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锻态TB6钛合金热变形行为研究及加工工艺参数优化

Study on Hot Deformation Behaviors and Optimization of Process Parameters for Titaniumalloy of Forging TB6

作者: 专业:材料加工工程 导师:王克鲁 年度:2010 学位:硕士  院校: 南昌航空大学

Keywords

TB6 titanium alloy, microstructure, deformation mechanism, processing map, process optimization

        TB6钛合金属于近β型钛合金,具有高强、高韧、高淬透性等特点,被广泛应用于航空、航天领域。该合金为难变形材料,其组织和性能对变形热力参数十分敏感,实际生产过程中不易保证获得组织和性能稳定一致的产品。本文对锻态TB6钛合金进行等温恒应变速率压缩试验,研究其热变形行为,并利用基于动态材料模型的加工图技术对该合金的热加工工艺参数进行了优化,研究结果对合理制定和优化TB6钛合金的热加工工艺参数具有重要的理论意义和实际应用价值。主要研究内容如下:对锻态TB6钛合金在Themecmater-Z热模拟机上对变形温度为8001150℃,应变速率为0.00110 s-1,最大压下量为60%的锻态TB6钛合金进行了等温恒应变速率压缩试验,并绘制出不同温度、不同应变速率下的真应力—真应变关系曲线。通过对曲线进行分析可以看出,流动应力对热变形过程中的温度和应变速率敏感性比较高,随着应变温度的升高和应变速率的降低,流动应力呈下降趋势。基于动态材料模型理论和Prasad判据,采用等温恒应变速率压缩试验数据,绘制出不同应变量下的锻态TB6钛合金的加工图。通过分析加工图并结合显微组织的观察,分析了锻态TB6失稳区的微观组织机理。结果表明:在变形温度为800875℃,应变速率范围为0.110s-1会出现绝热剪切和局部塑性流动;变形温度范围为8751150℃,应变速率范围为0.1810s-1会发生机械失稳。通过分析加工图,结合微观组织观察能够确定出比较适合的热加工工艺参数范围有三个,分别为:①变形温度为835880℃,应变速率为0.0010.01s-1;②变形温度为9751030℃,应变速率为0.00160.032s-1;③变形温度为11301150℃,应变速率为0.0010.0312 s-1,其变形机制为动态再结晶。
    Nearβ-titanium TB6 alloy of high-strength,good fatigue strength and excellent hardenability has been widely used in aviation and aerospace field.Titanium alloy TB6 is difficult-to-deform material,it’s microstructure and performance are sensitive to the thermomechnical parameters,which results in bad stability of microstructures and properties of forgings in actual manufacturing.In this paper,the hot deformation behaviors of the Titanium alloy of forging TB6 were first studied by using isothermal constant strain rate compression tests,and then the optimization of hot working parameters for this alloy were studied by using the processing map technology based on dynamic material model. The research results show the important theory significance and practical application value in determining and optimizing hot processing parameters.The following are major contents.Isothermal constant strain rate compression tests for Titanium alloy of forging TB6 had been carried out by the thermecmaster-Z hot process simulator with the rang of temperature from 800℃to 1150℃stain rate form 0.001s-1 to 10s-1 and the max reduction 60%.A group of stress-strain curveswere obtained through the compression tests. The flow stress is sensitive to deformation temperature and strain rate,decrease with increasing of deformation temperature and decreasing strain rate.Based on dynamic materials model(DMM) and Prasad criterion,the processing maps of titanium alloy of forging TB6 were finished at different strains with the date of hot compression tests. Combined with microstructure observation,microstructure mechanisms of TB6 titanium alloy in instability region were analyzed. The results showed that adiabatic shearing and flow localization behavior tend occurred at the rang of temperature from 800℃to 875℃and stain rate form 0.1s-1 to 10s-1,mechanical instability tend occurred at the rang of temperature from 875℃to 1150℃and stain rate form 0.18s-1 to 10s-1.Integrated processing maps and microstuctures observation show that the desired deformation thermomechanical parameters are in the rang of 835880℃and 0.0010.01s-1,9751030℃and 0.0010.0312s-1,11301150℃and 0.0010.0312s-1.The deformation mechanism is dynamic recrystallization.
        

锻态TB6钛合金热变形行为研究及加工工艺参数优化

摘要4-5
Abstract5
第1章 绪论8-25
    1.1 钛合金的概述8-12
        1.1.1 引言8-9
        1.1.2 钛合金的分类及特点9-10
        1.1.3 TB6钛合金简介10-12
    1.2 钛合金的热变形行为研究12-18
        1.2.1 材料热变形行为的研究方法12-13
        1.2.2 钛合金热变形行为的研究内容13-16
        1.2.3 钛合金热变形行为的研究现状16-18
    1.3 加工图理论与应用18-22
        1.3.1 热加工材料模型18-21
        1.3.2 加工图研究现状21-22
    1.4 研究目的意义和主要研究内容22-25
        1.4.1 研究目的与意义22-23
        1.4.2 主要研究内容23-25
第2章 TB6钛合金的热压缩试验及其力学行为研究25-42
    2.1 实验材料与制备25-26
    2.2 高温压缩试验方法26-27
        2.2.1 试验设备26
        2.2.2 实验方案26-27
        2.2.3 热变形显微组织观察27
    2.3 TB6钛合金的应力-应变曲线及其分析27-33
        2.3.1 变形温度对 TB6 钛合金流动应力的影响28-30
        2.3.2 应变速率对 TB6 钛合金流动应力的影响30-33
    2.4 TB6 钛合金的变形激活能33-40
    2.5 结论40-42
第3章 TB6 钛合金的热加工图研究42-58
    3.1 热加工图理论42-46
        3.1.1 动态材料模型42-44
        3.1.2 加工图中失稳和稳定区域的确定44-46
    3.2 TB6 钛合金加工图及其分析46-51
        3.2.1 加工图的建立46
        3.2.2 加工图的分析46-51
    3.3 TB6 钛合金微观组织验证及变形机制分析51-56
        3.3.1 功率耗散峰区组织验证及变形机制分析51-54
        3.3.2 失稳区组织验证54-56
    3.4 结论56-58
第4章 结论58-59
参考文献59-65
攻读硕士学位期间发表论文65-66
致谢66-67
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