Microstructure Characterization and Corrosion Resistance of TIG-Welded Al3Zr/A356 Composites

Abstract:

The Al₃Zr/A356 aluminum matrix composites (AMCs) with 3wt% reinforcing phase were prepared by in-situ reaction method. Through X-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, and microhardness tests, the microstructures and corrosion resistance of the welded joints after tungsten inert gas (TIG) welding with different welding parameters were investigated. Results show that when the welding current is 140 A, the formation of weld seam is optimal, and no welding defects, such as pores or cracks, appear. The fine Al₃Ti reinforcing particles are generated during the welding process, presenting the spherical and short rod shapes, and they are dispersed in the matrix. The hardness of the welded joint is higher than that of the base metal, and the strengthening effect of the reinforcing particles becomes obvious. With prolonging the immersion duration in 3.5wt% NaCl solution, the pitting degree of weld seam is aggravated, and the pitting mainly occurs around the grain boundaries and strengthening phases. The micro-area electrochemical experiment results show that when the welding current is 140 A, the corrosion potential fluctuation is small, the corrosion tendency is low, and the corrosion resistance is optimal.

Key words:aluminum matrix composites;TIG welding;in-situ reaction;corrosion resistance