EFFECT OF TERNARY ALLOYING ELEMENTS ON MICROSTRUCTURE AND MECHANICAL PROPERTY OF Nb-Si BASED REFRACTORY INTERMETALLIC ALLOY

초록

Microstructure and mechanical property at room temperature and at 1773 K of Nb-Si based refractory intermetallic alloys were investigated in terms of compression and fracture toughness test. Mo and V were chosen as ternary alloying elements because of their high melting point, smaller atomic size than Nb. It was found that both ternary alloying elements have a significant role to modify the microstructure from dispersed structure to maze-like structure in Nb solid solution/Nb5Si3 intermetallic composites. 0.2% offset yield strength at room temperature increased with increasing content of ternary elements in Nb solid solution and volume fraction of Nb5Si3. At 1773 K, Mo addition has a positive role to increase yield strength, on the contrary V addition has a role to decrease yield strength. Fracture toughness of ternary alloys was superior to the binary alloys. Details will be discussed in correlation with ternary alloying, volume fraction of constituent phase and microstructure.