{"title":"Anomalous increase of fracture toughness of TiAl-based alloys at high temperature","authors":"","doi":"10.1016/j.matchar.2024.114215","DOIUrl":null,"url":null,"abstract":"<div><p>The anomalous increase of mechanical property of TiAl-based alloys at high temperature caters to the property requirements as the high-temperature structural materials, which is thus important and worth studying. However, people currently are not clear whether the fracture toughness of TiAl-based alloys has an anomalous increase at high temperature, and if so, how much it increases, and why it increases. In order to answer these questions, the forged Ti-44Al-8Nb model alloy with fine and uniform microstructure was used. The fracture toughness of the alloy at different temperatures was tested. The results indicated that the alloy did show an anomalous increase of fracture toughness at 700 °C–800 °C. The main crack deflected a large angle at 700 °C, and terminated at the upper part at 750 °C and 800 °C. The fracture morphology was fine, and the cleavage plane became smaller and less at high temperature. These characteristics corresponded to the anomalous increase of fracture toughness at high temperature. Through reverse thinking, we found that the high dislocation density was the root causing the anomalous increase of fracture toughness at high temperature. The forging-induced texture, such as <em>B2 〈100〉//RD</em> and <em>γ-TiAl 〈011]//RD</em> could also promote the dislocations slip on the main slip surfaces during the high temperature fracture toughness test, contributing to the final high dislocation density. The critical crack size at <em>700 °C–800 °C</em> was about 4 times that of room temperature, corresponding to the higher fracture toughness of the alloy at high temperature.</p></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":null,"pages":null},"PeriodicalIF":4.8000,"publicationDate":"2024-07-23","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/S1044580324005965","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
The anomalous increase of mechanical property of TiAl-based alloys at high temperature caters to the property requirements as the high-temperature structural materials, which is thus important and worth studying. However, people currently are not clear whether the fracture toughness of TiAl-based alloys has an anomalous increase at high temperature, and if so, how much it increases, and why it increases. In order to answer these questions, the forged Ti-44Al-8Nb model alloy with fine and uniform microstructure was used. The fracture toughness of the alloy at different temperatures was tested. The results indicated that the alloy did show an anomalous increase of fracture toughness at 700 °C–800 °C. The main crack deflected a large angle at 700 °C, and terminated at the upper part at 750 °C and 800 °C. The fracture morphology was fine, and the cleavage plane became smaller and less at high temperature. These characteristics corresponded to the anomalous increase of fracture toughness at high temperature. Through reverse thinking, we found that the high dislocation density was the root causing the anomalous increase of fracture toughness at high temperature. The forging-induced texture, such as B2 〈100〉//RD and γ-TiAl 〈011]//RD could also promote the dislocations slip on the main slip surfaces during the high temperature fracture toughness test, contributing to the final high dislocation density. The critical crack size at 700 °C–800 °C was about 4 times that of room temperature, corresponding to the higher fracture toughness of the alloy at high temperature.
TiAl基合金在高温下机械性能的异常增加,迎合了高温结构材料的性能要求,因此非常重要,值得研究。然而,目前人们还不清楚 TiAl 基合金的断裂韧性在高温下是否会出现异常增加,如果会,增加的幅度有多大,以及增加的原因是什么。为了回答这些问题,我们使用了具有精细均匀显微组织的锻造 Ti-44Al-8Nb 模型合金。测试了该合金在不同温度下的断裂韧性。结果表明,该合金在 700 ℃-800 ℃时的断裂韧性确实出现异常增长。主裂纹在 700 °C 时偏转角度较大,在 750 °C 和 800 °C 时终止于上部。高温时,断口形态细微,劈裂面变小且变少。这些特征与高温下断裂韧性的异常增加相对应。通过逆向思维,我们发现高位错密度是导致高温下断裂韧性异常增加的根本原因。在高温断裂韧性测试过程中,锻造引起的纹理(如和)也会促进位错在主滑移面上滑移,从而导致最终的高位错密度。高温下的临界裂纹尺寸约为室温下的 4 倍,这与合金在高温下更高的断裂韧性相对应。
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.