{"title":"Phase transformation mechanism and microstructure of a Y-doped TiAl gas-atomized powders","authors":"","doi":"10.1016/j.matchar.2024.114520","DOIUrl":null,"url":null,"abstract":"<div><div>In this study, the phase transformation mechanism of a yttrium-containing β-solidified TiAl alloy (Ti-43Al-9 V-0.3Y at.%), prepared by gas atomization, was systematically investigated. X-ray diffraction, electron backscatter diffraction, scanning electron microscopy, and transmission electron microscopy were utilized to comprehensively analyze the morphology and microstructure of powders with varying sizes as well as the form and distribution of yttrium and its influence on the phase transformation of the powders. The results show that the solidification phase structure of the powders exhibits significant variations: the ultra-fine powder consists of α’ martensite and remaining β phase, while the medium-sized powder is solely composed of β<sub>0</sub> phase. The large-sized dendritic powder comprises β<sub>0</sub>, α’ martensite and α<sub>2</sub> phase. With an increase in powder size, there is a corresponding increase in the content of α<sub>2</sub> phase, whereas the content of martensite initially rises and subsequently declines. Additionally, yttrium is present in the form of multiscale Y-rich precipitates (YAl<sub>2</sub> and Y<sub>2</sub>O<sub>3</sub>) within the matrix, and the segregation degree gradually increases with increasing powder size. The primary factors contributing to the disparity in solidification structure include cooling rate and segregation defects. A faster cooling rate and a higher supercooling degree will inhibit the β → α transition, while the Y-rich precipitated phase forms a pre-existing strain zone around it, providing an effective site for martensitic nucleation. In summary, these findings offer novel insights into the mechanism of phase transformation in yttrium-containing β-solidified TiAl alloy, thereby contributing to further advancements in the theory of rapid solidification for TiAl alloys.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":null,"pages":null},"PeriodicalIF":4.8000,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Materials Characterization","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S104458032400901X","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, CHARACTERIZATION & TESTING","Score":null,"Total":0}
引用次数: 0
Abstract
In this study, the phase transformation mechanism of a yttrium-containing β-solidified TiAl alloy (Ti-43Al-9 V-0.3Y at.%), prepared by gas atomization, was systematically investigated. X-ray diffraction, electron backscatter diffraction, scanning electron microscopy, and transmission electron microscopy were utilized to comprehensively analyze the morphology and microstructure of powders with varying sizes as well as the form and distribution of yttrium and its influence on the phase transformation of the powders. The results show that the solidification phase structure of the powders exhibits significant variations: the ultra-fine powder consists of α’ martensite and remaining β phase, while the medium-sized powder is solely composed of β0 phase. The large-sized dendritic powder comprises β0, α’ martensite and α2 phase. With an increase in powder size, there is a corresponding increase in the content of α2 phase, whereas the content of martensite initially rises and subsequently declines. Additionally, yttrium is present in the form of multiscale Y-rich precipitates (YAl2 and Y2O3) within the matrix, and the segregation degree gradually increases with increasing powder size. The primary factors contributing to the disparity in solidification structure include cooling rate and segregation defects. A faster cooling rate and a higher supercooling degree will inhibit the β → α transition, while the Y-rich precipitated phase forms a pre-existing strain zone around it, providing an effective site for martensitic nucleation. In summary, these findings offer novel insights into the mechanism of phase transformation in yttrium-containing β-solidified TiAl alloy, thereby contributing to further advancements in the theory of rapid solidification for TiAl alloys.
本研究系统研究了通过气体雾化制备的含钇β固化 TiAl 合金(Ti-43-Al-9 V-0.3Y at.%)的相变机制。利用 X 射线衍射、电子反向散射衍射、扫描电子显微镜和透射电子显微镜全面分析了不同尺寸粉末的形态和微观结构,以及钇的形态和分布及其对粉末相变的影响。结果表明,粉末的凝固相结构表现出明显的差异:超细粉末由α'马氏体和剩余的β相组成,而中等尺寸的粉末则完全由β0相组成。大型树枝状粉末由 β0、α'马氏体和 α2 相组成。随着粉末粒度的增加,α2 相的含量也相应增加,而马氏体的含量最初上升,随后下降。此外,钇以多尺度富 Y 沉淀(YAl2 和 Y2O3)的形式存在于基体中,并且偏析度随着粉末尺寸的增大而逐渐增加。造成凝固结构差异的主要因素包括冷却速度和偏析缺陷。较快的冷却速度和较高的过冷度会抑制β→α转变,而富Y沉淀相则会在其周围形成一个预先存在的应变区,为马氏体成核提供一个有效的场所。总之,这些发现为含钇β凝固钛铝合金的相变机制提供了新的见解,从而有助于进一步推动钛铝合金快速凝固理论的发展。
期刊介绍:
Materials Characterization features original articles and state-of-the-art reviews on theoretical and practical aspects of the structure and behaviour of materials.
The Journal focuses on all characterization techniques, including all forms of microscopy (light, electron, acoustic, etc.,) and analysis (especially microanalysis and surface analytical techniques). Developments in both this wide range of techniques and their application to the quantification of the microstructure of materials are essential facets of the Journal.
The Journal provides the Materials Scientist/Engineer with up-to-date information on many types of materials with an underlying theme of explaining the behavior of materials using novel approaches. Materials covered by the journal include:
Metals & Alloys
Ceramics
Nanomaterials
Biomedical materials
Optical materials
Composites
Natural Materials.