Microstructures and Characterization of Ti6Al4V Alloy Friction Stir Alloyed with Cu and Al Powders
Abstract
Friction stir processing (FSP) has been used to prepare composite materials by admixing copper and aluminum powder blends with Cu/Al mass ratios 2:1, 1:1 and 1:2 into Ti6Al4V alloy matrix using a nickel superaloy FSP tool. Structural evolution of a stir zone material was studied as depended on the Cu/Al mass ratio and number of FSP passes. The content of α(α’)-Ti increased in all samples after the first FSP pass but then slowly reduced with the FSP pass number increased to 4. The inverse dependence of β-Ti content on the FSP pass number was demonstrated. Intermetallic compounds TixCuyAlz, TixAly and TixСuy were detected in the stir zone obtained by admixing 2:1, 1:1 and 1:2 powder blends. The maximum tensile strength in the range 1050-1200 MPa was achieved after 4-pass FSP on all samples with ~35% reduction of the ductility as compared to that of the as-received alloy. The stir zones also had increased microhardness numbers as measured across the stir zone section perpendicular to the FSP tool travel direction.