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Mechanically driven phase transformation in titanium and Ti alloys at high pressure torsion

高压扭转下钛和钛合金的机械驱动相变

基本信息

批准号：
267921614
负责人：
Privatdozentin Dr. Olga Fabrichnaya, Ph.D.
金额：
--
依托单位：
Institut für Werkstoffwissenschaft
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/267921614?language=en
关键词：
Mechanically driven phase transformation titanium

项目摘要

Severe plastic deformation (SPD) is increasingly intensively used for processing of nanostructured titanium and Ti-based alloys, at least on the laboratory scale. However, the SPD process does not only refine the microstructure, but it also initiates concomitant phase transformations. Depending on the experimental technique and on the pressure environment used, the phase transition of α-Ti to the high-pressure ω-Ti occurs between 2 and 12 GPa. Furthermore, external shear stresses can provide an additional driving force for martensitic phase transformation. In this respect, the application of SPD by high pressure torsion (HPT) is advantageous for studies of the α-Ti to ω-Ti transition, because this technique applies high pressure and shear strain simultaneously, and under well-controlled conditions. During the first funding period it was revealed that the HPT-induced phase transitions in Ti alloys depends on the amount alloying elements, especially of the elements stabilizing high-temperature β-Ti.The aim of this project is to investigate mechanically driven phase transformations in the Ti–Fe and Ti–Co alloys that were induced by HPT at elevated and cryogenic temperatures, in order to be able to describe the interplay between the diffusion processes and the martensitic (diffusionless) mechanism during the α → ω and β → ω phase transformations. Based on the results of the first funding period, we want to describe the effect of the microstructural features, in particular the effect of microstructure defects, on the stability of metastable phases, and to explain the relationship between the nanoscale structure achieved (local phase composition, nature of the grain and phase boundaries) and the resulting mechanical properties. Finally, a way for describing the stability of the metastable phases by using the CalPhaD method should be found. The microstructure and phase composition of the samples and the thermal stability of individual phases will be determined by using XRD (including in situ XRD at high temperatures), DSC, SEM, conventional and analytic TEM (including ACOM TEM), and Atom Probe Tomography. The influence of the initial state of the material (alloying, phase composition and microstructural features) and processing parameters (pressure, temperature, strain and strain rate) on the phase transformations will be evaluated. The experimental work will be complemented by the calculations of the high pressure phase diagrams. The proposed investigations will contribute to the basic knowledge regarding the mechanically driven phase transitions in Ti-based alloys. The obtained results will be important not only for fundamental materials science, but they will also allow to elaborate the principles of the thermo-mechanical treatments of ultrafine grained materials providing the high level of strength and ductility.

严重塑性变形 (SPD) 越来越多地用于纳米结构钛和钛基合金的加工，至少在实验室规模上如此。然而，SPD 过程不仅细化微观结构，而且还引发伴随的相变。根据实验技术和所使用的压力环境，α-Ti 到高压 ω-Ti 的相变发生在 2 至 12 GPa 之间。此外，外部剪切应力可以为马氏体相变提供额外的驱动力。在这方面，通过高压扭转（HPT）应用SPD对于研究α-Ti到ω-Ti转变是有利的，因为该技术在良好控制的条件下同时施加高压和剪切应变。在第一个资助期间，人们发现钛合金中 HPT 诱导的相变取决于合金元素的量，特别是稳定高温 β-Ti 的元素。该项目的目的是研究在高温和低温下 HPT 诱导的 Ti-Fe 和 Ti-Co 合金中机械驱动的相变，以便能够描述合金元素之间的相互作用。 α→ω 和 β→ω 相变过程中的扩散过程和马氏体（无扩散）机制。基于第一个资助期的结果，我们想要描述微观结构特征的影响，特别是微观结构缺陷对亚稳相稳定性的影响，并解释所实现的纳米级结构（局部相组成、晶粒和相边界的性质）与由此产生的机械性能之间的关系。最后，应该找到一种使用 CalPhaD 方法来描述亚稳态相稳定性的方法。样品的微观结构和相组成以及各个相的热稳定性将通过使用 XRD（包括高温下的原位 XRD）、DSC、SEM、常规和分析 TEM（包括 ACOM TEM）以及原子探针断层扫描来确定。将评估材料的初始状态（合金化、相组成和微观结构特征）和加工参数（压力、温度、应变和应变速率）对相变的影响。高压相图的计算将补充实验工作。拟议的研究将有助于了解有关钛基合金机械驱动相变的基础知识。所获得的结果不仅对基础材料科学很重要，而且还可以详细阐述超细晶粒材料的热机械处理原理，从而提供高水平的强度和延展性。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Formation of the ω Phase in the Titanium—Iron System under Shear Deformation

剪切变形下钛铁体系中Ï相的形成

DOI：
10.1134/s0021364020100033
发表时间：
2020
期刊：
JETP Letters
影响因子：
1.3
作者：
B.B. Straumal;A.R. Kilmametov;A.A. Mazilkin;A.S. Gornakova;O.B. Fabrichnaya;M.J. Kriegel;D. Rafaja;M.F. Bulatov;A.N. Nekrasov;B. Baretzky
通讯作者：
B. Baretzky

Formation and Thermal Stability of ω-Ti(Fe) in α-Phase-Based Ti(Fe) Alloys