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首页> 美国卫生研究院文献>Materials >Microstructures and Isothermal Oxidation of the Alumina Scale Forming Nb1.7Si2.4Ti2.4Al3Hf0.5 and Nb1.3Si2.4Ti2.4Al3.5Hf0.4 Alloys
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Microstructures and Isothermal Oxidation of the Alumina Scale Forming Nb1.7Si2.4Ti2.4Al3Hf0.5 and Nb1.3Si2.4Ti2.4Al3.5Hf0.4 Alloys

机译：形成Nb1.7Si2.4Ti2.4Al3Hf0.5和Nb1.3Si2.4Ti2.4Al3.5Hf0.4合金的氧化铝鳞的微观结构和等温氧化

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摘要

Nb–silicide based alloy will require some kind of coating system. Alumina forming alloys that are chemically compatible with the Nb–silicide based alloy substrate could be components of such systems. The intermetallic alloys Nb1.7Si2.4Ti2.4Al3Hf0.5 and Nb1.3Si2.4Ti2.4Al3.5Hf0.4 were studied in the cast, heat treated and isothermally oxidised conditions at 800 and 1200 °C to find out if they are alumina scale formers. The alloys were designed using the alloy design methodology NICE and were required (i) not to have stable solid solution phase in their microstructures; (ii) not to pest and (iii) to form alumina scale. Their microstructures consisted of silicides and aluminides. Both alloys satisfied (i) and (ii) and formed thin scales at 800 °C. At 1200 °C the former alloy suffered from internal oxidation and formed alumina intermixed with Ti rich oxide beneath a thick “layered” scale of mixed oxides that contained Ti and/or Al and/or Si. There was no internal oxidation in the latter alloy that formed a thin continuous well adhering α-Al2O3 scale that was able to repair itself during oxidation at 1200 °C. In both alloys there was severe macrosegregation of Si, which in Nb1.3Si2.4Ti2.4Al3.5Hf0.4 was almost double that in Nb1.7Si2.4Ti2.4Al3Hf0.5. The severe macrosegregation of Si contributed to the formation of a “layered” structure in the former alloy that was retained at 800 and 1200 °C. Both alloys met the “standard definition” of High Entropy Alloys (HEAs). Compared with the range of values of the parameters valence band (VEC), δ and Δχ of bcc solid solution plus intermetallic(s) HEAs, only the Δχ of the alloy Nb1.7Si2.4Ti2.4Al3Hf0.5 was within the range and the parameters VEC and δ of both alloys respectively were outside and within the corresponding ranges. The alloy Nb1.3Si2.4Ti2.4Al3.5Hf0.4 exhibited strong correlations between the parameters Δχ, δ and VEC, and the range of values of each parameter was wider compared with the alloy Nb1.7Si2.4Ti2.4Al3Hf0.5. There was a strong correlation only between the parameters Δχ and δ of the latter alloy that was similar to that of the former alloy.
机译：Nb-硅化物基合金将需要某种涂层系统。与基于Nb-硅化物的合金基底化学相容的氧化铝形成合金可能是此类系统的组成部分。 Nb1.7Si2.4Ti2.4Al3Hf0.5和Nb1.3Si2.4Ti2.4Al3.5Hf0.4金属间合金在800和1200°C的铸造，热处理和等温氧化条件下进行了研究，以确定它们是否为氧化铝鳞前者。使用合金设计方法NICE对合金进行设计，并且要求（i）在其微观结构中不具有稳定的固溶相； （ii）不有害生物和（iii）形成氧化铝水垢。它们的微结构由硅化物和铝化物组成。两种合金都满足（i）和（ii）的要求，并在800°C时形成了薄鳞片。在1200°C时，前一种合金遭受内部氧化，形成的氧化铝与富含Ti的氧化物混合在一起，形成了一层厚的“分层”的混合氧化物，其中含有Ti和/或Al和/或Si。在后一种合金中没有内部氧化，该合金形成了薄且连续的，良好粘附的α-Al2O3鳞片，能够在1200°C的氧化过程中自我修复。两种合金中均存在严重的Si宏观偏析，Nb1.3Si2.4Ti2.4Al3.5Hf 0.4 中的Si几乎是Nb 1.7 Si 2.4 中的两倍。 sub> Ti 2.4 Al 3 Hf 0.5 。 Si的严重宏观偏析导致在以前的合金中形成了“分层”结构，该结构保留在800和1200°C下。两种合金均符合高熵合金（HEA）的“标准定义”。与bcc固溶体加上金属间化合物HEA的参数价带（VEC），δ和Δχ的值范围相比，仅Nb 1.7 Si 2.4 < / sub> Ti 2.4 Al 3 Hf 0.5 在该范围内，两种合金的参数VEC和δ分别在相应范围之内和范围之内范围。合金Nb 1.3 Si 2.4 Ti 2.4 Al 3.5 Hf 0.4 表现出很强的相关性与合金Nb 1.7 Si 2.4 Ti 2.4 相比，参数Δχ，δ和VEC的分布范围更广，并且每个参数的取值范围更广Al 3 Hf 0.5 。仅后一种合金的参数Δχ和δ与前一种合金的参数之间存在很强的相关性。

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