Interface reaction in aluminium matrix composite at laser welding

Interface reaction of SiC w/6061Al aluminium matrix composite subjected to laser welding was studied. It is pointed out that the main reason for bad weldability of the material is concerned with the interface reaction during the welding. Effects of welding parameters on interface reaction were also investigated. The results show that the interface bonding state can be improved by laser beam, and the main welding parameter affecting the strength of weld is laser output power. The smaller the output power, the lower the extent of interface reaction and the better the mechanical properties.

Study on behavior of reinforcement in molten pool for submicron composite Al_2O_3p/6061 Al during laser welding

The behavior of the reinforcement of submicron composite Al_ 2 O_ 3 p/6061Al in molten pool during laser welding was studied. It was indicated that because there were the remarkable differences in thermal physical properties between matrix and reinforcement particulate, the reinforced particulate was pushed forward during molten pool solidification by the liquid-solid interface in matrix and the reinforced particulate segregated in the weld. It resulted in noticeable degradation in properties of the welded joint. The technology methods to improve the behavior of reinforcement were also investigated. It was pointed out that the laser pulse frequency is the main welding parameter affecting the distributive state of reinforcement, and the theory basis was established for welding the material by laser beam.

A review of tool wear prediction during friction stir welding of aluminium matrix composite

Friction stir welding is the preferred joining method for aluminium matrix composites. It is a solid-state process which prevents the formation of the intermetallic precipitates responsible for degradation of mechanical properties in fusion welds of these composites. The major concern in friction stir welding is the wear of the welding tool pin. The wear is due to the prolonged contact between the tool and the harder reinforcements in the composite materials. This paper provides an overview of the effects of different parameters of friction stir welding on the tool wear. It was found that the total amount of material removed from the tool is in directproportion to the rotational speed of the tool and the length of the weld but inversely proportional to the transverse rate. The result seven demonstrate that the tool geometry also has significant influence on the wear resistance of the tool. The tool even converts itself into a self-optimized shape to minimize its wear.

Study on Diffusion Welding Parameters of Particle reinforced Aluminium Matrix Composite Al_2O_(3p) /6061Al

Effects of diffusion welding process parameters on strength of welded joint based on particle reinforced aluminium matrix composite Al 2O 3p /6061Al have been studied through comparing with aluminium matrix alloy. The mechanism for loss of joint strength has been analyzed. It should be pointed out that key processing parameters affecting the strength of joint was welding temperature. The high quality joint can be successfully obtained with appropriate diffusion welding parameters.

PULSED Nd-YAG LASER WELDING OF AN AI-SiC_p METAL MATRIX COMPOSITE

A study is presented of the laser welding behaviour of an SiC particulate re-inforced Al-alloy comPOsite using a pulsed Nd-YAG laser. The influences of laser weldingparameters of laser intensity, pulse duration and the beamjs focus position on the depth ofweld penetration as well as the size of weld bead width were investigated. A typical mi-crostructure of a weld section reveals that the three distinct zones are present. Cracks andporosity were fOund to be two major defects in laser welded metal matrix composites(MMC). These investigations have led to an optimum welding condition proposed forlaser welding of SiC partiulate reinforced aluminium alloy comPosites with minimum de-fects.

Effects of reinforcement on wear resistance of aluminum matrix composites

The effect of reinforcement on the wear mechanism of metal matrix composites （MMCs） was investigated by considering different parameters, such as sliding distance （6 km）, pressure （0.14-1.1 MPa） and sliding speed （230-1480 r/min）. The wear mechanisms of an MMC and the corresponding matrix material under similar experimental conditions were compared on a pin-on-disc wear machine. The pins were made of 6061 aluminum matrix alloy and 6061 aluminum matrix composite reinforced with 10% Al2O3 （volume fraciton） particles （6-18μm）. The disc was made of steel. The major findings are as follows： the MMC shows much higher wear resistance than the corresponding matrix material; unlike that of matrix material, the wear of MMC is very much linear and possible to predict easily; the wear mechanism is similar for both materials other than the three-body abrasion in the case of MMC; the reinforced particles resist the abrasion and restrict the deformation of MMCs which causes high resistance to wear. These results reveal the roles of the reinforcement particles on the wear resistance of MMCs and provide a useful guide for a better control of their wear.

Diffusion bonding mechanism and microstructure ofwelded joint of aluminium matrix composite Al_2O_(3p),/6061

Relationships between microstructures of welded joint and welding parameters or weld strength of aluminium matrix composite Al2O3p/6061 subjected to diffusion welding were studied. The results are as follows: key factor affecting strength of welded joint is oxide in the weld zone. The existence of oxide in the welded joint not only hinders the diffusion of the matrix atoms, but also destroys the good interface between the matrix and the reinforced phase. The oxides turn into fine particles from film with increasing welding temperature, and the destroying effect on welded joint decreases, which increases the strength of the welded joint. On the basis of this, the diffusion welding of aluminium matrix composite Al2O3p/6061 was successfully realized.

Pulse-Impact on Microstructure of Liquid-Phase-Pulse-Impact Diffusion Welded Joints of Particle Reinforcement Aluminum Matrix Composites at Various Temperatures

Investigation was to study the influence of pulse-impact on microstructure of Liquid-Phase-Pulse-Impact Diffusion Welding (LPPIDW) welded joints of aluminum matrix composite SiCp/A356, SiCp/6061Al, Al2O3p/6061Al. Results showed that under the effect of pulse-impact: 1) the interface state between reinforcement particle (SiC, Al2O3) and matrix was prominently;2) the initial pernicious contact-state of reinforcement particles was changed from reinforcement (SiC, Al2O3)/reinforcement (SiC, Al2O3) to reinforcement (SiC, Al2O3)/matrix/ reinforcement (SiC, Al2O3);3) the density of dislocation in the matrix neighboring to and away from the interface in the matrix was higher than its parent composite;and 4) the intensively mutual entwisting of dislocation was occurred. Studies illustrated that: 1) deformation was mainly occurred in the matrix grain;and 2) under the effect of pulse-impact, the matrices around reinforcement (SiC, Al2O3) particles engendered intensive aberration offered a high density nucleus area for matrix crystal, which was in favor of forming nano-grains and improved the properties of the successfully welded composite joints.

STUDY ON DIFFUSION WELDING OF ALUMINIUN MATRIX COMPOSITE

Effects of diffusion welding parameters on strength of welded joint based on particle reinforced alumini- um matrix composite Al2O3p/6061Al were studied by comparing with aluminium matrix alloy,Mecha- nism for the loss of joint strength was analyzed.It was pointed out that the key processing parameters affecting the strength of joint was the welding temperature.The high quality joint can be successfully obtained with appropriate diffusion welding parameters.

THE INTERFACIAL BEHAVIORS OF ALUMINUM MATRIX COMPOSITE IN DIFFERENT WELDING METHODS

Non-interlayer liquid phase diffusion welding (China Patent) and laser welding methods for aluminum matrix composite are mainly described in this paper. In the non-interlayer liquid phase diffusion welding, the key processing parameters affecting the strength of joint is welding temperature. When temperature rises beyond solidus temperature, the bonded line vanishes. The strength of joint reaches the maximum and becomes constant when welding temperature is close to liquid phase temperature. Oxide film in the interface is no longer detected by SEM in the welded joint. With this kind of technique, particle reinforced aluminum matrix composite Al2 O3p/6061Al is welded successfully, and the joint strength is about 80% of the strength of composite (as-casted). In the laser welding, results indicate that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement is restrained intensively at certain laser power and pulsed laser beam. The laser pulse frequency directly affects the reinforcement segregation and the reinforcement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. The maximum strength of the weld can reach 70% of the strength of the parent.

Microstructure and Strength of Laser Welds of Sub-micron Particulate-reinforced Aluminum Matrix Composite Al_2O_(3p)/6061Al

The microstructure of laser welds of sub-micron particulate-reinforced aluminum matrix composite Al_2O_(3p)/6061Al and the weldability of the material were studied. Experimental results indicated that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement was re- strained intenslvely at elevated temperature and pulsed laser beam. The main factor affecting the weldability of the com- posite was the reinforcement segregation in the weld resulting from the push of the liquid/solid interface during the soli- dification of the molten pool. The laser pulse frequency directly affected the reinforcement segregation and the reinfor- cement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. On the basis of this, a satisfactory welded joint of sub-micron paniculate-reinforced aluminum matrix com- posite Al_2O_(3p)/6061Al was obtained by using appopriate welding parameters.

Effect of pulse parameters on microstructure of joint in laser beam welding for SiC_p/6063 composite

The restraint effects of pulse frequency and pulse duty cycle on the precipitates of harmful needle like Al 4C 3 phase were studied in CO 2 impulsed laser welding through the experiment on the SiC p/6063 composite, and the microstructures of the weld under the different process parameters (pulse time from 1 ms to 20 ms,duty cycle from 50% to 91%) were analyzed. In order to compare, CO 2 continuous laser was conducted under the same efficiency. The results demonstrate that the proper laser pulse frequency and duty cycle can restrain the formation of Al 4C 3 effectively. However, the burning loss of SiC is more serious and the fluidity of molten pool is less in continuous laser welding than in impulsed laser welding.

Mechanical Properties of Laser Welded Joints of High Volume Fraction SiCp/Al Aluminum Matrix Composite

High volume fraction SiCp/Al aluminum matrix composite possesses a variety of outstanding properties,such as high thermal conductivity and low coefficient of thermal expansion.It is widely applied in many fields,especially in automotive and aerospace.An orthogonal experiment is conducted to study the effects of relevant parameters on the mechanical properties by CO2 laser.Then the micro-hardness in different regions is measured.The effects of such parameters as laser power,middle layer thickness and welding speed on the tensile strength of the welded joints are discussed.The experimental results indicate that the maximum of the tensile strength of the welded joints is attained at the laser power of 1 200 W,the welding speed of 1.5 m/min and the middle layer thickness of 0.3 mm.In addition,the mechanism of the improvement of micro-hardness on the weld bead is also analyzed.ing technology, surface tribology, wetting behavior and friction reduction.

Cavitation-erosion mechanism of laser cladded SiC particle reinforced metal matrix composite

With 2 kW continuous wave Nd-YAG laser, SiC ceramic powder was laser-cladded on the AA6061 aluminium alloy surface. Within the range of process parameters investigated, the parameters were optimized to produce the SiC_p reinforced metal matrix composites(MMC) modified layer on AA6061 alloy surface. After being treated, the modified layer is crack-free, porosity-free, and has good metallurgical bond with the substrate. The microstructure and chemical composition of the modified layer were analyzed by such detection devices as scanning electronic microscope(SEM-EDX) and X-ray diffractometer(XRD). The performance of electrochemical corrosion and cavitation erosion and their mechanism were estimated by the microhardness tester, potentiostat and (ultrasonic-)(induced) cavitation device.

Effect of tool rotational speed on the particle distribution in friction stir welding of AA6092/17.5 SiCp-T6 composite plates and its consequences on the mechanical property of the joint

This study investigates the effect of tool rotational speed(TRS)on particle distribution in nugget zone(NZ)through quantitative approach and its consequences on the mechanical property of friction stir welded joints of AA6092/17.5 SiCp-T6 composite.6 mm thick plates are welded at a constant tool tilt angle of 2°and tool traverse speed of 1 mm/s by varying the TRS at 1000 rpm,1500 rpm and 2000 rpm with a taper pin profiled tool.Microstructure analysis shows large quantity of uniformly shaped smaller size SiC particle with lower average particle area which are homogeneously distributed in the NZ.The fragmentation of bigger size particles has been observed because of abrading action of the hard tool and resulting shearing effect and severe stress generation due to the rotation of tool.The particles occupy maximum area in the matrix compared to that of the base material(BM)due to the redistribution of broken particles as an effect of TRS.The migration of particles towards the TMAZ-NZ transition zone has been also encountered at higher TRS(2000 rpm).The microhardness analysis depicts variation in average hardness from top to bottom of the NZ,minimum for 1500 rpm and maximum for 2000 rpm.The impact strength at 1000 rpm and 1500 rpm remains close to that of BM(21.6 J)while 2000 rpm shows the accountable reduction.The maximum joint efficiency has been achieved at 1500 rpm(84%)and minimum at 1000 rpm(68%)under tensile loading.Fractographic analysis shows mixed mode of failure for BM,1000 rpm and 1500 rpm,whereas 2000 rpm shows the brittle mode of failure.

Effect of Ti-Si-Mg-Al wire on microstructure and mechanical properties of plasma arc in-situ welded joint of SiC_p/Al composites

The influence of Ti-Si-Mg-AI wire on microstructure and mechanical properties of SiCp/A1 metal matrix composite joints produced by plasma arc in-situ weld-alloying was investigated. Argon-nitrogen mixture was used as plasma gas and Ti-Si-Mg-A1 flux-cored wires as filled composites. Weldments were submitted to tensile test. Meanwhile, the macro morphology and microstructure of the joints were examined. The result shows that the formation ofneedie-like harmful phase A14C3 is effectively inhibited and the wettability of molten pool is improved by adding Ti-Si-Mg-A1 flux-cored wires. With 15Ti-5Si-5Mg-A1 flux-cored wire as filled composite, the maximum tensile strength of the welded joint is 267 MPa, which is up to 83% that of the matrix composites under annealed condition.

激光熔覆WC/316L复合涂层结构及磨损性能

为改善激光熔覆过程中WC增强金属基复合涂层分解与分布不均匀的问题,采用激光熔覆技术制备了50%WC含量的WC/316L复合涂层,分别采用扫描电子显微镜(SEM)、显微维氏硬度计、摩擦磨损试验机表征了熔敷层的组织形貌、硬度与摩擦磨损性能。结果显示,低热输入量可以防止WC颗粒下沉,提升熔覆层厚度方向上的WC颗粒分布均匀性;但WC的平面分布均匀性较差,同时低热输入导致WC颗粒结合较弱,易发生脱落;熔覆过程中,粉末中15%的WC发生分解。研究表明,通过降低激光热输入量,可以制备WC厚度方向较为均匀的复合涂层,提升熔覆层耐磨性,但是需要优化WC平面分布均匀性与WC颗粒结合性能。

SiC_(p)/2024Al复合材料热挤压对激光焊接接头组织性能的影响

采用SiC颗粒增强铝基复合材料替代铝合金制造舰船船体或装甲车体,是解决当前舰船、装甲机动性和防护性二元矛盾的潜在途径。在实际应用过程中因为供货渠道不同,此材料存在不同的状态,这对材料焊接会产生较大的影响。对不同供货状态的SiC_(p)/2024Al复合材料进行激光焊接,对比热挤压前后材料的焊缝成形情况,分析热挤压工艺对焊缝成形以及焊缝接头的物相和显微组织的影响;通过显微硬度,拉伸等力学性能测试,分析复合材料的断裂行为并确定其断裂机理。试验结果表明:热压烧结的SiC_(p)/2024Al复合材料激光焊缝中存在大量的气孔缺陷,接头的最高抗拉强度为76 MPa,仅达到母材强度的28%,焊接后材料强度下降严重;采用热挤压后的复合材料进行激光焊接,焊缝完整,无气孔缺陷,接头没有出现明显的低硬度区域,接头的抗拉强度达到124 MPa,相比于热挤压前的材料焊接接头抗拉强度上升60%;相较于热压烧结的材料,热挤压后的材料焊接性明显增强,接头力学性能有明显的提升。

Laser welding process and strength enhancement of carbon fiber reinforced thermoplastic composites and metals dissimilar joint:A review

Carbon fiber reinforced thermoplastic composites(CFRTP)and metals hybrid structures have been widely used in aircraft lightweight manufacturing.However,due to the significant difference in physical and chemical properties between CFRTP and metals,there are lots of challenges to connect them with high quality.Laser welding has a good application prospect in CFRTP and metals connection,and a significant research progress has been made in the exploration of CFRTP-metal laser joining mechanism,joining process optimization,joining strength improvement and joining defects controlling.However,there are still some problems need to be solved for this technology application.In this paper,the research progress of CFRTP-metal laser joining was summarized in three major aspects:theoretical modeling and simulation analysis,process exploration and parameter optimization,joint performance improvement and process innovation.And,problems and challenges of this technology were discussed,and the outlook of this research was provided.

铝基复合材料搅拌摩擦加工制备工艺及其耐磨性能研究进展

铝基复合材料具有密度低、加工性能良好、耐腐蚀等特点,在高性能制造方面拥有举足轻重的地位,被广泛应用于航空航天、船舶机械等领域。然而,在往复运动的工况条件下,工件之间的磨损对材料的性能影响最为显著,从而降低工件的服役寿命。因此,提高工件耐磨性能和延长服役寿命,对于扩展铝合金的使用范围具有非常重要的意义。在制备铝基复合材料的工艺中,搅拌摩擦加工(Friction stir processing,FSP)技术是制备复合材料的新兴方式之一,所制备的复合材料具有优异的微观组织、不易产生界面反应等特点。所以,搅拌摩擦加工技术在铝基复合材料的生产中有巨大的应用潜力。针对搅拌摩擦加工制备铝基复合材料进行了综述,重点介绍了增强相的种类和含量,以及搅拌摩擦加工中的搅拌道次和焊接等参数,并且讨论了上述因素对铝基复合材料耐磨性能的影响。结果表明:随着增强相含量的增多,铝基复合材料的耐磨性能增强,但过多的含量反而会导致耐磨性能降低;随着搅拌道次的增加,有利于晶粒的细化,但是晶粒的细化程度过高,反而降低了铝基复合材料的耐磨性能。在此基础上,还研究了提高耐磨性能的机理。结果表明,在往复磨损过程中,材料的亚表层易形成动态再结晶,而动态再结晶尺寸对复合材料的耐磨性能有影响,过小的结晶尺寸会使耐磨性能下降。此外,还指出了搅拌摩擦加工制备铝基复合材料过程中存在的问题,如纳米增强相的团聚现象,以及选取适合FSP的工艺窗口等。最后,对FSP未来的研究趋势进行了展望。