Abstract
The laser hot-wire welding process was adopted to weld 7075 high-strength aluminum alloy. The influence laws of parameters on the weld formation were analyzed during laser hot-wire welding, and the microstructure characteristics and mechanical properties of welds were analyzed. The results showed that the parameters whose significance of influence on weld formation as ranked from high to low were laser power, current, gap width, welding speed and wire feeding rate. With the increase of wire temperature, the weld formation quality became better initially and then worse. Under the condition of optimized parameters, good weld formation could be obtained. The weld zone had a fine grain microstructure, and was in casting state consisted of dendritic crystal and equiaxed crystal. The heat affected zone mainly consisted of columnar crystal. The microhardness decreased gradually from base metal to heat affected zone then to weld zone. The tensile fracture of weld specimen occurred at the weld zone, and was in the ductile fracture state. The tensile strength of weld joint was 206 MPa and was 64.2% of base metal strength.
Highlights
High-strength aluminum alloy is widely used in high speed trains, aerospace, military industry and high-end equipment fields by virtue of its high strength, high corrosion resistance and other beneficial combination properties [1,2]
Laser welding of high-strength aluminum alloy has many advantages, such as a small heat affected zone, little welding deformation, high bonding strength, and high welding efficiency [5,6,7,8,9]. It has restrictions: (1) strict requirements applied to the butt joint gap of laser welding; (2) the welding process is unstable, the weld formation is unsatisfactory, and the collapse, pore, crack and other defects occur; (3) the weld elements are burnt and lost, and the weld performance is difficult to be regulated by controlling the element composition
The results showed that the preheating of wire and sufficient laser power can produce a fully penetrated keyhole, which could effectively improve the gap tolerance and inhibit oxidation
Summary
High-strength aluminum alloy is widely used in high speed trains, aerospace, military industry and high-end equipment fields by virtue of its high strength, high corrosion resistance and other beneficial combination properties [1,2]. The results showed that the hot wire reduced the laser energy consumption, and the feeding stability of the welding wire was controlled and good welding quality was obtained. If the heating temperature of welding wire was too low, the welding wire needed to absorb more laser energy to melt; if the heating temperature of welding wire was too high, the welding wire would lose its rigidity and be difficult to be accurately fed into the molten pool; only when the welding wire was at appropriate preheating temperature, would the transition of welding wire could be continuous and stable, and good weld formation would be obtained [26,27]. The influence laws of different parameters (including hot-wire current, laser power, welding speed, wire feeding rate and gap width) on the weld formation were investigated through the orthogonal experimental method. The microstructures and mechanical properties of welds were studied and discussed
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