Effect of friction stir processing on microstructures and mechanical properties of TIG cladding layer on AA7075

Abstract

AA7075 is a precipitation strengthened Al-Zn-Mg-Cu alloy which has been widely used. As a common way to repair AA7075 components, tungsten inert gas (TIG) cladding generates coarse grains and defects. In addition, the use of other types of filler wires could lead to insufficient rigidity and strength of the cladding layer. In the present work, friction stir processing (FSP) has been applied to the TIG cladding layer on AA7075 to study the effect of process parameters on microstructures and mechanical properties. The macro/micro structural characteristics, elemental distribution, microhardness distribution and tensile properties have been investigated. The macroscopic defects in TIG cladding layer are eliminated and the size of grains is decreases to around 6 μm by FSP. FSP reduces the compositional difference between the stir zone and the base material. Higher rotational speed promotes the grain refinement while the lower traverse speed benefits the microstructural uniformity. FSP on the TIG weld bead brings improvement in tensile properties and hardness. All the fractures for TIG+FSP samples occur at thermo-mechanically affected zone of the advancing side. The tensile strength of the stir zone increases from 424.2 to 442.8 MPa with the increase in rotational speed and traverse speed.

Investigation on the influence of FSP parameters on TIG welded dissimilar aluminum joints using RSM and desirability function approach

“…They observed that after FSP, there was substantial grain refinement with uniform distribution of intermetallic phases in the fusion region, resulting in a significant enhancement in weld corrosion resistance. Shi et al 24 explored the FSP to the TIG cladded layer on AA7075-T6-T6 alloys with filler ER5356 and examined its effect on microstructure, elemental distribution and mechanical properties. They concluded that following FSP, the macroscopic defects were reduced and fine grains were seen in the cladded zone, which increased the tensile and microhardness strengths.…”