SiCp/6061Al复合材料的电子束焊缝组织及性能

利用电子束焊焊接了2mm厚的SiCp/6061Al复合材料.通过OM、TEM、SEM、X射线衍射及MTS-810综合实验系统对焊缝组织和性能进行了分析.结果表明,随着热输入的减小,焊缝中的针状的Al4C3(界面反应产物)数量及尺寸均减小.热输入降低到30J/mm时可避免针状Al4C3的形成,焊缝中SiCp分布比母材更均匀.TEM分析表明,焊缝中所有残留的SiCp之表面附近均有Al4C3形成,而针状Al4C3是由许多晶体学位向不一的单晶Al4C3构成.SEM断口分析表明,随着热输入的增大,焊缝的断裂机制发生明显的变化,焊缝强度及塑性下降.     

6061-T6铝合金激光-MIG复合焊接头的组织与性能

本文利用万能材料试验机、金相显微镜、扫描电镜及显微硬度计等分析6061-T6铝合金激光-MIG复合焊接头的组织与性能。研究结果表明,复合焊接头的抗拉强度为165MPa,是母材强度的57％;焊缝区的显微硬度是母材的65％,存在明显的接头软化现象。焊接气孔、接头软化等缺陷严重影响焊接结构的力学性能;焊缝组织主要是等轴晶和柱状晶;接头拉伸断口上分布着许多尺寸较小、形貌相近的等轴韧窝。     

SiCp/6061 Al复合材料激光焊接焊后热处理

SiCp／6061Al复合材料激光熔化焊焊缝显微组织中脆性相Al4C3使焊缝性能严重下降，试验表明：通过适当的热处理可以使针状脆性相Al4C3发生球化，从而提高其机械性能。     

激光-TIG复合熔注制备WCp／Al复合材料层的微观组织

采用激光-TIG复合熔注工艺,在铝合金表面制备WCp/Al表而复合材料层.通过优化激光功率、TIG电流、扣描速度和送粉率等工艺参数,可以捩得0.5～4.3 mm厚的表面复合材料层.采用XRD、SEM、EDS等手段对表面颗粒强化层的微观组织和成分进行研究.结果表明:熔注层基体的微观组织为过共晶组织;熔注层不同位置的过共晶相具有不同的形貌,熔池上部主要为含有十字花状、鱼骨状、蝶状先共晶相(W1-xAlx)Cy的过共晶组织,而底部的先共晶相呈现块状形态.     

喷射共沉积6061Al/SiCp在不同热处理制度下的阻尼性能

采用喷射共沉积方法制备了 6 0 6 1Al/SiCp 金属基复合材料 (MMC) ,研究了 5种热处理制度对其阻尼性能的影响。结果表明 :不同的热处理状态材料 ,常温下其阻尼基本没有变化 ,高温下阻尼则显著不同 ,在 10 0～ 2 70℃温度范围内 ,阻尼能力的大小顺序为炉冷 >空冷 >- 70℃淬火 >原样 (挤压态 ) >- 195℃淬火 >水淬 ,且超过180℃时 ,所有试样的阻尼能力均可达到 1× 10 -2 以上 ;在本研究的温度和应变振幅测试范围内 ,模量随温度的升高表现为单调下降 ,相同频率下的内耗值不随应变振幅变化。     

轧制及T6处理对SiCp/6061Al复合材料拉伸力学性能的影响

对铸态SiC_p/6061Al复合材料分别实施了热轧及热轧+T6处理两种后处理工艺,采用扫描电镜、X射线衍射仪及拉伸试验设备,研究了热轧及T6处理对复合材料显微组织及抗拉强度的影响。结果表明,热轧可以有效地细化铸态SiC_p/6061Al复合材料内的增强颗粒,并消除材料内部孔洞,从而提高材料的抗拉强度。试样在拉伸外力作用下,在增强颗粒与基材间的界面处首先出现裂纹,裂纹扩展后使试样整体断开,热轧后对试样进行T6处理可以有效地消除轧制引起的增强颗粒与铝基材界面处的残余应力,提高增强颗粒与基材间的浸润性,从而提高材料的抗拉强度。在拉伸外力作用下试样中的增强颗粒首先开裂,裂纹扩展后使试样整体断裂。SiC_p/6061Al复合材料随着轧制压缩率的增大,材料的抗拉强度先增大后减小,轧制压缩率为60%的热轧+T6处理的试样在室温和200℃下的抗拉强度均达到最大,分别为350和290 MPa。     

热压烧结-热挤压复合工艺制备SiCp/6061Al基复合材料

采用热压烧结-热挤压复合工艺制备了SiC体积分数为35%的SiCp/6061Al基复合材料。观察了复合材料的金相组织和断口形貌,检测了复合材料的密度和抗拉强度。分析了热压和热挤压复合工艺对复合材料的影响。结果表明:采用热挤压二次成形后,增强体在基体中的分布均匀化,与挤压方向平行;复合材料的致密度达到98.09%,抗拉强度达到248 MPa;基体组织晶粒细化,并产生大量的位错和亚晶组织;SiCp/6061Al复合材料断裂机理主要由6061Al基体的韧性断裂和增强体SiC颗粒的脆性断裂组成。     

焊丝成分对SiCp/6061Al复合材料MIG焊焊缝组织及性能的影响

采用Al-Mg及Al—Si两种焊丝分别对SiCp／6061Al复合材料进行了MIG焊及脉冲MIG焊，利用光学显微镜、电子显微镜及MTS-810试验机对焊缝的组织及性能进行了分析。结果表明，采用Al—Mg焊丝焊接时，无论是MIG焊还是脉冲MIG焊，熔池中Al-SiC间的界面反应程度均较大，生成了较多的针状Al4C3，且Al4C3的尺寸较大。采用Al-Si焊丝时，MIG焊熔池中的界面反应程度显著降低，仅生成了少量尺寸较小的针状Al4C3；而采用Al—Si焊丝的脉冲MIG焊焊缝中没有发现针状Al4C3。同时，利用Al—Si焊丝可有效地防止焊缝熄弧处的宏观结晶裂纹。力学性能试验表明，采用同样焊丝时，脉冲MIG焊接头的强度及伸长率比MIG焊接头的高，而用Al-Si焊丝焊接的接头强度比用Al—Mg焊丝焊接的接头强度高。     

SiCp/Al复合材料与LD2的摩擦焊研究

采用摩擦焊方法对SiCp／Al复合材料与LD2进行连接。焊后借助于光学显微镜对焊接接头进行了微观组织和显微硬度分析。结果表明，在合适的工艺参数下，SiCp／Al复合材料与LD2的摩擦焊焊缝区结合致密，无气孔、夹杂和裂纹等缺陷，其接头强度略高于LD2与LD2的接头强度，因此采用摩擦焊方法焊接颗粒增强型复合材料是可行的。     

热处理对SiCp/6061Al基复合材料等离子弧焊接头性能的影响

热处理对SiCp/6061Al基复合材料等离子弧原位焊接接头组织与性能的影响较为明显,固溶处理 时效与退火相比,前者对接头的改善作用更佳.经500 ℃固溶处理2 h 12 h时效热处理后,接头组织得到良好的改善,细长的Al3Ti相变为短小棒状,消除了晶间偏析,组织更加均匀;热影响区组织中晶粒均得到比较明显的细化,比较接近母材晶粒的大小,焊接接头强度较未热处理时有了较大提高,达到245 MPa.     

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.     

中间层材料对Ti/Al异种金属搅拌摩擦焊组织性能影响

以3mm厚2A14铝合金和TC4钛合金为试验材料,分别添加0.05mmZn和Ni箔片,研究了不同工艺参数下Zn和Ni对接头微观组织、力学性能的影响。试验结果表明：当添加中间层Zn时,在旋转速度为375r/min、焊接速度为75mm/min时,接头抗拉强度达到最大值237.3MPa,为铝合金母材拉伸强度的56.7%。同样参数下,添加中间层Ni后,能显著减少接头中脆性相TiAl₃,接头抗拉强度最大值提高到285.3MPa,达到铝合金母材抗拉强度的68％,接头断裂方式呈脆性+韧性混合型断裂。     

热处理温度对SiCp/6061铝基复合材料激光熔化焊焊缝显微组织的影响

研究了热处理温度对SiCp/6061铝基复合材料激光熔化焊焊缝显微组织的影响.结果表明,热处理温度为480 ℃和580 ℃时,焊缝中针状脆性相Al4C3的形貌,由细长针状断裂为短棒状,继而发生球化;热处理温度为620 ℃和660 ℃时,由于基体中固溶Si含量大幅度提高,抑制了Al4C3的溶解,使焊缝中脆性相Al4C3的形貌没有变化,仍呈针状.采用合适的温度对SiCp/铝基复合材料进行焊后热处理可以改变焊缝中针状脆性相Al4C3的形貌,从而改善焊缝的力学性能.     

AA6061-T6与AZ31合金异种搅拌摩擦焊接头的微观组织

研究了AA6061-T6和AZ31合金异种搅拌摩擦焊接头的微观组织。在异种搅拌摩擦焊接AA6061-T6与AZ31合金时,采用偏置条件,即将搅拌针插入时偏向AZ31合金,从而得到异种对接接头。通过预备实验来优化搅拌针的前进速度、旋转速度。运用电子背散射衍射技术观察搅拌区的纹理,并得到粒径分布和错位角分布,在搅拌区存在相对精细的晶粒结构。在AA6061-T6搅拌区出现随机或弱面取向,而在AZ31搅拌区出现旋转底面取向。再结晶颗粒的平均尺寸只有2．5～4．5μm。与基础合金相比,在AA6061-T6搅拌区的大角度晶界的分数增大,而在AZ31搅拌区的小角度晶界的分数降低。     

Effect of temperature field on types and distribution of reinforcing phases in "in-situ" weld-alloying/PAW of SiCp/6061 Al

Based on theories of heat transfer, physical metallurgy and hydro-mechanical, in order to analyze the effect of welding parameters on species and distribution of reinforcing phases visually and legibly,finite element software ANSYS was used to simulate transient temperature field for SiCp/Al in " in-situ" weld-alloying/plasma arc welding. The results show that the calculated results approximately agreed with the experimental measured results. So the model is basically correct and credible. Based on the numerical solutions and experimental results, effect of temperature field in different welding process parameters( welding current, welding velocity) on species and distribution of reinforcing phases is analyzed. The results show that adjusting and optimizing temperature field appropriately is an effective method to obtain welded joint with better microstructure and property.     

Microstructure and mechanical properties of Al-6061-T6 alloy welded by a new hybrid FSW/SSW joining process

In this study for the first time, the effects of decrease in heat inflow to the weld metal in friction stir process by utilising semisolid processing and decreasing the pin rotational speed as well as increasing the pin transverse speed were examined. As a result, the characteristic loss of hardness and strength in the weld zone were eliminated. The results showed that by approaching the ultrafine microstructure in the weld zone through the hybrid FSW/SSW process, the hardness and elongation values reached to 90?Hv and 8.88%, respectively. These are only slightly different from those of the base metal of the welded samples. Furthermore, the ultimate tensile strength of the samples welded by the hybrid technique was found to be about 167?MPa that was higher than those of the samples welded by friction stir welding (151?MPa) and semisolid welding (114?MPa) techniques.     

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。     

SiC颗粒增强铝基复合材料氦-氩混合气体TIG焊研究

以氦-氩混合气体为保护气氛,采用填加铝硅焊丝的方法对SiC颗粒增强铝基复合材料进行了TIG焊的研究.获得良好焊逢的最佳工艺参数为:焊接电流60A,氦-氩混合气体流量115 mL/s,焊接速度3.2 mm/s.金相组织观察表明,焊缝区全部由均匀细小的等轴晶组成,热影响区组织较粗大.焊件的抗拉强度为母材的70%左右,断裂发生在热影响区,属于韧-脆混合断裂.     

Microstructural characterization and mechanical properties of aluminum 6061-T6 plates welded with copper insert plate (Al/Cu/Al) using friction stir welding

Friction stir welding was used to join two aluminum 6061-T6 plates with an insert of a pure copper plate (Al/Cu/Al), and then the influence of the copper insert on the joint performance was studied. The dissimilar welding results were also compared with AA 6061 friction stir welds produced without copper insert (Al/Al). Optical and scanning electron microscopes were used for the microstructural observations of the welded samples. X-ray diffraction analysis was used to analyze phase component of the Al/Cu/Al specimen. A defect-free joint was observed for the Al/Cu/Al joint at a rotational speed of 950 r/min and a welding speed of 50 mm/min. Microstructural observation of the weld nugget zone (WNZ) demonstrates the formation of composite-like structure which promotes metallurgical bonding of aluminum and copper. XRD results show the formation of intermetallic compounds (IMCs), such as Al₄Cu₉ and Al₂Cu. Furthermore, it was observed that the hardness of the weld with the Cu insert plate is higher than that of other samples due to more dislocation density and a distinct rise in hardness values was observed due to the presence of IMCs. The ultimate tensile strength of the joint with copper insert plate is higher than that of the other sample due to the strong metallurgical bonding between Al and Cu.     

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.