The Microhardness and Microstrructural Changes of Mechanically Affected Zone by Cold Pressure Welding in Aluminum Rod

摘要

Microhardness, electrical resistivity and microstructures of a mechanically affected zone (MAZ) by cold pressure welding of aluminum rods in terms of joint pressures and the number of strokes were investigated in this study. The MAZ was defined as the area where the materials have been subjected to deformation generating hardening of the joint area. The macroscopic image of the MAZ also reveals that the horizontally aligned lamellar structure of material flowing due to a wire drawing process gradually began to form in a vertical direction while joint pressure was applied. Vickers microhardness tests inside the MAZ showed that higher hardness was obtained in the MAZ, and the highest value was achieved at the center of that area. Similar to the microhardness results, electrical resistivity was also enhanced in the MAZ, compared to the base Al rod. TEM analysis of the MAZ concluded that the extensive elongated subgrains bounded by microbands as expected from a high stacking fault energy metal like aluminum and many dislocations were formed inside the grains as well. Therefore, the behavior of microhardness and electrical resistivity are completely attributed to the change of microstructures.