Follow-up Method for Improving Al/cu Friction Stir Welding Seam Microstructure

Abstract

The invention discloses a method for improving a weld microstructure of Al / Cu friction stir welding in a follow-up manner. The method comprises the following steps: (1) adjusting the lowest working pressure, and adjusting the lowest pressing amounts of microstructure modification mechanisms; (2) adjusting the positions of the microstructure modification mechanisms by virtue of an adjustment-control mechanism, wherein two rolling wheels in a microstructure modification mechanism (II) with double rolling wheels correspond to the whole thermo-mechanical affected zone at an Al / Cu side as well as a part of a weld heat-affected zone and a part of a weld nugget zone; (3) starting up temperature control systems of the microstructure modification mechanisms, setting a modification temperature, setting a temperature T1 of the rolling wheels of a microstructure modification mechanism (I) to 290-315 DEG C, presetting a temperature T2 of the rolling wheels at an Al side of the microstructure modification mechanism (II) to 275-290 DEG C, setting a temperature T3 of the rolling wheels at a Cu side to 480-510 DEG C, heating the three rolling wheels to the modification temperature and then stopping heating; and (4) starting up a friction stir welding machine to start welding, enabling the microstructure modification mechanisms to start to work, and ensuring that the modification temperature set in the step (3) is achieved and stabilized until weld modification is ended during working by virtue of the temperature control systems of the microstructure modification mechanisms, wherein modification for the microstructure of the heat-affected zone can be realized after the end of the welding.

Description

technical field [0001] The invention relates to forging metallurgy technology, in particular to the technology of improving Al / Cu friction stir welding seam structure and improving mechanical properties. Background technique [0002] Friction stir welding is a patented welding technology invented by the British Welding Institute in 1991. It is widely used in the welding of dissimilar metals that are difficult to achieve by conventional fusion welding because of its small heat input, not easy to produce intermetallic compounds, and semi-solid welding. However, because the welding method is a semi-solid connection, when the melting points of dissimilar metals differ greatly, the weld is prone to defects, such as holes in the nugget area, tunnel defects, and microcracks in the mechanical heat-affected zone. [0003] Al / Cu dissimilar welding has extremely broad application prospects in the precious electrical industry, but in traditional fusion welding, due to the high welding t...

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Problems solved by technology

However, because the welding method is a semi-solid connection, when the melting points of dissimilar metals differ greatly, the weld is prone to defects, such as holes in the nugget area, tunnel defects, and microcracks in the mechanical heat-affected zone, etc.

[0003] Al / Cu dissimilar welding has extremely broad application prospects in the precious electrical industry, but in traditional fusion welding, due to the high welding temperature, a large number of hard and brittle intermetallic compounds are generated, resulting in extremely poor mechanical properties and low electrical conductivity. Affected; the heat input of friction stir welding is low, which greatly reduces the formation of intermetallic compounds, but due to the great difference in the melting point and thermal expansion coefficient of Al / Cu, the nugget area of ​​the weld shows holes and tunnels Defects, due to the accumulation, elongation, and growth of a large number of metal compounds in the mechanical heat-affected zone, the residual stress after welding is a tensile stress that is easy to break, and defects such as microcracks often appear

Mechanical properties and electrical conductivity are still limited

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