| Magnesium alloys own the advantages of qualitative light, high strength and abundant mineral resources. However, its low toughness, poor corrosion resistance, which seriously restricts the advantages of light weight, high strength and pervasive application. If the surface of magnesium alloys alloys is covered with a layer of aluminium alloys, taking the advantage of high toughness and good corrosion resistance of aluminum alloys, which can improve the surface properties and comprehensive mechanical properties of magnesium alloys. In this paper, the aluminiun/magnesium alloys laminated composite material was fabricated by explosive welding. The formation and joint mechanism of composite interface are mainly studied.Because of the instantaneity and dangerousness of the process of explosive welding, it is difficult to capture on this process in detail. In this paper, aluminum alloys plate was clad layer and magnesium alloys plate was matrix. The ANSYS finite element simulation method is used to study the movement rule of composite material on bonding process and formation mechanism of interface, to discuss the formation process of wavy interface, the influencing factors of interface wave morphology and plastic flow mechanism of metal on the interface. Based on the results of numerical simulation, pratical explosive welding experiments were carried out. The morphology characteristic, the formation mechanism of vortex and local mechanics performance of interface bonding zone were studied by OM, SEM, EDS and Nano indentation test methods.Two-dimensional numerical simulation about the collision of aluminum/ magnesium alloys show that wavy joint interface is appeared. The velocity and pressure of material at the collision point reach the maximum. The peak pressure of Mg alloys and Al alloys can reach 8GPa and 2.2GPa, which are far more than the yield strength of material itself. The alternation of plus or minus about interface shear stress promptes the emergence of wave. In the process of collision, the peak value of effective plastic strain of Mg alloys and Al alloys are up to 4.0 and 1.1. The change trend of interface wave is consistent with effective strain on the interface.The movement rule of Al alloys and Mg alloys and propagation path of detonation shock wave were characterized by three-dimensional numerical simulation about the laminated composite of aluminum/magnesium alloys. The results show that Al alloys plate has experienced an accelerated process in the detonation. The velocity of Al alloys is less than 700m/s. The velocity of Mg allos plate which is perpendicular to the direction of detonation had experienced a leap from positive to negative. The maximum value were about 400m/s. The fluctuation with up and down of velocity also prompted the formation of wave. The cloud distribution of pressure and effective plastic strain on the surface of Al alloys plate present an arc shape and the detonation point is center.Based on the theory of stress wave propagation mechanism, a physical model about the formation of interface wave was established. It can be concluded that periodic interference and disturbance existed in the mutual interaction between tensile wave and compression wave. The metal with plastic fluid state moved to form wave under the disturbance of interference. In this paper, we obtained three kinds of interface topography under different conditions, which included flat, microwave and vortex. The wavelength and amplitude of microwave are about 1342μm and 274μm. The wavelength and amplitude of wave with vortex are about 2825μm and 677μm. The size of interface wave increases with the increase of quantity of explosive and spacing between base plate and flyer plate.Metal plastic flow mathematical model is established to explore the plastic flow mechanism of metal during the formation of interface wave. The state of metal particles near the collision point are active under the interference of stress wave. The Al alloys particles and Mg alloys particles with mutually embedded limited the range of those active particles. Therefore, the solid wave interface were formed. The formation time of a full waveform is about 0.2μs. The temperature on the interface can reach 1000 K in a moment. Then the metal on the interface may occur local metling. The liquid metal jetting will be captured by the flow of aluminum alloys, which forms vortex after solidification in front of wave crest.Taking 6061 Al with the thickness of 4mm as flyer plate, AZ31 B with the thickness of 20 mm as base plate, aluminum/magnesium alloys laminated composite materials were obtained by actual explosive welding. The composite interface presents wavy structure and combines together with mechanical lock. The thickness of diffusion layer is about 2.5μm. There are three zones, including melting zone, fine grain area and adiabatic shear band area at the side of the interface near the Mg alloys. Nano indentation test is used to analyse the microhardness of this three zones. The results show that the average microhardness of aluminum alloys and magnesium alloys are 1.29 GPa and 1.13 GPa, respectively. The average microhardness of adiabatic shear zone is 1.55 GPa, which is larger than that of fine grain area. And the average microhardness of fine grain aera is 1.51 GPa. The average microhardness of melting zone is up to 4.98 GPa. This shows that there were rigid internatallic compounds such as Al3Mg2, Mg17Al12 on the melting zone. Vortex is the larger melting block, which is forms in the front of wave crest. The organizations of vortex on the interface contain magnesium alloys substrate and intermediate phase Mg3Al2, Mg17Al12. The morphology of vortex obtained by experiment is similar with that of simulation results. |
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