超声表面滚压加工对Zr705合金预腐蚀疲劳行为的影响

Effect of Ultrasonic Surface Rolling Process on Pre-corrosion Fatigue Behavior of Zr705 Alloy

本工作主要对原始态和超声表面滚压(USRP)态Zr705合金分别在1 mol/L LiOH溶液、3.5%NaCl溶液、5%HCl溶液中预腐蚀30d后的疲劳性能进行了研究。结果表明:原始态Zr705合金在3.5%NaCl溶液中腐蚀程度最严重,在5%HCl溶液中次之,在1 mol/L LiOH溶液中腐蚀程度最轻。这与Zr705合金在不同介质中的腐蚀机理不同有关。USRP-Zr705合金由于表层梯度结构中存在高密度的位错缺陷,较原始态Zr705合金更容易被腐蚀。经浸泡腐蚀处理,原始态Zr705合金疲劳寿命明显下降,这主要是由于试样表面在浸泡腐蚀过程中产生腐蚀损伤导致的。经浸泡腐蚀处理,USRP-Zr705试样在1mol/L LiOH溶液中的疲劳寿命较原始态Zr705合金有所提高,而在3.5%NaCl溶液、5%HCl溶液中疲劳寿命较原始态Zr705合金有所下降。腐蚀环境和表面梯度结构对锆合金疲劳性能的影响存在竞争关系:当腐蚀介质腐蚀性较弱时,表面梯度结构是影响合金疲劳性能的主要因素。当腐蚀介质腐蚀性较强时,在高应力作用下循环加载,表面梯度结构仍是影响合金疲劳性能的主要因素;在低应力作用下循环加载,腐蚀环境是影响合金疲劳性能的主要因素。

The fatigue properties of Zr705 alloy in original state and ultrasonic surface rolling(USRP)state after pre-corrosion in 1 mol/L LiOH solution,3.5%NaCl solution and 5%HCl solution for 30 d were studied.The results show that the corrosion degree of the original Zr705 alloy is the most serious in 3.5%NaCl solution,followed by in 5%HCl solution and the least in 1 mol/L LiOH solution.This is related to the different corrosion mechanisms of Zr705 alloy in different media.USRP-Zr705 alloy is more susceptible to corrosion than the original Zr705 alloy because of the high density dislocation defects in the surface gradient structure.After immersion corrosion treatment,the fatigue life of the original Zr705 alloy decreases obviously,which is mainly caused by corrosion damage on the surface of the sample during immersion corrosion.After immersion corrosion treatment,the fatigue life of USRP-Zr705 sample in 1 mol/L LiOH solution is higher than that of the original Zr705 alloy,but it is lower in 3.5%NaCl solution and 5%HCl solution.There is a competitive relationship between the corrosion environment and the surface gradient structure on the fatigue properties of zirconium alloys.When the corrosion medium is weak,the surface gradient structure is the main factor affecting the fatigue properties of zirconium alloys.When the corrosive medium is strong,the surface gradient structure is still the main factor affecting the fatigue properties under high stress cyclic loading.Under low stress cyclic loading,corrosion environment is the main factor affecting the fatigue properties.