航空铝合金系列材料裂纹扩展性能的温度效应

高低温裂纹扩展性能是航空金属结构损伤容限设计的前提,为此,试验测定了3种系列的6种航空铝合金材料(2024-T351、2397-T8、6061-T651、7050-T7451、7050-T7452和7475-T761)在5种温度环境(-70、-54、25、125和150℃)下的裂纹扩展性能,观测了试验现象,并进行了性能对比分析和疲劳断口扫描电子显微镜(SEM)分析,研究了温度对航空铝合金材料裂纹扩展性能的影响机制,获得了具有工程参考价值的结果与结论:与25℃相比,低温下裂纹扩展阻力系数的对数值降低7%~15%,而高温下却增大5%~23%;低温下裂纹扩展指数增大7%~21%,而高温下却减少5%~34%;氢脆效应和高温氧化作用是导致裂纹扩展速率随温度升高而加快的主要原因。

Temperature effect on crack propagation properties of aluminum alloys in aircraft

Fatigue properties on crack propagation rate at low and elevated temperatures are the precondition of damage tolerance design for aviation metallic structures.Therefore,in order to determine fatigue properties on crack propagation rate,fatigue tests were performed on six categories of aluminum alloys (i.e.2024-T351,2397-T8,6061-T651,7050-T7451,7050-T7452,7475-T761) at five kinds of temperatures (-70 ℃,-54 ℃,25 ℃,125 ℃,150 ℃) under constant amplitude loading,and fatigue crack propagation properties were determined and the comparisons between fatigue properties on crack propagation rate at different temperatures were carried out.The mechanisms of temperature effect on crack propagation rate were deduced from fractographic studies by using scanning election microscope (SEM).The results show that,compared with the situation at 25 ℃,logarithmic crack propagation resistance coefficient decreases by 7％ to 15％ at low temperature,but increases by 5％ to 23％ at elevated temperature;crack propagation exponent increases by 7％ to 21％ at low temperature,but decreases by 5％ to 34％ at elevated temperature,compared with the situation at 25 ℃;hydrogen embrittlement and oxidation effects are likely to be the main reasons for more rapid crack propagation with the increasing temperature.