反向压铸SiCw/Al复合材料及其均匀性研究

采用反向压铸技术制造SiCw（ψ=18%）/6061Al复合材料。在复合材料不同部位取样，测量SiCw昌须体积分数，借助扫描电镜观察SiCw分布情况，测量SiCw形貌参数。结果表明，反向压铸复合材料具有良好的均匀性。     

SiC晶须对SiCw/6061Al复合材料拉伸和压缩变形行为的影响

通过试验研究了SiCw/6061Al复合材料和6061Al基体的拉伸和压缩变形行为.结果表明,SiCw/6061Al复合材料和6061Al的拉伸变形行为相同,而压缩变形曲线上出现应力峰,这与不同应力状态下SiC晶须的转动有关.拉伸时SiC晶须逐渐转向与外力平行方向使SiCw/6061Al复合材料的应力增大,而压缩时SiC晶须转向与外力垂直方向使其应力减小,而不是由动态再结晶引起.     

SiCw/6061Al复合材料冲击破坏行为

本文用夏比冲击试验(Instrumented Charpy Testing)与SEM断口分析研究了SiCw/6061Al复合材料的冲击破坏行为.与SiCw是混乱分布的铸态SiCw/6061Al复合材料相比,挤压变形后材料的冲击韧性明显提高.热挤压变形改善了材料的性能.研究观察发现了分层开裂的现象.本文详细讨论了SiCw/6061Al复合材料的冲击断裂方式、比较了变形前后冲击破坏方式的差异,并分析了热挤压变形后韧性提高的原因.     

SiCw/Al复合材料的低周疲劳性能

一、前言 SiCw/Al复合材料具有优异的力学性能和物理性能,是一种正在得到实际应用的新型结构材料。疲劳是零构件最常见的失效形式之一。对于SiCw/Al复合材料的高周疲劳性能和疲劳裂纹的萌生与扩展已有较多研究,结果表明,该材料具有比基体Al合金更高的高周疲劳强度和更高的疲劳裂纹扩展门槛值。然而,对SiCw/Al的低周疲劳性能报道得有限。因此,本文研究了挤压铸造法制造的16％Vf-SiCw/Al复合材料在控制总应变条件下的低周疲劳性能,并和6O61Al合金进行了比较。 二、实验过程 所用材料为挤压铸造法制造的SiCw体积分数为16％的SiCw/6061Al复合材料和工业用6061Al合金。SiCw选用日本东海碳素公司生产的β-SiC。 SiCw/6061Al制备后对其进行了热挤压,挤压比为1:22。热处理状态选用自然时效和人工时效。固溶温度为520℃。自然时效为室温时效5O天。人工时效选用两种条件:一为150℃×10h,一为170℃×15h。热处理后,用电火花切割机将SiCw/6061Al及6061Al切割成板状试样。试样工作部分长12mm,截面积为2.5mm×5mm。所有试样的两个表面都进行了仔细的机械抛光,侧面也用     

正挤压对SiCw/6061Al晶须形貌的影响

为了研究正挤压加工对SiCw/6061Al复合材料晶须形貌的影响规律,通过改变挤压温度、挤压比等工艺条件正挤压成形了挤压铸造法制备的15vol.%SiCw/6061Al复合材料,利用SEM技术观察和分析了正挤压加工前后复合材料的微观组织形貌.研究表明:正挤压加工导致SiC晶须沿着复合材料的塑性流动方向呈现出一定程度的定向排列趋势,并伴随有比较明显的折断现象;挤压温度、挤压比等工艺参数都是影响SiC晶须形貌的主要因素.     

合金化填充材料Ni 对SiCP/6061Al 复合材料激光焊接焊缝显微组织的影响

以N i 片作为合金化填充材料对SiC_P/6061A l 金属基复合材料(SiC_P/6061A lMMC) 进行激光焊接, 研究了激光输出功率、焊接速度等焊接工艺参数对焊缝显微组织的影响。结果表明, 采用金属N i 片作为合金化填充材料对SiC_P/6061A lMMC 进行激光焊接, 可以在一定程度上抑制SiC 颗粒的溶解及针状脆性相Al₄C₃ 的形成, 并获得以Al₃Ni 等相为增强相的焊缝显微组织, 但在焊缝心部有粗大的气孔形成。      

SiCw/Al基复合材料的腐蚀机理与防护探讨

本文主要探讨了SiCw/Al基复合材料的腐蚀机理与防护方法。SiC晶须加入到铝基复合材料中,致使SiCw/Al基复合材料的钝化膜不连续,从而造成孔蚀。孔蚀和电偶腐蚀是SiCw/Al基复合材料的主要腐蚀形态。对SiCw/Al基复合材料施加保护层可以大幅度提高其耐腐蚀性能。     

变形温度对SiCW/6061Al复合材料压缩变形期间基体金属流动和晶须重新取向的影响

借助观察和分析变形前后晶须取向和试样形状的变化，研究了晶须呈定向排列的SiCw/6061Al复合材料压缩变形期间金属流动和晶须重新取向的现象。研究结果表明，由于晶须的定向排列，SiCw/6061Al复合材料压缩变形期间基体金属的流动和晶须的重新取向强烈地依赖于变形温度。在较高温度压缩变形时，基体金属可以更均匀地流动，此时晶须是否发生重新取向与变形时环状和柱状试样的应变场有关；在较低温度变形时晶须不发生重新取向。     

含Mg药芯焊丝对SiCp/6061Al等离子弧原位焊接的影响

针对SiCp/6061Al基复合材料焊接接头中增强相颗粒发生偏聚,使接头强度降低的问题,采用不同Mg含量的药芯焊丝(合金元素Al-Ti-Mg)为填加材料,以氩氮混合气为离子气,对SiCp/6061Al基复合材料进行等离子弧原位合金化焊接,研究了该类药芯焊丝对焊接接头组织和性能的影响.研究表明,当焊丝中Mg含量达到15%...     

空心陶瓷/铝基复合材料的阻尼减振性能

采用挤压铸造法制备了70%(体积分数)空心陶瓷/6061Al复合材料,采用弯曲共振法测试了复合材料的阻尼性能.结果表明,空心陶瓷的加入明显提高了6061Al合金的阻尼性能,且尺寸减小会进一步提高空心陶瓷复合材料的阻尼性能.采用弯曲共振法测得的含较小粒径的空心陶瓷/6061Al复合材料的阻尼为基体6061Al阻尼的5.7倍,这表明空心陶瓷/6061Al复合材料阻尼与材料内部所含孔洞有密切的关系.结合组织观察,本文对相关的阻尼机理进行了探讨.     

Study on Laser Welding of Al Composite

The effects of laser welding parameter on strength of welded joints were studied. The mechanism for loss of joint strength was analyzed. It was pointed out that an important factor affecting joint strength is the reaction between matrix and reinforced phase. On the basis of this, the concept of critical St activity a[si]min was proposed. Using appropriate welding parameters and Si activity, high quality laser welded joints in an aluminum matrix composite SiCw/6061Al can be Successfully obtained.     

Research on laser welding of aluminum matrix composite SiCw/6061

Effects of laser welding parameters on strength of welded joint were studied. Mechanism of loss of joint strength was analyzed. It was pointed out that an important factor affecting joint strength is the reaction between matrix and reinforced phase. On the basis of this, the concept of critical Si activity was proposed. In appropriate welding parameters and Si activity, welded joint with high quality for aluminum matrix composite SiCw/6061Al subjected to laser welding could be successfully obtained.     

Investigation on TIG welding of SiCp-reinforced aluminum–matrix composite using mixed shielding gas and Al–Si filler

Using He–Ar mixed gas as shielding gas, the tungsten inert gas (TIG) welding of SiCp/6061 Al composites was investigated without and with Al–Si filler. Welded joint with filler were submitted to tensile tests. The microstructure and fracture morphology of the joint were examined. The results show that adding 50 vol.% helium in shielding gas improves the arc stability, and seams with high-quality appearance are obtained when the Al–Si filler is added. In addition, the interface reaction between SiC and matrix is greatly suppressed when using Al–Si filler. The microstructure of the welded joint displays non-uniformity with many SiC particles distributing in the weld center. The average tensile strength of weld joints with Al–Si filler is 70% above that of the matrix composites under annealed condition.     

Single-sided laser beam welding of a dissimilar AA2024–AA7050 T-joint

In the aircraft industry double-sided laser beam welding of skin–stringer joints is an approved method for producing defect-free welds. But due to limited accessibility – as for the welding of skin–clip joints – the applicability of this method is limited. Therefore single-sided laser beam welding of T-joints becomes necessary. This also implies a reduction of the manufacturing effort. However, the main obstacle for the use of single-sided welding of T-joints is the occurrence of weld defects. An additional complexity represents the combination of dissimilar and hard-to-weld aluminium alloys – like Al–Cu and Al–Zn alloys. These alloys offer a high strength-to-density ratio, but are also associated with distinct weldability problems especially for fusion welding techniques like laser beam welding. The present study demonstrates how to overcome the weldability problems during single-sided laser beam welding of a dissimilar T-joint made of AA2024 and AA7050. For this purpose a high-power fibre laser with a large beam diameter is used. Important welding parameters are identified and adjusted for achieving defect-free welds. The obtained joints are compared to double-sided welded joints made of typical aircraft aluminium alloys. In this regard single-sided welded joints showed the expected differing weld seam appearance, but comparable mechanical properties.     

SiCp/Al复合材料焊接综述

为实现SiCp/Al复合材料的高质量可靠焊接,推广SiCp/Al复合材料在各领域的应用,调研了国内外SiCp/Al复合材料不同焊接方法的研究现状。在熔化焊方面,国内外学者通过调整工艺参数、在焊缝中加入Ti元素发生诱发反应等方法,抑制了焊缝中Al4C3针状脆性相的形成,从而提高了焊接接头的力学性能。在搅拌摩擦焊方面,国内外学者针对不同材料设计了专用的焊接搅拌头,以保证它们具备高耐磨性与足够的冲击韧性,在焊接过程中不出现破损情况;关注了焊接过程中焊接头转速、焊接速度、轴向力与热输入等因素,以获得力学性能优秀、晶粒细小均匀的焊接接头。在扩散焊方面,国内外学者探究了中间夹层对焊缝界面间原子相互扩散的促进作用;采取不同工艺参数,以外加超声或电子束表面加热等方式促进了原子间的相互扩散,以获得力学性能优异的焊接接头,提高焊接效率。在钎焊方面,国内外学者通过探究钎料与SiCp/Al复合材料之间的润湿性来组合钎料与钎剂,通过化学腐蚀处理表面暴露颗粒增强相、在复合材料表面电镀金属等方法来增大钎料与增强相的润湿性、解决钎料铺展受阻的问题,以进一步提高钎焊焊接接头质量。     

Evolution of microstructures and mechanical properties in similar and dissimilar friction stir welding of AA5086 and AA6061

In this work, thermo-mechanical behavior and microstructural evolution in similar and dissimilar friction stir welding of AA6061-T6 and AA5086-O have been investigated. Firstly, the thermo-mechanical behaviors of materials during similar and dissimilar FSW operations have been predicted using three-dimensional finite element software, ABAQUS, then, the mechanical properties and the developed microstructures within the welded samples have been studied with the aid of experimental observations and model predictions. It is found that different strengthening mechanisms in AA5086 and AA6061 result in complex behaviors in hardness of the welded cross section where the hardness variation in similar AA5086-O joints mainly depends on recrystallization and generation of fine grains in weld nugget, however, the hardness variations in the weld zone of AA6061/AA6061 and AA6061/AA5086 joints are affected by subsequent aging phenomenon. Also, both experimental and predicted data illustrate that the peak temperature in FSW of AA6061/AA6061 is the highest compared to the other joints employing the same welding parameters.     

Microstructure characteristics of thick aluminum alloy plate joints welded by fiber laser

It's difficult to weld high strength thick plate since the groove is huge when using traditional arc welding, and the weld tends to be softened and large deformation could occur after multi-layer welding. All of these can affect the industrial application of high strength thick plate wielding. In this case, developing advanced welding technology and welding material is necessary to optimize the microstructure and performance of the welds. Fiber laser has many advantages such as good monochrome and high quality laser beam. In order to decrease the heat damage to the base metal from the welding heat source, low heat input is employed for welding thick plate. Fiber laser is applied in the welding of 20 mm thick Al–Zn–Mg–Cu alloy with super narrow gap filler wire. The microstructure comparison of Al–Mg–Mn alloy and Al–Mg–Mn–Zr–Er alloy welded joints reveals that a huge amount of fine equiaxed grains is formed in the weld zone of Zr and Er micro-alloying Al–Mg–Mn alloy welding wire and a great number of precipitation strengthening phases are precipitated in the weld zone after the heat treatment of welded joints in the entirety.     

Comparative experimental study on the modification of microstructural and mechanical properties of friction stir welded and gas metal arc welded EN AW‐6061 O aluminum alloys by post‐weld heat treatment

In this paper, the effects of post‐weld heat treatment on modification of microstructures and mechanical properties of friction stir welded and gas metal arc welded AA6061‐O plates were compared with each other. Gas metal arc welding and friction stir welding were used as the applicable welding processes for AA6061‐O alloys. The applied post‐weld heat treatment consisted of solution heat treatment, followed by water quenching and finally artificial aging. The samples were classified as post‐weld heat treated and as‐welded joints. The microstructural evolution, tensile properties, hardness features and fracture surfaces of both as‐welded and post‐weld heat treated samples were reported. The results clearly showed that friction stir welding process demonstrated better and more consistent mechanical properties by comparison with the gas metal arc welding process. The weld region of as‐welded samples exhibited a higher hardness value of 80 HV0.1 compared to the base material. In addition, the feasibility of post‐weld heat treatment in order to enhance the mechanical properties and to obtain more homogeneous microstructure of 6061‐O aluminum alloys was evaluated.     

Tensile Fracture Location Characterizations of Friction Stir Welded Joints of Different Aluminum Alloys

The tensile fracture location characterizations of the friction stir welded joints of the AA1050-H24 and AA6061-T6 Al alloys were evaluated in this study. The experimental results show that the fracture locations of the joints are different for the different Al alloys, and they are affected by the FSW parameters. When the joints are free of welding defects, the AA1050-H24 joints are fractured in the HAZ and TMAZ on the AS and the fracture parts undergo a large amount of plastic deformation, while the AA6061-T6 joints are fractured in the HAZ on the RS and the fracture surfaces are inclined a certain degree to the bottom surfaces of the joints. When some welding defects exist in the joints, the AA1050-H24 joints are fractured on the RS or AS, the AA6061-T6 joints are fractured on the RS, and all the fracture locations are near to the weld center. The fracture locations of the joints are dependent on the internal structures of the joints and can be explained by the microhardness profiles and defect morpho     

Interfacial characteristics of electron beam welding joints of SiCp/Al composites

Abstract

The electron beam welding of SiCp/101Al composites has been carried out. The influence of welding parameters on weldability and mechanical properties of the welded joints was discussed. The welding parameters were therefore optimised under the current experimental circumstance. Results show that only weak interfacial reaction between SiC particle and liquid aluminium occurred. Minute quantity brittle Al₄C₃ compounds and single phase Si were generated in the welded joint. The interfacial reaction between SiC particles and Al matrix could be greatly suppressed by adopting appropriate technique measures such as high welding speed and low heat input. The content of Al₄C₃ can be therefore greatly decreased in the welded joint. Moreover, modification welding and electron beam scanning could further improve the appearance of weld, and the welded joint with better quality could be obtained.