s2005_α钛的孪生变形及其塑性韧性的研究

西安理工大学

硕士学位论文

α钛的孪生变形及其塑性韧性的研究

姓名：刘翠萍

申请学位级别：硕士

专业：材料学

指导教师：井晓天

20050301

摘 要

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题目：α钛的孪生变形及其塑性韧性的研究∗

学 科：材料学

作 者：刘翠萍 作者（签名）：

指导导师：井晓天 教授 导师（签名）：

答辩日期：2005.3

摘 要

本文分别对Ti-2Al 、Ti-2Zr 、Ti-2Sn 、Ti-Mo 和TiC 颗粒增强钛基复合材料(TiC/Ti)进行了室温（293K ）和低温（77K ）下的静拉伸实验，系统地研究了Ti-2Zr 、Ti-2Sn 和TiC/Ti 在相应温度下的低周疲劳性能，最后选出在室温和低温下综合性能较优异的合金化α钛合金Ti-2Zr 和Ti-Mo 及TiC/Ti ，对其进行室温和低温冲击韧性实验。通过金相、扫描电子显微镜、透射电子显微镜等观察方法，结合数学分析途径，较系统地研究了五种α钛合金在室温和低温下的力学性能和变形机制，尤其是孪生机制，同时分析了温度、合金元素、第二相粒子、应变量等因素对孪生切变的影响规律。结果表明：

1)合金元素Al 、Zr 、Sn 、M o 有效地提高了室温和低温下α钛的静拉伸强度，但没有恶化其塑性，尤其添加了Mo 和Zr 后塑性优异，TiC 颗粒的存在明显地提高了TiC/Ti 的静拉伸强度，但低温塑性明显下降；在低温下,各材料仍有较高的疲劳寿命；Ti-2Zr 和Ti-Mo 经过冲击力的作用后，室温和低温冲击功变化微小，均体现为韧性特征，TiC/Ti 在低温下冲击功明显下降，转变为脆性特征。

2)在室温下,Ti-2Al 、Ti-2Zr 、Ti-2Sn 和Ti-Mo 均以位错变形机制为主，低温下其孪生切变相对活跃，尤其在Ti-2Zr 、Ti-Mo 中；在TiC/Ti 中室温、低温下位错机制均占主导地位；循环载荷激发了更多类型的孪晶。

3)合金元素对孪生切变的影响与材料的原始组织、固溶度、电负性、原子尺寸有关，其中Zr 、Sn 、Mo 影响较小；TiC 颗粒阻碍了基体钛中的孪生切变，与晶格结构、排列方式有关。

∗本研究得到国家自然科学基金（50201011）资助。

西安理工大学硕士学位论文

II 4)对TA2研究发现：低温下，随应变量增加，孪晶分数分阶段性逐渐增大，

且不同阶段产生不同的孪晶类型；形变孪晶的产生可能存在孕育期和极限变形量。关键字：α钛合金；变形机制；孪生；合金元素；TiC颗粒

Abstract

TOPIC: TWINNING DEFORMATION AND PLASTICITY AND TOUGHNESS OF α-TITANIUM ALLOYS∗Major: Material Science

Author: Liu Cuiping Signature：Supervisor: Pro. Jing Xiaotian Signature：

Reply Date：2005.03

Abstract

Tensile tests were carried out with Ti-2Al、Ti-2Zr、Ti-2Sn、Ti-Mo and TiC particle-reinforced titanium matrix composite(TiC/Ti) at RT(293K) and cryogenics (77K), respectively. And symmetrical push-pull low-cycle fatigue tests were systematically conducted with Ti-2Zr、Ti-2Sn and TiC/Ti . Then impact tests were performed with the most valuable Ti-2Zr and Ti-2Sn as well TiC/Ti. By metallography, SEM and TEM together with maths analysis, mechanical properties and deformation mechanisms of five α-titanium alloys at 293K and 77K were summarized and discussed, especially twinning mechanism and twinning influence factors . The results are as follows:

1)Al、Zr、Sn and Mo remarkably increase the strength of α-titanium alloys at 293K and 77K, but keep excellent plasticity, especially in Ti-2Zr and Ti-Mo; the plasticity of TiC/Ti decreases at 77K .Fatigue lifves of the three alloys are still high at 77K. From 293K to 77K, impact works of Ti-2Zr and Ti-Mo change little, and both show ductile characteristic. But TiC/Ti shows great decrease of impact work and changes to brittleness from 293K to 77K.

2) At 293K,dislocation slip is the dominant deformation mechanism in four alloying α-titanium alloys; at 77K, twinning becomes livelier and even is the main deformation mode in Ti-2Zr and Ti-Mo. However, slipping predominates in TiC/Ti, no

∗The research is supported by the National Natural Science Foundation of China (50201011).

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