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Thermal stability of bimodal grain structure in a cobalt-based superalloy subjected to high-temperature exposure
Rare Metals ( IF 9.6 ) Pub Date : 2021-01-12 , DOI: 10.1007/s12598-020-01627-7
Cheng-Lin Li , Jeong Mok Oh , Seong-Woo Choi , Xin-Ming Mei , Jae-Keun Hong , Jong-Taek Yeom , Qing-Song Mei , Zhen-Tao Yu , Chan Hee Park

The present work investigates the thermal stability and mechanical properties of a Co–20Cr–15W–10Ni (wt%) alloy with a bimodal grain (BG) structure. The BG structure consisting of fine grains (FGs) and coarse grains (CGs) is thermally stable under high-temperature exposure treatments of 760 °C for 100 h and 870 °C for 100–1000 h. The size of both FGs and CGs remains no significant changes after thermal exposure treatments. The microstructural stability is associated with the slow kinetics of grain growth and the pinning of carbides. The thermal stability enables to maintain the BG structures, leading to the same mechanical properties as the sample without thermal exposure treatment. In particular, the BG alloy samples after thermal exposure treatment exhibit superior mechanical properties of both high strength and high ductility compared to the unimodal grain (UG) structured ones. The BG structure of the alloy samples after thermal exposure is capable of avoiding severe loss of ductility and retaining high strength. More specifically, the ductility of the BG alloy samples after thermal exposure treatments of 870 °C for 500–1000 h is ten times higher (44.6% vs. 3.5% and 52.6% vs. 5.0%) than that of the UG ones. The finding in the present work may give new insights into high-temperature applications of the Co–20Cr–15W–10Ni alloy and other metallic materials with a BG structure.

中文翻译:

高温暴露下钴基高温合金双峰晶粒结构的热稳定性

本工作研究了具有双峰晶粒 (BG) 结构的 Co-20Cr-15W-10Ni (wt%) 合金的热稳定性和机械性能。由细晶粒 (FG) 和粗晶粒 (CG) 组成的 BG 结构在 760°C 100 小时和 870°C 100-1000 小时的高温暴露处理下是热稳定的。FGs 和 CGs 的大小在热暴露处理后仍然没有显着变化。微观结构的稳定性与晶粒生长的缓慢动力学和碳化物的钉扎有关。热稳定性能够保持 BG 结构,导致与未经热暴露处理的样品相同的机械性能。特别是,与单峰晶粒 (UG) 结构的样品相比,经过热暴露处理的 BG 合金样品表现出优异的高强度和高延展性机械性能。热暴露后合金样品的BG结构能够避免延展性的严重损失并保持高强度。更具体地说,BG 合金样品在 870°C 热暴露处理 500-1000 小时后的延展性比 UG 高十倍(44.6% 对 3.5% 和 52.6% 对 5.0%)。目前工作中的发现可能为 Co-20Cr-15W-10Ni 合金和其他具有 BG 结构的金属材料的高温应用提供新的见解。热暴露后合金样品的BG结构能够避免延展性的严重损失并保持高强度。更具体地说,BG 合金样品在 870°C 热暴露处理 500-1000 小时后的延展性比 UG 高十倍(44.6% 对 3.5% 和 52.6% 对 5.0%)。目前工作中的发现可能为 Co-20Cr-15W-10Ni 合金和其他具有 BG 结构的金属材料的高温应用提供新的见解。热暴露后合金样品的BG结构能够避免延展性的严重损失并保持高强度。更具体地说,BG 合金样品在 870°C 热暴露处理 500-1000 小时后的延展性比 UG 高十倍(44.6% 对 3.5% 和 52.6% 对 5.0%)。目前工作中的发现可能为 Co-20Cr-15W-10Ni 合金和其他具有 BG 结构的金属材料的高温应用提供新的见解。
更新日期:2021-01-12
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