Effect of Welding Paramenter on Joint Property of Aluminum Matrix Composite in Liquid-Phase-Impacting Diffusion Welding

In this paper, a new method for welding SiCp/101A was put forward. It is LPI (liquid-phase-impacting) diffusionwelding. Through LPI diffusion welding SiCp/101A aluminum, the effect of welding parameters on the weldedjoint property was investigated, and the optimal welding parameters were brought forward at the same time. Themicrostructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to studythe relationship between the macro-properties of joint and the microstructure. The results show that LPI diffusionwelding could be used for welding aluminum matrix composites SiCp/101A successfully.

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.

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.

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.

Liquid-Phase-Impacting Diffusion Welding Mechanism and Microstructure of Welded Joint of Al Matrix Composite SiCp/101A

The liquid-phase-impacting (LPI) diffusion welding mechanism and microstructure of welded joint of aluminum matrixcomposite SiCp/101A have been studied. It shows that by LPl diffusion welding, the interface state between SiCparticle and matrix is prominent, the harmful microstructure or brittle phase can be restrained from the welded joint.Moreover, the density of dislocation in the matrix near the interface and in the matrix are all so higher than that ofparent composite, the dislocation entwists each other intensively resulted in welding the composite successfully.

Diffusion welding of SiCp/2014Al composites using Ni as interlayer

SiCp/2014Al composites were bonded with the vacuum diffusion welding technique using Ni as the interlayer metal. Ni and Al were interdiffused and there were intermetallic compounds formed in the inter transition layer, which was composed of Ni3Al//NiAl//NiAl3. The relation between the diffusion distance and the element concentration was calculated according to Fick＇s second law. The relations of the diffusion concentration and the diffusion welding technique parameters were calculated.

Study on Non-interlayer Liquid Phase Diffusion Bonding for SiCp/ZL101 Aluminum Matrix Composite

Through the vacuum diffusion bonding for SiCp/ZLl01 aluminum matrix composite, the influence of bonding parameters on the joint properties was reported, with the aim to obtain optimal bonding parameters. The microstructureof joints was analyzed by means of optical microscope and scanning electron microscope in order to study the relationship between the macro-properties of joints and the microstructures. It was found that diffusion bonding couldbe used for bonding aluminum matrix composites successfully. Meanwhile, the properties of the matrix and the jointwere all affected by some defects such as the reinforcement aggregation in aluminum matrix composites made bystirring casting.

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.

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.

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.

Formation of interfacial Al-Ce-Cu-W amorphous layers in aluminum matrix composite through thermally driven solid-state amorphization

Interfacial Al-Ce-Cu-W amorphous layers formed through thermally driven solid-state amorphization within the(W+Ce O2)/2024 Al composite were investigated.The elemental distributions and interfacial microstructures were examined with an electron probe microanalyzer and a high-resolution transmission electron microscope,respectively.The consolidation of composites consisted of two thermal processes:vacuum degassing(VD)and hot isostatic pressing(HIP).During consolidation,not only the three major elements(Al,W,and Ce)but also the alloying elements(Mg and Cu)in the Al matrix contributed to amorphization.At VD and HIP temperatures of 723 K and763 K,interfacial amorphous layers were formed within the composite.Three diffusion processes were necessary for interfacial amorphization:(a)long-range diffusion of Mg from the Al matrix to the interfaces during VD;(b)long-range diffusion of Cu from the Al matrix to the interfaces during HIP;(c)short-range diffusion of W toward the Al matrix during HIP.The newly formed interfacial Al-Ce-Cu-W amorphous layers can be categorized under the Al-Ce-TM(TM:transition metals)amorphous system.

Non-isothermal aging behavior of in-situ AA2024−Al_(3)NiCu composite

The effect of non-isothermal aging treatment on microstructure and mechanical properties of in-situ AA2024−Al_(3)NiCu composite fabricated by the stir casting process was examined.The Al_(3)NiCu intermetallic was created by adding 3 wt.%nickel powder during stir casting and homogenization treatment at 500℃ for 24 h after casting.The microstructural results obtained using optical and scanning electron microscope indicate that,after non-isothermal aging treatment,the S-Al_(2)CuMg precipitates become finer,forming a poor zone of this precipitate in the area between the dendrites.Also,adding nickel during stir casting reduces the precipitation rate and the contribution of S-Al_(2)CuMg precipitates in strengthening composite during non-isothermal aging.The maximum hardness,ultimate tensile strength,and toughness achieved in the 3 wt.%nickel-containing sample after non-isothermal aging at 250℃ are(121.30±4.21)HV,(221.67±8.31)MPa,and(1.67±0.08)MJ/m^(3),respectively.The maximum hardness and ultimate tensile strength of AA2024−Al_(3)NiCu composite are decreased by 6%and 4%,respectively,compared to those of nickel-free AA2024 aluminum alloy.

Study on diffusion welding SiCp/ZL101 with Cu interlayer

Through the vacuum diffusion welding SiCp/ZL 101 aluminum with Cu interlayer,the effect of welding parameter and the thickness of Cu on the welded joint property wasinvestigated, and the optimal welding parameters were put forward at the same time. Themicrostructure of joint was analyzed by means of optical-microscope, scanning electron microscope inorder to study the relationship between the macro-properties of joint and the microstructure. Theresults show that diffusion welding with Cu interlayer could be used for welding aluminum matrixcomposites SiCp/ZL 101 successfully.

Diffusion welding SiC_p/ZL101 with Ni interlayer

Through the vacuum diffusion welding SiC_p/ZL101 aluminum with Ni interlayer,the effect of welding parameter and the thickness property of Ni on the welded joint wasinvestigated, and the optimal welding parameters were put forward at the same time. Themicrostructure of joint was analyzed by means of optical-microscope, scanning electron microscope(SEM) in order to study the relationship between the macro-properties of joint and themicrostructure. The results show that diffusion welding with Ni interlayer can be used for weldingaluminum matrix composites SiC_p/ZL101 successfully. Under the welding parameters T=560℃, P=5 MPa,t=60 min, H=14μm, the bonding strength of welded joint can up to 121 MPa. Moreover, the thicknessof interlayer should match with the size of reinforced particles. If the thickness of interlayer istoo thin, it would have no effect on the welded joint beneficially. If the thickness of interlayeris too thick, it would cause the 'no-reinforcement zone' to appear.

EFFECT OF OXIDATION OF SiC ON AGING CHARACTERISTICS OF SiC PARTICLES AND SHORT MULLITE FIBERS REINFORCED 2024Al COMPOSITE

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Aging behavior of AlNp/2024Al composites fabricated by squeeze casting

2024 aluminum matrix composites reinforced with different size AlN particles (0.5, 4 and 10μm) were fabricated by the squeeze-casting technology. The aging behavior and microstructure of AlNp/2024Al composites were investigated by Brinell hardness measurement and transmission electron microscopy (TEM). The results show that the precipitation sequence of AlNp/2024Al composites is similar to that of the matrix alloy aged at 160 and 190℃, but the age hardening rate of composites is improved, and the AlN particles with large size promote the precipitation process more obviously, in comparison with smaller AlN particles. With increasing temperature, the precipitation processes are accelerated, and the time to reach the peak hardness is shortened. The acceleration of the formation of GP region and phase S' in the composites is attributed to the interfaces (between particles and the matrix) and the high density of dislocations introduced by addition of AlN particles.

Effects of Mg content on aging behavior of sub-micron Al_2O_(3p)/Al-Cu-Mg composites

30%Al2O3p/Al-Cu-2.0Mg composite and Al2O3p/Al-Cu-2.5Mg composite with 0.3μm-Al2O3 particles were fabricated. Age-hardening behaviors of two composites and the related matrix alloys were studied by means of Brinell-hardness measurement, DSC and TEM. The results show that the hardness of the composite is improved obviously because of the addition of sub-micron Al2O3 particles. But the hardness increment of Al2O3p/Al composite after aging is lower than that of the related matrix alloy. Moreover, the formation of GP region is suppressed by the addition of sub-micron Al2O3 particles, which broadens the exothermic peak of S' phase. The increment of Mg content has a different influence on accelerating the aging processes of aluminum alloys and the composites, and the hardness also increases.

Two-stage aging treatment to accelerate aging kinetics without impairing strength in B_4C/7A04Al composite

Aging treatments are the key process to obtain satisfactory strength for 7xxxAl alloys and their composites. However, traditional single-stage(SS) aging is time-consuming to reach a peak strength condition. In this study, an efficient 120℃ + 160℃ two-stage(TS) aging treatment was proposed on a B_4C/7A04Al composite fabricated via powder metallurgy(PM) technology, which could acquire similar peak-aging strength but only took about 15% of the time compared to traditional 120℃ SS aging. The evolution of precipitation during the TS aging was investigated, as well as those of the 7A04Al alloys for comparison. In the second stage aging process, the higher aging temperature accelerated the nucleation of η′ phases inside the grains and thus increased the density of precipitates. Moreover, the short aging time limited the coarsening of precipitates and the broadening of precipitatefree zones. The above factors were beneficial for quickly obtaining satisfactory precipitation strengthening effects. The B_4C/7A04Al composite exhibited slower aging kinetics than the 7A04Al alloy in the TS aging. Mg elements consumption by the chemical reaction between B impurities introduced by B_4C particles and the Al matrix was considered to potentially retard the aging kinetics of the B_4C/7A04Al composite. Nevertheless, the precipitation sequence was not affected.

AGE STRENGTHENING OF DIFFUSION WELDED JOINT OF Al_2O_(3p)/6061Al COMPOSITE

Tensile strength of diffusion welded joint of aluminum matrix composite is very low due to its poor weld- ability.In this paper, solution and age treatments were conducted on the welded joint of Al2O3p/ 6061Al composite subjected to diffusion welding using Gleeble 1500 machine, and ensile strength and microstructure of welded joint aged at175℃ were measured and analyzed respectively, Results showed that aging precipitation of welded joint is promoted effectively because of redistribution of reinforcement and a few number of dislocations in the matrix of weld zone resulting from welding pressure,and hence tensile strength of welded joint is increased significantly after aging treatment.

Structural considerations in friction welding of hybrid Al_2O_3-reinforced aluminum composites

Comparative studies on the relationship between the welding parameters and joining efficiency in the friction welding of hybrid Al203-reinforced aluminum composites were conducted. Metal matrix composites （MMCs） with 37% （volume fraction） aluminum particle were joined by friction welding. The results show that the effects of the rotation speed on the reduction rate of particle size are greater than those of the upset pressure, and the area of the MMC weld zone decreases as the joining efficiency increases, while it is considered that the joining efficiency does not increase as the reduction rate of particle size decreases. During the macro-examination of the bonding interlace, a gray discolored region was observed on the bonding interface, and the center of the region was dark gray. After the micro-examination of the bonding interface, base metal made some second particulate formed by condensed alumina particulate but discoloration part distributed minute alumina particulate without second particulate. Consequently, it was also observed that rotational speed of 3 000 r/min and upset pressure of 63.6 MPa showed a very good.joint.