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Density functional theory study of ω phase in steel with varied alloying elements
International Journal of Quantum Chemistry ( IF 2.3 ) Pub Date : 2020-03-26 , DOI: 10.1002/qua.26223
Assa Aravindh Sasikala Devi 1 , Sakari Pallaspuro 2 , Wei Cao 1 , Mahesh Somani 2 , Matti Alatalo 1 , Marko Huttula 1 , Jukka Kömi 2
Affiliation  

The presence of a long‐abandoned hexagonal omega (ω) phase in steel samples is recently gaining momentum owing to the advances in transmission electron microscopy (TEM) measurements, even though it is already reported in other transition‐metal alloys. The stabilization of this metastable phase is mainly investigated in presence of C, even though the formation of the ω phase is attributed to the combined effect of many factors, one among which is the enrichment of solute elements such as Al, Mn, Si, C, and Cr in the nanometer‐sized regimes. The present study investigates the effect of the above alloying elements in ω‐Fe using density functional theory (DFT) calculations. It is seen that the magnetic states of the atoms play a major role in the stability of ω‐Fe. Cohesive energy calculations show that the alloying elements affect the energetics and stabilization of ω‐Fe. Further, density of states calculations reveal the variation in dband occupancy in the presence of alloying elements, which in turn affects the cohesive energy. Phonon band structure calculations show that only ω‐Fe with substitutional C shows positive frequencies and hence possess thermodynamic stability. Finally, we confirm the existence of ω‐Fe using TEM measurements of a steel sample containing the same alloying elements. Our results can shed light on the stabilization of the ω in other transition‐metal alloys as well, in the presence of minor alloying elements.

中文翻译:

多种合金元素的钢中ω相的密度泛函理论研究

由于透射电子显微镜(TEM)测量的进展,钢样品中存在长被遗弃的六方欧米茄(ω)相近来正获得动力,尽管在其他过渡金属合金中已有报道。尽管ω相的形成归因于多种因素的综合作用,但主要还是在C的存在下研究了该亚稳相的稳定性,其中之一是Al,Mn,Si,C等溶质元素的富集。和Cr在纳米尺寸范围内。本研究使用密度泛函理论(DFT)计算研究了上述合金元素在ω -Fe中的作用。可以看出,原子的磁态在原子的稳定性中起主要作用。ω-铁 内聚能计算表明,合金元素会影响ω- Fe的能量和稳定性。此外,状态计算的密度揭示d的变化-在合金元素的存在,这反过来又影响内聚能带占用。声子能带结构计算表明,只有具有取代C的ω -Fe才显示正频率,因此具有热力学稳定性。最后,我们使用包含相同合金元素的钢样品的TEM测量来确定ω- Fe的存在。我们的研究结果还可以揭示在存在少量合金元素的情况下其他过渡金属合金中ω的稳定性。
更新日期:2020-03-26
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