TC11/Ti-22Al-25Nb双合金的热变形行为

在温度为900-1060℃和应变速率为0.001-10s^-1的条件下,通过热模拟压缩实验研究TC11/Ti-22Al-25Nb双合金电子束焊接件的高温热变形行为。结合实验数据,建立双合金热变形中流变应力随应变速率和变形温度的本构方程。同时对变形过程中的激活能进行计算和分析得出,激活能随着应变的增加而逐渐减小。在应变为0.9时激活能为334kJ/mol。变形过程中耗散率η随着变形参数的变化而变化;当应变速率为0.01、0.1和1s^-1时,η随应变的增加而增加;而当应变速率为0.001和10 s^-1时,η随应变的增加而减小。通过热加工图分析可知,最大耗散率（η=0.51）出现在1060℃和0...

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Published in中国有色金属学报：英文版 Vol. 25; no. 7; pp. 2195 - 2205
Main Author 秦春 姚泽坤 宁永权 石志峰 郭鸿镇
Format Journal Article
LanguageEnglish
Published 2015
Subjects
加工图
双合金
显微组织
激活能
热变形
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Summary:在温度为900-1060℃和应变速率为0.001-10s^-1的条件下,通过热模拟压缩实验研究TC11/Ti-22Al-25Nb双合金电子束焊接件的高温热变形行为。结合实验数据,建立双合金热变形中流变应力随应变速率和变形温度的本构方程。同时对变形过程中的激活能进行计算和分析得出,激活能随着应变的增加而逐渐减小。在应变为0.9时激活能为334kJ/mol。变形过程中耗散率η随着变形参数的变化而变化;当应变速率为0.01、0.1和1s^-1时,η随应变的增加而增加;而当应变速率为0.001和10 s^-1时,η随应变的增加而减小。通过热加工图分析可知,最大耗散率（η=0.51）出现在1060℃和0.1 s^-1,在此条件下,可以从焊缝区域组织中观察到明显的动态再结晶现象。而当应变速率降低时,耗散率η急剧下降,在1060℃和0.001s^-1的变形条件下,η降低到0.02,变形机制以动态回复为主。当失稳系数ξ（ε）为负时,材料高温变形发生失稳。分析可知,应变速率为0.001-0.6s^-1,变形温度为900-1060℃是双合金热变形的安全区域。
Bibliography:The high-temperature flow behavior of TCll/Ti-22Al-25 Nb electron beam（EB） weldments was investigated by the isothermal compression tests at the temperature of 900-1060℃ and the strain rate of 0.001-10 s-（-1）.Based on the experimental data,the constitutive equation that describes the flow stress as a function of strain rate and deformation temperature is obtained.The apparent activation energy of deformation is calculated,which decreases with increasing the strain and the value is 334 kJ/mol at strain of 0.90.The efficiency of power dissipation η changes obviously with the variation of deformation conditions.Under the strain rates of 0.01,0.1 and 1 s-（-1）,the value of η increases with increasing the true strain for different deformation temperatures.While the value of η decreases with increasing the strain under the strain rates of 0.001 and 10 s-（-1）.The optimum processing condition is（t（opi）=1060℃,ε（opi）=0.1 s-（-1）） with the peak efficiency of 0.51.Under this deformation,dynamic recrystallization（DRX） is observed obviously in the microstructure of welding zone.Under the condition of 1060℃ and 0.001 s-（-1）,the deformation mechanism is dominated by dynamic recovery（DRV） and the value of η decreases sharply（η=0.02）.The flow instability is predicted to occur since the instability parameter ξ（ε）becomes negative.The hot working process can be carried out safely in the domain with the strain rate of 0.001-0.6 s-（-1） and the temperature of 900-1060℃.
Chun QIN,Ze-kun YAO,Yong-quan NING,Zhi-feng SHI,Hong-zhen GUO（ School of Materials Science and Engineering, Northwestern Polytechnical University, Xi＇an 710072, China）
43-1239/TG
dual-alloy; hot deformation; processing map; apparent activation energy; microstructure
ISSN:1003-6326