Effects of Nb Content on the Mechanical Alloying Behavior and Sintered Microstructure of Mo-Nb-Si-B Alloys

• Main Authors: Tao Yang, Xiping Guo
• Format: Article
• Language: English
• Published: MDPI AG 2019-06-01
• Series: Metals
• Subjects: Mo-Nb-Si-B alloy; mechanical alloying; sintering; phase constituent; Nb addition
• Online Access: https://www.mdpi.com/2075-4701/9/6/653

Different from conventional Mo-Si-B-based alloys consisting of Moss, Mo₃Si, and Mo₅SiB₂, Mo₃Si-free Mo-Si-B-based alloys (Moss+Mo₅Si₃+Mo₅SiB₂ or Moss+Mo₅SiB₂) show great potentials for more excellent oxidation resistance and elevated temperature strength. In the present work, alloying element Nb was added to Mo-12Si-10B (at.%)-based alloy to suppress the formation of the Mo₃Si phase. Mo-12Si-10B-xNb (x = 10, 20, 22, 24, 26, 28, 30, and 40) bulk alloys were fabricated using mechanical alloying followed by cold pressing and then sintering at 1773 K for 2 h. Effects of Nb content on the mechanical alloying behavior and then sintered microstructure were studied. The addition of Nb with an amount less than 30 at.% accelerated the mechanical alloying process, but 40 at.% Nb addition decreased the process due to excessive cold welding and high powder volume. For the sintered bulk alloy prepared from the mechanically alloyed powders milled for 30 h, a critical Nb content between 24 and 26 at.% was found to suppress Mo₃Si production and γNb₅Si₃ phase formed in the alloys with the addition of Nb content more than 26 at.%. Prolongation of a prior milling process could facilitate the suppression of Mo₃Si and delay the formation of niobium silicides.