Abstract
The spray-formed 7055 aluminum alloy is welded by electron beam welding. Combined with the numerical simulation of a welding temperature field, the effect of different welding procedures on the microstructure and mechanical properties of welded joints is investigated in this study. Results show that the joints with good properties can be obtained under proper welding procedures. The microstructure analysis demonstrates that the fusion zone mainly consists of equiaxed grains, while a fine equiaxed grain zone is formed near the fusion line. There are mainly α(Al), MgZn2, Al2CuMg, and Mg32(Al,Zn)49 phases in the weld metal. The morphology of the weld can be improved by modification welding after the first bead welding, which is also advantageous to the mechanical properties of a welded joint. In the as-welded condition, compared with that of the base metal, the hardness of the weld zone decreased to a certain extent. The maximum tensile strength of a welded joint reaches 371.7 MPa. There are many dimples on the tensile fracture surface of a welded joint, and it dominantly presents the characteristic of ductile fracture. The simulated molten pool is consistent with the experimental weld morphology, and the reliability and accuracy of the simulation analysis are verified.
Highlights
With the rapid development of the aerospace industry, structural materials with high performance are increasingly required
The 7055 aluminum alloy belongs to the Al-Zn-Mg-Cu series; it has high tensile strength due to the strengthening phases such as η0 (MgZn2 ) and S(Al2 CuMg) precipitated in an
Peng et al [10] investigated the metal inert gas (MIG) welding of the 7020 aluminum alloy. Their results showed that the addition of a welding wire containing the element Zr was advantageous to the formation of β0 (Al3 Zr) particles in weldment; the β0 particles could effectively pin dislocations and inhibit recrystallization of base metal (BM), which was beneficial to the tensile strength of a welded joint
Summary
With the rapid development of the aerospace industry, structural materials with high performance are increasingly required. The 7000 series aluminum alloys have excellent comprehensive properties, such as low density, high tensile strength and high toughness, and good antifatigue and corrosion resistance [1,2]. They are widely used in many industry fields, such as aerospace, rail transportation, military equipment, etc. Peng et al [10] investigated the MIG welding of the 7020 aluminum alloy Their results showed that the addition of a welding wire containing the element Zr was advantageous to the formation of β0 (Al3 Zr) particles in weldment; the β0 particles could effectively pin dislocations and inhibit recrystallization of base metal (BM), which was beneficial to the tensile strength of a welded joint. Some results can be regarded as a guidance for the welding of the 7000 series aluminum alloys in the engineering application
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