(铜仁学院 物理与电子科学系，铜仁 554300)
摘 要: 研究不同加钛方式和钛含量对铸造A356铝合金常温低周疲劳行为的影响，分析合金疲劳断口的形貌特征。结果表明：4种A356合金均表现出明显的循环硬化行为，但Ti含量(质量分数)为0.14%的合金比Ti含量为0.10%的合金具有更高的循环硬化率。在低应变时，加钛方式对合金的循环硬化影响相近；而在高应变时，电解加钛A356合金表现为类似“饱和”的准稳定形变行为，熔配加钛合金则表现为持续的循环硬化特征。加钛方式对A356合金低周疲劳寿命的影响不明显，其疲劳寿命仅受合金中Ti含量的影响；Ti含量为0.10%的A356合金较Ti含量为0.14%的合金具有更优异的低周疲劳寿命，这主要是由于前者具有较低的屈服强度。
关键字: A356合金；低周疲劳；循环硬化；疲劳寿命
（Department of Physics and Electronics Science, Tongren University, Tongren 554300, China）
Abstract:Effects of the method of Ti-alloying and Ti contents on the low cycle fatigue (LCF) behavior of cast A356 alloys at room temperature were investigated, and the morphologies of fracture surfaces were analysed. The results show that four kinds of A356 alloys exhibit the evident cyclic hardening behavior, and the A356 alloys with 0.14%Ti(mass fraction) exhibit higher cyclic hardening rate than the alloys with 0.1%Ti. The cyclic hardening behavior influenced by method of Ti-alloying has similar trend when tested at low strain amplitude; while the A356 alloys by electrolysis (EA356) tested at high strain amplitude, reveal the quasi-stable deformation resembled “saturation” state, and for the A356 alloys by melting Al-10%Ti master alloys (MA356), the cyclic hardening continuously proceeds. There is no obvious difference between the LCF lives of A356 alloys fabricated by two methods of Ti-alloying, and the LCF life is only influenced by Ti contents in the alloys. The A356 alloy with 0.10 %Ti has a lower yield strength, which exhibits a longer LCF life than the alloys with 0.14%Ti.
Key words: A356 alloys; low cycle fatigue; cyclic hardening; fatigue life
