Relationships of fracture toughness and dislocation mobility in intermetallics

Effects of B and Si on the fracture toughness of the Nb–Si alloys

“…The fracture toughness variation was also the result of composition variations, the fracture toughness of a-(Nb,Ti) 5 Si 3 increases with the increasing Ti, the K C peak occurs at about 20e32 at% Ti in a-(Nb,Ti) 5 Si 3 [11,12]. The composition of T2 is Nbe8.7Tie20.3Sie13.3B.…”

“…Chan utilized a microhardness indentation technique to initiate microcracks and determined the fracture toughness of individual silicides in the Nb-based in situ composites, which ranged from 3 to 12 MPa m 1/2 [11,12]. The fracture toughness variation was also the result of composition variations, the fracture toughness of a-(Nb,Ti) 5 Si 3 increases with the increasing Ti, the K C peak occurs at about 20e32 at% Ti in a-(Nb,Ti) 5 Si 3 [11,12].…”

Study of the role of Hf, Mo and W additions in the microstructure of Nb–20Si silicide based alloys

“…The aNb 5 Si 3 is the most stable phase (lowest formation energy) and the gNb 5 Si 3 the least stable one. The b and g forms exhibit high anisotropy in CTE (coefficient of thermal expansion) and moduli of elasticity E (Young modulus) and G (shear modulus) and the a form exhibits high strength at elevated temperatures and has nearly isotropic CTE and E, G. The unalloyed Nb 5 Si 3 has very low fracture toughness (<3 MPaOm [31]) that can be improved via alloying.…”

Fracture toughness and high temperature strength of unidirectionally solidified Nb–Si binary and Nb–Ti–Si ternary alloys

“…However, due to the catastrophic oxidation behavior of Nb-rich Nb-Si binary alloys at high temperatures [7], the recent studies on Nb-Si alloys have evolved into multicomponent systems to strike a balance between mechanical properties and environmental resistance [2,8,9]. The additions of Al and Cr lead to improved oxidation resistance [7,10], but increased DBTT of the (Nb) phase [11,12]. The additions of Mo and W enhance high temperature compressive strength of the alloys [13][14][15][16].…”