Microstructure-Property Relationship in Low Cost Powder Processed Ti1Al8V5Fe Alloy

Ti1Al8V5Fe (Ti185) billets 90 mm in diameter and 1300 mm were produced using the low cost powder metallurgy process that relies on using TiH₂ as a feedstock material. These billets were rolled in the beta phase field to form 16 mm diameter bars and were later subjected to solution heat treatment and aging (STA) in the alpha-beta phase field. All the samples were aged at 482°C for 2 hrs. Tensile tests and rotating beam fatigue tests were conducted to evaluate the mechanical properties as a function of solution heat treatment. As the solution treatment temperature increased the yield and ultimate strength of the material increased proportionally. Detailed microstructural characterization using transmission electron microscopy (TEM) and atom probe tomography (APT) were utilized to study the STA samples to correlate the microstructure with the mechanical properties.  TEM and APT results provided evidence of two generations of intragranular alpha phase precipitation and a direct correlation of the morphology and distribution of intragranular alpha phase with the solution treatment temperature. A dense uniform distribution of fine scale alpha precipitation obtained by the highest temperature solution treatment was observed to correlate with the highest yield and ultimate tensile strength of the alloy.