Yonghao Yu, Hongchao Kou, Tingting Zhao, Zilong Zhang, Yarong Wang, Xiaoxuan Xu, Peixuan Li, Mingxiang Zhu, Zhihong Wu, William Yi Wang, Jinshan Li
{"title":"Phase separation in hexagonal α phase during lamellar formation of TiAl alloys and its effect on subsequent phase transformations","authors":"Yonghao Yu, Hongchao Kou, Tingting Zhao, Zilong Zhang, Yarong Wang, Xiaoxuan Xu, Peixuan Li, Mingxiang Zhu, Zhihong Wu, William Yi Wang, Jinshan Li","doi":"10.1016/j.jmst.2024.10.013","DOIUrl":null,"url":null,"abstract":"TiAl alloys with the (α<sub>2</sub> + γ) lamellar structure are highly valued for their excellent high-temperature strength and creep resistance. Understanding the formation mechanism of the lamellar structure is crucial for tuning the microstructure and properties. This work investigates the formation of lamellar structure in Ti-48Al-7Nb-2.5V-1Cr alloy, revealing the presence of hcp-based long-period superstructure (hcp-LPS) as a metastable phase during lamellar formation. The identification of hcp-LPS demonstrates that the necessary solute enrichment for the formation of γ lamellae occurs on the hexagonal α matrix, implying that phase separation of α → Al-rich α lamellae + Al-depleted α lamellae is the first step of lamellar formation. Once phase separation is completed, all subsequent phase transitions occur within the Al-rich α lamellae. Additionally, the formation of twin lamellae is further discussed. The formation of the twin lamellae occurs sequentially. Pre-existing lamella promotes the formation of later lamella by inducing solute enrichment in its surrounding region, and then the successive slip of Shockley partial dislocations with opposite Burgers vectors ensures special stacking of later lamellae. These findings not only contribute to the fundamental understanding of spinodal mechanisms in hexagonal crystals, but also provide novel insights into the formation of twin lamellae.","PeriodicalId":16154,"journal":{"name":"Journal of Materials Science & Technology","volume":null,"pages":null},"PeriodicalIF":11.2000,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Materials Science & Technology","FirstCategoryId":"88","ListUrlMain":"https://doi.org/10.1016/j.jmst.2024.10.013","RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
TiAl alloys with the (α2 + γ) lamellar structure are highly valued for their excellent high-temperature strength and creep resistance. Understanding the formation mechanism of the lamellar structure is crucial for tuning the microstructure and properties. This work investigates the formation of lamellar structure in Ti-48Al-7Nb-2.5V-1Cr alloy, revealing the presence of hcp-based long-period superstructure (hcp-LPS) as a metastable phase during lamellar formation. The identification of hcp-LPS demonstrates that the necessary solute enrichment for the formation of γ lamellae occurs on the hexagonal α matrix, implying that phase separation of α → Al-rich α lamellae + Al-depleted α lamellae is the first step of lamellar formation. Once phase separation is completed, all subsequent phase transitions occur within the Al-rich α lamellae. Additionally, the formation of twin lamellae is further discussed. The formation of the twin lamellae occurs sequentially. Pre-existing lamella promotes the formation of later lamella by inducing solute enrichment in its surrounding region, and then the successive slip of Shockley partial dislocations with opposite Burgers vectors ensures special stacking of later lamellae. These findings not only contribute to the fundamental understanding of spinodal mechanisms in hexagonal crystals, but also provide novel insights into the formation of twin lamellae.
期刊介绍:
Journal of Materials Science & Technology strives to promote global collaboration in the field of materials science and technology. It primarily publishes original research papers, invited review articles, letters, research notes, and summaries of scientific achievements. The journal covers a wide range of materials science and technology topics, including metallic materials, inorganic nonmetallic materials, and composite materials.