氢对Ti-2Al-2.5Zr钛合金疲劳裂纹扩展速率的影响

Effects of Hydrogen on Fatigue Crack Propagation Rate of Ti-2Al-2.5Zr Titanium Alloy

对3种含氢量的Ti-2Al-2.5Zr钛合金的室温疲劳裂纹扩展速率进行了实验测定,并对断裂以后的试样进行了断口观察。实验结果表明:含氢Ti-2Al-2.5Zr的稳态裂纹扩展符合Paris幂律关系;氢对裂纹稳态扩展阶段的疲劳裂纹扩展速率(da/dN)基本没有影响, 但对失稳快速扩展行为影响较大;氢含量越高,开始发生疲劳裂纹失稳快速扩展的应力强度因子范围越低;高含氢量的试样在应力强度因子范围(ΔK)高时发生氢化物的择向开裂,降低了材料的断裂韧性,导致裂纹失稳快速扩展所需的ΔK比低氢含量所需的ΔK小。

The fatigue crack propagation rates of Ti-2Al-2.5Zr titanium alloy with three different hydrogen contents were measured at room temperature and the fracture surfaces were observed. Experiment reveals that behavior of the stable crack propagation conforms to the Paris Law, and hydrogen has little effects on da/dN in the stable crack propagation stage, but has marked effects on da/dN in the rapid fracture stage. Increasing hydrogen leads to decrease the stress intensity factor range delta ΔK at which the rapid rupture starts. Direction-preferable cracking of hydrides occurs in material with the highest hydrogen concentration at higher delta ΔK, so as to decrease the fracture toughness, which results in the smaller delta ΔK needed for the rapid rupture than the lower hydrogen materials.