Effect of boron addition on thermal and mechanical properties of Co-Cr-Mo-C-(B) glass-forming alloys. (August 2018)

• Record Type: Journal Article
• Authors: Kim, Jeong Tae; Hong, Sung Hwan; Bian, Xilei; Gokuldoss, Prashanth Konda; Song, Kaikai; Eckert, Jürgen; Park, Jin Man; Kim, Ki Buem
• Is Part Of: Intermetallics. Volume 99(2018:Aug.)
• Page Start: 1
• Page End: 7
• Publication Date: 2018-08
• Subjects: Metallic glasses -- Thermal stability -- Thermal properties -- Mechanical properties -- Casting -- Microstructure; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2018.05.006
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: In this work, we investigated the effect of boron addition on glass-forming ability and mechanical properties of Co-Cr-Mo-C alloys. The starting alloy was (Co0.65 Cr0.13 Mo0.22 )80 C20 derived from the Co65 Cr13 Mo22 ternary eutectic composition. This alloy is almost fully crystalline and exhibits brittle mechanical properties. Replacing carbon with boron allows obtaining bulk metallic glasses (BMGs) and bulk metallic glass composites. The designed alloys show very high strength (∼4100 MPa), wide super-cooled liquid region (∼100 K) and large endothermic enthalpy of the supercooled liquid region (∼35 J/g), indicating high thermal stability. The electronegativity difference and supercooled liquid region of the present alloys are comparable to rare-earth elements containing BMGs. The physical properties of the present alloys corresponded well with the alloy design strategy based on the unified parameter using the glass transition temperature, fracture strength, and molar volume. Furthermore, we propose the optimum compositional condition for glass formation by controlling the carbon-to-boron ratio and the influence of carbon on phase formation in this alloy system is discussed. Highlights: Effect of boron/carbon ratio on the glass formation, fracture strength, and thermal stability of Co-Cr-Mo eutectic alloy. The wide supercooled liquid region of 100 K when carbon to boron ratio is 2:1. The excellent thermal stability of supercooled liquid can offer a wide enough processing window for thermoplastic forming. The electronegativity difference is an indicator dominating the extension of the supercooled liquid region.