Effect of process parameters on microstructure and properties of laser welded joints of aluminum/steel with Ni/Cu interlayer

The effects of laser parameters and interlayer material on the microstructure and properties of the welded joint between 6061 aluminum alloy and stainless steel were studied.The results show that the density and microstructure of the welded joint can be optimized by changing the laser power with 0.05 mm Cu foil and 0.1 mm Ni foil as interlayer.A large number of new Cu-Al binary phases were found near the aluminum alloy,which effectively inhibited the formation of the binary brittle phase of Fe-Al.The maximum shear force of 1350.96 N was obtained with laser power of 2200 W.The shear force of the welded joint increased to 1754.73 N when the thickness of the Cu foil thickness changed to 0.02 mm.

Corrosion behavior of aluminum/steel dissimilar metals friction stir welding joint

The corrosion performance of aluminum/steel contact and aluminum/steel FSW joint in 3.5 wt.%NaCl solution were analyzed using potentiostatic tests.The post-corrosion microstructure of the welding joint was characterized by optical microscope(OM),scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The results showed that the localized corrosion of FSW joint of Al/steel dissimilar metals mainly initiated at the interface transition zone(ITZ).Precipitation of intermetallic compounds(IMCs)and Fe-rich phase particles in ITZ accelerated the corrosion of the FSW joint.This phenomenon has been attributed to distinct corrosion potentials between IMCs and steel,aluminum base metal.The corrosion resistance sequence of IMCs in ITZ is Fe_(3)Al>FeAl>Fe_(2)Al_(5).

Graphene-reinforced aluminum matrix composites prepared by spark plasma sintering

Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering（SPS）. The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide（Al_4C_3） is not formed during SPS processing. Further addition of graphene（above 1wt%） results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.

Multichip on Aluminum Metal Plate Technology for High Power LED Packaging

Multichip on Ahnnintnn Metal Plate（MOAMP） technology with simple structure and low thermal resistance is developed for effective heat reratrval of Light Emitting Diode（LED） p-n junction and LED lighting module to have high reliability. The thermal resistance of LED modules was numerical and experimental. Thermal resistance from the jtnction to aluminten metal plate, considering input power of IFD module using MOAMP technology, is 3.02 K/W, 3.23 K/W for the measured and calculated, respectively. We expect that the reported MOAMP technology with low thermal resistance will be a promising solution for high power LED fighting modules.

A High-Fe Aluminum Matrix Welding Filler Metal for Hardfacing Aluminum-Silicon Alloys

A high Fe containing aluminum matrix filler metal for hardfacing aluminum silicon alloys has been developed by using iron,nickel,and silicon as the major strengthening elements,and by measuring mechanical properties,room temperature and high temperature wear tests,and microstructural analysis.The filler metal,which contains 3.0%-5.0% Fe and 11.0%-13.0% Si,exhibits an excellent weldability.The as cast and as welded microstructures for the filler metal are of uniformly distribution and its dispersed network of hard phase is enriched with Al Si Fe Ni.The filler metal shows high mechanical properties and wear resistance at both room temperature and high temperatures.The deposited metal has a better resistance to impact wear at 220℃ than that of substrate Al Si Mg Cu piston alloy;at room temperature,the deposited metal has an equivalent resistance to slide wear with lubrication as that of a hyper eutectic aluminum silicon alloy with 27% Si and 1% Ni.

In situ reaction mechanism of MgAlON in Al–Al2O3–MgO composites at 1700°C under flowing N2

The Al–AlO–MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M, M, and M, respectively, were prepared at 1700°C for 5 h under a flowing Natmosphere using the reaction sintering method. After sintering, the Al–AlO–MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen Mwas composed of MgO and MgAlO. Compared with specimen M, specimens Mand Mpossessed MgAlON, and its production increased with increasing aluminum addition. Under an Natmosphere, MgO, AlO, and Al in the matrix of specimens Mand Mreacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al–AlO–MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an Natmosphere, the partial pressure of oxygen is quite low; thus, when the Al–AlO–MgO composites were soaked at 580°C for an extended period, aluminum metal was transformed into AlN. With increasing temperature, AlOdiffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with AlOto form MgAlO. When the temperature was greater than(1640 ± 10)°C, AlN diffused into AlOand formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and Mg AlOat high temperatures because of their similar spinel structures.

Effect of Mg and Si on infiltration behavior of Al alloys pressureless infiltration into porous SiCp preforms

The effect of Mg and Si additon to Al matrix on infiltration kinetics and rates of Al alloys pressureless infiltration into porous SiCp preform was investigated by observing the change of infiltration distance with time as the Al alloys infiltrate into SiCp preforms at different temperatures.The results show that infiltration of SiCp preforms by Al melt is a thermal activation process and there is an incubation period before the infiltration becomes stable.With the increase of Mg content in the Al alloys from 0wt% to 8wt%,the infiltration will become much easier,the incubation period becomes shorter and the infiltration rate is faster,but these effects are not obvious when the Mg content is higher than 8wt%.As for Si addition to the Al alloys,it has no obvious effect on the incubation period,but the infiltration rate increases markedly with the increase of Si content from 0wt% to 12wt% and the rate has no obvious change when the content is bigger than 12wt%.The effect of Mg and Si on the incubation period is related to the infiltration mechanism of Al pressureless infiltration into SiCp preforms and their impact on the infiltration rate is a combined result from viscosity and surface tension of Al melt and SiC-Al wetting ability.

Modified Al negative electrode for stable high-capacity Al-Te batteries

Metal aluminum batteries(MABs)are considered potential large-scale energy storage devices because of their high energy density,resource abundance,low cost,safety,and environmental friendliness.Given their high electrical conductivity,high theoretical specific capacity,and high discharge potential,Te is considered a potential positive electrode material for MABs.Nonetheless,the critical issues induced by the chemical and electrochemical dissolution of tellurium and subsequent chemical precipitation on bare Al negative electrodes result in poor cycle stability and low discharge capacity of Al-Te batteries.Here an efficient TiB_(2)-based modified layer has been proposed to address bare Al electrodes(Al/TB).Consequently,the low-voltage hysteresis and long cycle life of the Al/TB negative electrode have been achieved.In addition,the electrochemical performance of the Al-Te battery based on the Al/TB negative electrode is dramatically improved.Furthermore,the modified separator technology is introduced to match with the as-designed Al/TB negative electrode.Therefore,the record-setting long-term cycle stability of up to 500 cycles has been achieved in the Al-Te battery.The facile strategy also opens a potential route for other high-energy density battery systems,such as Al-S and Al-Se batteries.

Interfacial Microstructure and Mechanical Properties of Al/Mg Butt Joints Made by MIG Welding Process with Zn-Cd Alloy as Interlayer

Butt joints between Mg alloy AZ31 B and pure Al 1 060 sheets were produced via metal inert gas welding process with Zn-Cd alloy foil. Crack-free Al/Mg butt joints between AZ31 B Mg alloy and pure Al 1060 sheets were obtained. Intermetallic compound layer 1 and layer 2 had formed in fusion zone/Mg alloy and the average thickness of the layer 1 was about 50 μm. The intermetallic compound layer 1 consisted of Al12Mg17 and Mg2Si phases while layer 2 consisted of Al12Mg17, Mg2Si and Mg Zn2 phases. The crack started from the IMC layer at the bottom of the joint and propagated along the brittle IMC layer, then expanded into weld metal during the SEM in situ tensile test. The highest tensile strength of the dissimilar metal butt joints could reach 46.8 MPa and the effect ofinterfacial IMC layer on mechanical property of the joint was discussed in detail in the present study.

Interfacial characteristics and properties of a low-clad-ratio AA4045/AA3003 cladding billet fabricated by semi-continuous casting

A low-clad-ratio AA4045/AA3003 cladding billet was fabricated using a semi-continuous casting process and was subsequently extruded indirectly into a cladding pipe. The temperature distribution near the interface was measured. The microstructures, elemental distribution, Vickers hardness around the bonding interface, and the interfacial shear strength were examined. The results showed that the interface temperature rebounded when AA4045 melt contacted the supporting layer. The two alloys bonded well, with few defects, via the diffusion of Si and Mn in the temperature range from 569℃ to 632℃. The mean shear strength of the bonding interface was 82.3 MPa, which was greater than that of AA3003（75.8 MPa）, indicating that the two alloys bonded with each other metallurgically via elemental interdiffusion. Moreover, no relative slip occurred between the two alloys during the extrusion process.

ADVANCED SYNTHESIS OF LIGHT METALS

The synthesis, processing and mechanical properties of the light metals, aluminum,magnesium and titanium Produced by advanced techniques are reviewed. Synthesis techniques to be addressed will include rapid solidification, spray deposition, mechanical alloying, plasma Processing and vapor deposition.

Turning of aluminum metal matrix composites： influence of the reinforcement and the cutting condition on the surface layer of the workpiece

Aluminum metal matrix composites （Al-MMCs） are difficult to machine. The reinforcement of aluminum using ceramic particles accelerates tool wear. Moreover, demanded machining accuracies or properties of the surface layer are difficult to achieve. In the present study, the effect of silicon carbide reinforcement particles on the surface layer of the workpiece was investigated using multiple cutting conditions for dry turning. Three differently reinforced Al-MMCs regarding the volume percent-age （17% and 30%） and the particle size （0.6 μm and 3 μm） and their non-reinforced matrix were considered as the workpiece materials. The reinforcement and the cutting condition affect the results of turning. A greater particle volume percent improves the surface roughness and decreases the tensile stress in the surface. The smaller particle size caused a lower tensile stress in the surface. A general effect of the particle size on the workpiece roughness can not be concluded. The most important cutting parameter for the surface layer of the workpiece is the feed. Greater feeds decrease the tensile stress in the surface, but deteriorate the surface quality.

Mold-Filling Ability of Aluminum Alloy Melt during the Two-Step Foaming Process

For the two-step foaming method, one of the most cost-effective ways to fabricate three-dimensional shaped aluminum alloy foams with dense outer surface skin, it is crucial to describe and predict the mold- filling behavior of the shaped aluminum alloy foams with a favorable pore-distribution accurately. In this paper, a mold-filling model for semi-solid aluminum alloy foams was initially established and subse- quently employed to predict the filling height, which represents the mold-filling ability of semi-solid aluminum alloy foams in a specially designed tube-like mold. Our results indicate that the proposed model can be applied to characterize the mold-filling property of aluminum alloy melts in a quantitative manner. Theoretically, our findings actually provide a guideline for mass-production of the shaped aluminum alloy foams by using the two-step foaming process,