Isochronal Phase Transformation in Bimodal Ti-55531
Isochronal Phase Transformation in Bimodal Ti-55531
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DOI：
10.3390/met9070790
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发表时间：
2019-07
期刊：
影响因子：
2.9
通讯作者：
Fuwen Chen;Guanglong Xu;K. Zhou;Hui Chang
中科院分区：
文献类型：
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作者：
Fuwen Chen;Guanglong Xu;K. Zhou;Hui Chang
在行业相关Ti-55531中，通常使用球状α和针状α相嵌入β基体中的双峰显微组织。为了通过热处理优化Ti-55531的性能，理解和控制所接收的双峰Ti-55531中的相变以及其微观结构演变是至关重要的。本文采用XRD、XRD相分析和SEM观察相结合的方法，系统研究了Ti-55531在连续加热过程中的等时相转变和显微组织演变。在678 K时，只有针状α发生β → α相变。当温度高于788 K时，α → β相变分两个阶段进行，α针状→ β和α球状→ β转变）。α球状体的溶解发生在α针状体溶解完成之后。由于α针状相和α球状相的化学成分和界面曲率的不同，α针状相→ β相的平均激活能低于α球状相→ β相的平均激活能。在本工作中的连续加热过程中的等时相转变和显微组织的演变可以用来优化热处理程序所需的机械性能。
Bimodal microstructures where globular α and acicular α phases are embedded in the β matrix are commonly used in industry-relevant Ti-55531. To optimize the performance of Ti-55531 through heat treatment, it is crucial to understand and control the phase transformation in the as-received bimodal Ti-55531 as well as its microstructure evolution. In this work, the isochronal phase transformations and microstructure evolution in the bimodal Ti-55531 during the continuous heating were systematically studied by combining dilatometry, XRD phase analyses, and SEM observation. The β → α transformation occurred at 678 K only with the acicular α. When the temperature was higher than 788 K, α → β transformation took place in two separate stages (i.e., αacicular → β and αglobular → β transformation). The dissolution of αglobular occurred after the dissolution of αacicular was completed. Due to the difference in the chemical composition and interface curvature between αacicular and αglobular, the average activation energy for αacicular → β transformation was lower than that for the αglobular → β transformation. The isochronal phase transformation and microstructure evolution during continuous heating in the present work could be used to optimize heat treatment procedures for desired mechanical properties.