摘要
采用原位观察疲劳试验方法研究了变形TiAl合金在650℃下的三维小裂纹扩展行为,利用传统疲劳裂纹扩展试验方法研究了该合金在650～800℃温度范围内的长裂纹扩展行为。结果显示,650℃下,变形TiAl合金的三维小裂纹在低于长裂纹扩展门槛值的区域依然能够扩展,并且扩展速率高于长裂纹;位于试样棱边的横向机械加工刻痕是合金三维小裂纹萌生的主要位置之一,小裂纹在扩展过程中发生偏折并在偏折处合并,合金的疲劳寿命对试样表面的不规则条状加工缺陷不敏感;在650～800℃温度范围内,合金的疲劳长裂纹稳态扩展速率对温度变化不敏感,裂纹扩展过程均显示为解理断裂,裂纹扩展门槛值受韧/脆转变温度影响,韧/脆转变温度以下温度的门槛值较低。
Three-dimensional small crack propagation behavior of deformed TiAl alloy at 650 oC was studied by in-situ observation fatigue testing, and the long crack propagation behavior of the alloy in the temperature range of 650~800 oC was studied by fatigue crack propagation tests. The results show that the three-dimensional small cracks can still grow even in the stress intensity factor region below the long crack propagation threshold value. Furthermore, the growth rates of small cracks are higher than those of long cracks in this region.The straight horizontal manufacturing nick at the sample edge is one of the main positions for the initiation of three-dimensional small crack in the alloy. Small cracks bend during the propagation and merge at positions where the bending occurs, and the fatigue life of the alloy is not sensitive to irregular strip manufacturing defects on the surface of the sample. The steady propagation rates of long fatigue cracks of the alloy are not sensitive to temperature changes in the temperature range of 650~800 oC. All the long crack propagation processes exhibit the cleavage fracture. Crack propagation threshold values are related to the ductile-brittle transition temperature, and the temperatures below the ductile-brittle transition temperature have lower threshold values.
作者
焦泽辉
于慧臣
董成利
鲁原
高帆
Jiao Zehui;Yu Huichen;Dong Chengli;Lu Yuan;Gao Fan(AECC Key Laboratory of Materials Testing and Evaluation,Science and Technology on Advanced High Temperature Structural Materials Laboratory,Beijing Institute of Aeronautical Materials,Beijing 100095,China;AECC Key Laboratory of Advanced Titanium Alloys,Beijing 100095,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2019年第2期538-544,共7页
Rare Metal Materials and Engineering
基金
国家自然科学基金(51401195)
航空科学基金(2013ZF21014)
关键词
TIAL合金
原位观察
小裂纹
疲劳裂纹扩展
TiAl alloy
in-situ observation
three-dimensional small crack
fatigue crack propagation
