Microstructural Evolution and Room Temperature Fracture Toughness of a Nb-Ti-Si-Cr-Al-Hf-Y Alloy Prepared by Directional Solidification

Abstract:

The Nb-24Ti-12Si-14Cr-2Al-2Hf-0.1Y (at.%) alloys were fabricated by directional solidification with selected withdrawal rate 1.2 and 18 mm/min, followed by a heat treatment at 1375 °C for 10 h. The microstructure of directional solidified samples were composed of Nb_SS, Cr₂Nb and eutectics (Nb_SS+Nb₅Si₃), aligning with the growth direction. After heat treatment, the Nb_SS in the eutectic structures and Nb_SS dendrites were connected to form the matrix, and the silicide and Cr₂Nb tended to spheroidize. The sample prepared by higher withdrawal rate plus heat treament shows higher average K_Q values. The results suggested that the Nb-Si based alloy showed higher room-temperature fracture toughness when the microstructure consists of continuous Nb_SS distributed with finer Nb₅Si₃ and Cr₂Nb.

• Periodical: Materials Science Forum (Volume 971)
• Pages: 59-64
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.971.59
• Online since: September 2019
• Authors: Guan Qun Zhuo, Lin Fen Su*, Kai Yong Jiang
• Keywords: Directional Solidification, Heat Treatment, Nb-Si Based Alloy, Room Temperature Fracture Toughness

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