Improvement of tensile behaviours of a γ'-Co3(Al, W) strengthened polycrystalline Co-9Al-4.5W-4.5Mo-2Ta-0.02B alloy at room-and high-temperatures by doping Ce

Publication date: Available online 11 September 2019Source: Progress in Natural Science: Materials InternationalAuthor(s): Zhuolin Tao, Fei Zhong, Youxing Yu, Jiangbo ShaAbstractThe microstructures and tensile behaviours of cerium (Ce) doped polycrystalline Co-9Al-4.5W-4.5Mo-2Ta-0.02B alloys (doped 0.05 and 0.2 at.% Ce) at room temperature (RT) and 600–800 °C were investigated. In-suit tensile test under SEM was conducted to understand the deformation and damage mechanisms at RT. Aged at 800 °C for 50 h, the 0.05Ce alloy consisted of a Co solid-solution matrix (γ-CoSS) and nano-scale cuboidal γ′-Co3(Al, W) precipitates, while for the 0.2Ce alloy, κ-Co3(W, Mo) precipitates and γ′-depleted zone were present at the grain boundaries in addition to the γ/γ′ microstructure. The 0.05Ce alloy exhibited flow stress anomalies at 700 °C. With higher Σ1∼3 boundary fraction and cleaned-up grain boundary, the 0.05Ce alloy always showed greater strength and elongation than the 0.2 Ce alloy with the grain boundary precipitates at temperatures up to 800 °C. Doped 0.05 at.% Ce made the Co-9Al-4.5W-4.5Mo-2Ta-0.02B alloy have an excellent elongation of 6.1% at 700 °C, owing to a mixed transgranular dimple plus intergranular cleavage fracture. The slip bands transferring through the low-angle grain boundary and slipping of the γ′-Co3(Al, W) in the 0.5Ce alloy resulted in excellent ductility of 20.4% at RT.Graphical abstract
Source: Progress in Natural Science: Materials International - Category: Materials Science Source Type: research