Effect of microstructure on mechanical properties in intermetallic compound Ti₃Al-Nb

Effect of microstructure on tensile properties and fracture toughness of Ti₃Al-Nb was investigated. The tensile properties and fracture toughness decrease with increase in the size of primary α₂. The tensile strength increases with decrease in the volume fraction of primary α₂ while the elongation and reduction of area decrease. The fracture toughness increases with decrease in the volume fraction of primary α₂ when the volume fraction of primary α₂ is between 8 and 17%. Decreasing cooling rate after solutionizing from water quenching to air cooling decreases tensile properties and fracture toughness in non-aged specimen because of the formation of transformed β during cooling. The tensile properties and fracture toughness decrease by aging because of the precipitation of α₂ when the cooling rate is greater like water quenching after solutionizing. The tensile strength, elongation, reduction of area and fracture toughness increase by aging when the cooling rate is smaller like air cooling after solutionizing because the transfored β is divided into smaller pieces although 0.2% proof stress decreases.