BCC/B2难熔高熵高温合金中B2相的演化变质及其力学性能

IF 4.8 2区 材料科学 Q2 CHEMISTRY, PHYSICAL
Xiaofang Ma , Zhengfan Wang , Liang Chen , Peng Yang
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引用次数: 0

摘要

具有BCC/B2结构的难熔高熵高温合金(RHESAs),类似于ni基高温合金中的γ/γ′结构,由于其高熔点和优异的抗蠕变性能,被认为是超越ni基高温合金的有希望的候选者。然而,B2相固有的脆性和高温不稳定性限制了其实际应用。本研究的重点是Al9.26Nb17.92Ta18.4Ti43.47Zr10.95 (at。通过电弧熔炼制备RHESA,然后进行均匀化和不同时间的时效处理。采用透射电子显微镜(TEM)和室温压缩试验对时效过程中的相演化路径、元素扩散机制和力学性能变化进行了系统研究。结果表明:在固溶状态下,B2相以小于5 nm的纳米结构域存在,通过旋散分解和有序反应形成;经过5 ~ 60h的时效,B2相逐渐形成相互连接的网状结构。60h时效试样在不影响延性的情况下,强度增加了~ 25%。时效150 h后,B2相由拉长的前体向径向退化形成Al-Zr金属间化合物,并伴有Ti、Nb和Ta元素的析出。虽然强度和延性基本保持不变,但应变硬化率显著降低。本研究揭示了B2相的演化机理和Al-Zr金属间相的形成途径。利用透射电镜首次直接观察到B2相直接变质为Al-Zr金属间化合物的中间过程,同时在演化过程中发现了一种新的富ta立方相。为进一步优化RHEAs的高温稳定性提供了理论基础。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
The evolution and deterioration of the B2 phase and corresponding mechanical properties in the BCC/B2 refractory high-entropy superalloys
Refractory high-entropy superalloys (RHESAs) with a coherent BCC/B2 microstructure, analogous to the γ/γ′ structure in Ni-based superalloys, are regarded as promising candidates to surpass Ni-based superalloys due to their high melting points and exceptional creep resistance. However, the inherent brittleness and high-temperature instability of the B2 phase limit their practical application. This study focuses on the Al9.26Nb17.92Ta18.4Ti43.47Zr10.95 (at.%) RHESA prepared via arc melting, followed by homogenization and aging treatments for various durations. The phase evolution pathways, elemental diffusion mechanisms, and mechanical property changes during aging were systematically investigated using transmission electron microscopy (TEM) and room-temperature compression testing. The results demonstrate that in the ST (solution-treated) state, the B2 phase exists as nanodomains smaller than 5 nm, formed through spinodal decomposition and the ordering reaction. During aging for 5–60 h, the B2 phase grows into an interconnected network structure. The 60h-aged sample exhibits a ∼25 % increase in strength without compromising ductility. After 150 h of aging, the B2 phase degenerates radially from elongated precursors to form Al-Zr intermetallic compounds, accompanied by the expulsion of Ti, Nb and Ta element. While both strength and ductility remain largely unchanged, a significant reduction in the strain hardening rate is observed. This study reveals the evolution mechanism of the B2 phase and the formation pathway of the Al–Zr intermetallic phase. For the first time, the intermediate process of the direct deterioration of the B2 phase into the Al–Zr intermetallic compound was directly observed using TEM, and meanwhile, a novel Ta-rich cubic phase was identified during the evolution process. Those provides a theoretical foundation for further optimizing the high-temperature stability of RHEAs.
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来源期刊
Intermetallics
Intermetallics 工程技术-材料科学:综合
CiteScore
7.80
自引率
9.10%
发文量
291
审稿时长
37 days
期刊介绍: This journal is a platform for publishing innovative research and overviews for advancing our understanding of the structure, property, and functionality of complex metallic alloys, including intermetallics, metallic glasses, and high entropy alloys. The journal reports the science and engineering of metallic materials in the following aspects: Theories and experiments which address the relationship between property and structure in all length scales. Physical modeling and numerical simulations which provide a comprehensive understanding of experimental observations. Stimulated methodologies to characterize the structure and chemistry of materials that correlate the properties. Technological applications resulting from the understanding of property-structure relationship in materials. Novel and cutting-edge results warranting rapid communication. The journal also publishes special issues on selected topics and overviews by invitation only.
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