Effect of doping Mg on the microstructure and mechanical behaviours of a novel Co-9Al-4.5W-4.5Mo-2Ta-0.02B alloy at room- and high-temperatures
Effect of doping Mg on the microstructure and mechanical behaviours of a novel Co-9Al-4.5W-4.5Mo-2Ta-0.02B alloy at room- and high-temperatures
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DOI：
10.1016/j.jallcom.2017.03.259
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发表时间：
2017-07
影响因子：
6.2
通讯作者：
Yi-Hui Guo;Fei Zhong;Youxing Yu;Shusuo Li;J. Sha
中科院分区：
文献类型：
--
作者：
Yi-Hui Guo;Fei Zhong;Youxing Yu;Shusuo Li;J. Sha
研究了新型镁 (Mg) 掺杂 Co-9Al-4.5W-4.5Mo-2Ta-0.02B 合金（掺杂 0.1、0.3、0.7 和 1.0 at.% Mg，以下分别称为 0.1Mg、0.3Mg、0.7Mg 和 1Mg 合金）在室温和高温下的微观结构和机械行为。所有在 800 °C 时效 50 小时的合金均由 Co 固溶体基体 (γ-CoSS) 和纳米级立方体 γ'-Co3(Al, W) 沉淀物组成。观察到 Mg 主要在晶界和 γ'-Co3(Al, W) 相处偏析。在0.7Mg和1Mg合金中，更多的Mg在晶界偏析降低了Σ1∼3型晶界的比例以及晶界排除杂质O的能力。随着Σ1∼3晶界的减少和O含量的增加，0.7Mg和1Mg合金在室温下以混合穿晶-间晶模式断裂，拉伸强度和延展性较低。然而，0.1和0.3Mg合金以穿晶模式断裂，具有更高的强度和延展性。这四种合金在 700°C 时表现出压流应力异常，并且当标称 Mg 含量在 600–800°C 增加到 0.7–1 at.% 时，强度明显下降。对于0.1Mg和0.3Mg合金，从室温到800°C的强度较高，并且不受标称Mg含量的明显影响，这主要是由于两种合金具有几乎相同且更高的Σ1∼3晶界分数以及晶界中较低的O浓度。
The microstructure and mechanical behaviour of a novel magnesium (Mg) doped Co-9Al-4.5W-4.5Mo-2Ta-0.02B alloy (doped 0.1, 0.3, 0.7 and 1.0 at.% Mg, referred to as 0.1Mg, 0.3Mg, 0.7Mg and 1Mg alloys hereafter, respectively) at room- and high- temperatures have been investigated. All alloys aged at 800 °C for 50 h consist of a Co solid-solution matrix (γ-CoSS) and nano-scale cuboidal γ′-Co3(Al, W) precipitates. Mg is observed to segregate primarily at the grain boundaries and the γ′-Co3(Al, W) phase. In the 0.7Mg and 1Mg alloys more Mg segregation at the grain boundaries decreases the fraction of Σ1∼3 type grain boundaries and the capability of excluding impurity O from the grain boundaries. With decreased Σ1∼3 boundaries and higher O content, the 0.7Mg and 1Mg alloys fracture in a mixed transgranular-intergranular mode at room temperature with lower strength and ductility under tension. However, the 0.1 and 0.3Mg alloys fracture in a transgranular mode with higher strength and ductility. The four alloys exhibit compressive flow stress anomalies at 700 °C and the strength obviously decreases when the nominal Mg contents increase to 0.7–1 at.% at 600–800 °C. As for the 0.1Mg and 0.3Mg alloys, the strengths from room temperature to 800 °C are higher and not obviously affected by the nominal Mg contents, primarily owing to the two alloys having almost the same and higher Σ1∼3 grain boundary fraction and the lower O concentration in the grain boundary.