Compressive Creep Behavior in Coarse Grained Polycrystals of Ti3Al and its Dependence on Binary Alloy Compositions

Abstract

ABSTRACTCompressive creep behavior has been investigated on coarse grained Ti3Al alloys with aluminum contents ranging from 15mol%Al to 42mol%Al, in order to obtain basic information concerning the chemical composition effect on creep of Ti3Al. Pure aluminum and titanium of 99.99% purity were arc-melted into small ingots weighing about 10grams under an argon atmosphere. The resulting microstructures after the hot deformation and vacuum annealing contained equiaxed grains whose average diameter ranged from 125 to 192 micrometers except alloys containing 40 and 42 mol% aluminum.Compressive creep tests were performed in vacuum on parallelepiped specimens with dimensions of 2mm×2mm×3mm. The applied compressive stress was 159MPa, and the test temperature was around 1200K.A very small primary transient and the minimum creep rate region followed by a gradual creep acceleration were observed in the materials containing aluminum up to 25mol%. In contrast to this, the materials containing more aluminum than 25mol% showed greater primary transient where creep deceleration continued up to about 0.1 true strain. Dual phase materials containing the γ phase showed small primary transient probably due to the constraint from the γ phase.