料中脆性相Al3Ti,Al4C3的产生。此方法对改善自浸渗法制备SiCp/Al复合材料的组织与性能起到关键的作用。     

Al/SiCp复合材料的断裂行为

采用粉末冶金和喷射沉积方法制备了Al及Al／SiCp复合材料，测试了材料的力学性能，利用金相显微镜和扫描电镜观察了材料的断裂行为。结果表明，Al／SiCp复合材料的强度比基体材料的高，但塑性低。粉末冶金方法制备的Al／SiCp复合材料与喷射沉积方法制备的比较，前者组织更致密，强度更高，塑性更好，断裂是SiC颗粒开裂，裂纹的传递主要沿颗粒中形成的裂纹扩展；后者断裂主要表现为SiC颗粒从基体中拔出，裂纹的传递大多是SiC颗粒周围形成的裂纹在基体中扩展。     

搅拌铸造制备SiCp/Al复合材料的研究现状

综述了搅拌铸造制备SiCp／Al复合材料的研究现状,指出了搅拌铸造法存在的问题,对搅拌铸造法在制备SiCp/Al复合材料中的地位和发展前景作了预测。     

SiC_p/Al高速电弧放电加工研究

研究了高速电弧放电加工铝基碳化硅增强复合材料(Si Cp/Al)的性能。通过对体积分数为20%的碳化硅颗粒增强铝基复合材料进行加工实验得出:在峰值电流500 A、脉冲宽度10 ms时,材料去除率超过8200 mm3/min,电极损耗率约为2%。此外,研究了加工极性对工件表面质量的影响,得出电极负极性、大电流可用于大余量材料去除,电极正极性、小电流可用于小余量表面修整的结论。最后,采用高速电弧放电加工实现了碳化硅颗粒增强铝基复合材料的钻孔、铣削和切割等加工工艺。     

SiCp/Al复合材料脉冲激光焊接研究

研究了SiCp/Al复合材料的脉冲激光焊接。重点讨论了激光光强，脉冲作用时间及激光束聚焦位置等参数对焊缝熔深和宽度的影响；讨论了其界面反应对焊接接头力学性能的影响。研究结果表明，SiCp/Al复合材料的激光焊接区存在着3个组织性能明显不同的区域。