热处理对AZ80镁合金疲劳性能的影响

Effect of Heat Treatment on Fatigue Properties of AZ80 Magnesium Alloy

通过对AZ80镁合金进行总应变幅控制下的室温低周疲劳实验,研究其在热锻、时效态(T5)、固溶时效态(T6)三种不同热处理状态下的循环应力响应、疲劳寿命和循环应力-应变行为。结果表明:在三种不同的热处理制度下,AZ80镁合金大体上都表现为循环应变硬化现象;此外,AZ80镁合金的应变疲劳寿命与塑性应变幅、弹性应变幅之间的关系分别服从Coffin-Manson和Basquin关系式。随着外加总应变幅的不断增大,其疲劳寿命减少。在0.3%的最小外加总应变幅下,AZ80热锻态的疲劳寿命最长;在0.9%的最大外加总应变幅下,AZ80-T5的疲劳寿命最长,而热锻态最短。此外,对疲劳断口形貌的观察结果表明,疲劳裂纹萌生于疲劳试样表面,并以穿晶方式扩展。

Through the experiment of low cycle fatigue experiment of AZ80 magnesium alloy under the total strain amplitude control at room temperature,cyclic stress response,fatigue life and the cyclic stress-strain behavior was studied under the heat treatment of hot forging,aging state （T5） and solid solution-aging state （T6）.The results show that AZ80 magnesium alloy is generally characterized as the cyclic strain hardening phenomenon under three heat treatments.In addition,the relationship between the fatigue life and the plastic strain amplitude or the elastic strain amplitude obeys the Coffin-Manson or the Basquin equation for AZ80 magnesium alloy respectively.With the increase of total strain amplitude,the fatigue life reduces.Under the minimum total strain amplitude of 0.3％,the fatigue life of hot forging state is the longest; under the maximum strain amplitude of 0.9％,the fatigue life of AZ80-T5 is the longest and hot forging state is the shortest.Moreover,the observation of the fatigue fracture morphology shows that the fatigue cracks initiate in the sample surface,and extend in a transgranular manner.