La对定向凝固Al-4.5%Cu合金热疲劳性能的影响

Effect of La on Thermal Fatigue Property of Unidirectional Solidification of Al-4.5%Cu Alloy

采用自约束热疲劳试验机,对加入La的定向凝固Al-4.5%Cu合金进行热疲劳性能试验。结果表明,加入适量La对定向凝固Al-4.5%Cu合金的热疲劳性能有不同程度提高,其中,加入0.3%La的热疲劳试样疲劳性能较佳,达到热疲劳裂纹萌生所需的热疲劳循环次数最多;通过热疲劳循环次数与主裂纹长度的动态关系图,发现热疲劳裂纹的扩展有别于一般由机械交变载荷造成的常温疲劳,呈现先快后慢,阶段性扩展。

The thermal fatigue property of unidirectional solidified AI-4.5%Cu alloys with La was tested on self-restrict thermal fatigue experimental machine. The results show that the suitable addition of La has obviously improved the thermal fatigue property of unidirectional solidification of AI-4.5%Cu alloys. The thermal fatigue property of alloys with 0.3%La is quite fine, and the initiation of crack reaches the highest thermal fatigue cycle index. Dynamic relationship diagram of thermal fatigue cycle index and main crack length show that the propagation of thermal fatigue crack is fast at first and then slow, which is different from the fatigue caused by mechanical alternate loads at normal temperature.