Microstructure and mechanical properties of large size as-cast Ti-43A1-9V-O.2Y (at.%) alloy ingot from brim to centre

摘要

A Ti-43A1-9V-0.2Y (at.%) alloy ingot with the size of $160 x 400 mm was prepared by vacuum arc remelting (VAR). The microstructure of the as-cast Ti-43A1-9V-0.2Y alloy was composed of B2/a2/Y lamellar colonies and massive B2 and y phases which were distributed along the boundaries of these lamellar colonies in the form of equiaxed grains. Based on the grain size variation along the radius direc tion of the ingot, the ingot could be divided into four ring regions from brim to centre. It has been under stood that the grain size variation between these four regions was due to the interplay of the effects of the cooling rate and the yttrium content on solidified microstructures in these regions. Mechanical testing of the samples cut from these four regions showed that there existed a clear correlation between the yield strength and the average grain sizes of the four ring regions, which approximately conformed to a Hall-Petch relationship.