ã€China Aluminum Network】 7050 aluminum alloy is a kind of super hard aluminum alloy material that can be heat-treated and strengthened. It is easy to cast, has good formability and has good comprehensive performance. As the aluminum alloy arc welding welds often have holes, cracks, undercuts and other defects, especially for the strengthening of the heat treatment of ultra-high strength aluminum alloy, the arc weldability is worse, easily hot cracks, seriously hampered the 7050 aluminum The application of alloys in industry. Friction stir welding (FSW), as a new welding method with high efficiency, high quality, environmental protection and low cost, can be well welded to 7xxx series high strength aluminum alloy. This paper selects the 8mm 7050-T7451 aluminum alloy plate for single-pass butt joint friction welding experiments, and analyzes the microstructure and mechanical properties of the joint.
The welding test material is 8mm thick 7075-T7451 aluminum alloy, and the stirring head material is H13 hot die steel. The chemical etching solution was 15ml HCl+1mlHF+2.5mlHNO3+95mlH2O; the microstructure of the weld zone was observed under the microscope OptelicsTMS130; the tensile test was performed on the CSS-44100 electronic multifunctional tester; the hardness was measured on the HX-1000 microhardness tester measuring.
The continuous dynamic recrystallization of the weld nugget occurs to form small equiaxed grains; the heat affected zone is in an arc shape under the action of mechanical force and thermal cycle; the grain of the heat affected zone is coarsened. When the rotating speed is 375r/min and the welding speed is 100mm/min, the tensile strength of the joint is relatively high, which can reach 88.6% of the base metal. The distribution of weld hardness shows a “W†shape, and the smaller value basically appears at the transition between the heat-affected zone and heat-affected zone on the receding side.
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