Alloy composition, deformation temperature, pressure and post-deformation annealing effects in severely deformed Ti-Ni based shape memory alloys
Alloy composition, deformation temperature, pressure and post-deformation annealing effects in severely deformed Ti-Ni based shape memory alloys
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DOI：
10.1016/j.actamat.2005.02.032
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发表时间：
2005-05-01
期刊：
影响因子：
9.4
通讯作者：
Prokofiev, EA
中科院分区：
文献类型：
--
作者：
Prokoshkin, SD;Khmelevskaya, IY;Prokofiev, EA
Ti-48.5, Ti-50.0, Ti-50.7 at的结构形成。% Ni和Ti-47 at。% Ni-3 at。采用透射电镜和x射线衍射方法研究了Fe形状记忆合金在高压扭转和变形后退火（200-400℃）条件下变形温度（-196 ~ 400℃）和压力（4- 8gpa）的变化规律。变形温度与马氏体起始温度（M-s）的相对值对非晶态组织形成的倾向有如下影响：初始马氏体合金的非晶态组织形成倾向最强，预马氏体奥氏体合金的非晶态组织形成倾向居中，初始热稳定奥氏体合金的非晶态组织形成倾向最弱。将变形温度降低到马氏体光洁度（M-f）以下，有利于非晶化。在奥氏体温度范围内提高变形温度可抑制非晶化。非时效Ti-Ni合金部分非晶化的极限变形温度在300℃左右，实际形成纳米晶组织的极限变形温度在350℃左右，时效Ti-Ni合金的极限变形温度略高于400℃。提出了等通道角挤压获得实际纳米晶结构的热力学条件。在Ti-48.5 at中观察到等温马氏体转变。% Ni合金由于在室温下保存10年之后，会发生严重的高温塑性变形。增加压力可以抑制非晶结构的形成。在覆盖纳米晶粒尺度的退火温度范围内，非晶结构经过变形后退火形成的纳米晶结构仍然比剧烈塑性变形形成的纳米结构精细。(c) 2005材料学报Elsevier Ltd.出版。版权所有。
Structure formation in Ti-48.5, Ti-50.0, Ti-50.7 at.% Ni and Ti-47 at.% Ni-3 at.% Fe shape memory alloys depending on deformation temperature (-196 to 400 degrees C and pressure (4-8 GPa) under conditions of high-pressure torsion and post-deformation annealing (200-400 degrees C) was studied using transmission electron microscopy and X-ray diffraction methods. The tendency to form an amorphous structure depends on the relative values of the deformation temperature and martensite start (M-s) temperature as follows: it is strongest in initially martensitic alloy, intermediate in a premartensitic austenite, and the weakest in initially thermally stable austenitic alloy. Lowering of the deformation temperature in the range below the martensite finish (M-f) temperature facilitates amorphization. Raising of the deformation temperature in the austenitic temperature range suppresses amorphization. The upper limiting deformation temperature for partial amorphization of the alloy having the highest M, is located about 300 degrees C. The upper limiting deformation temperature for actually nanocrystalline structure formation is located about 350 degrees C for non-aging Ti-Ni alloys and somewhat higher than 400 degrees C for aged Ti-Ni alloy. The thermomechanical conditions of the equal-channel angular pressing for obtaining actually nanocrystalline structure are recommended. Isothermal martensitic transformation is observed in the Ti-48.5 at.% Ni alloy as a result of keeping for 10 year at room temperature after high- temperature severe plastic deformation. Increasing the pressure suppresses the tendency to form an amorphous structure. The nanocrystalline structure formed under post-deformation annealing from the amorphous structure remains finer than the nanostructure formed as a result of severe plastic deformation through the annealing temperature range covering a nano-grain size scale. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.