Zr基块状非晶的氢损伤与氢致滞后断裂

HYDROGEN DAMAGE AND DELAYED FRACTURE IN Zr BASE BULK METALLIC GLASS

研究了Zr41.2Ti13.8Ni10Cu12.5Be22.5块状非晶在充氢过程中氢致滞后断裂规律以及氢鼓泡的形核、长大及破裂过程.结果表明,当充氢电流i<20 mA/cm2时,不出现氢损伤(鼓泡及微裂纹),但在恒载荷条件下能发生氢致滞后断裂,其归一化门槛应力强度因子为KIH/KIC=0.63.当i>20 mA/cm2后,无载荷下充氢会产生氢损伤,恒载荷下发生滞后断裂时KIH/KIC从0.63降为0.26.氢鼓泡(直径约为30 nm)形核时的内压pi≈3.6 GPa.随氢的进入,鼓泡不断长大;内压增大至pC≈3.9 GPa时,鼓泡就会解理扩展变成裂纹;但扩展20-30 μm后,内压下降从而止裂.当一定量原子氢进入氢鼓泡后,它又能解理扩展,从而在鼓泡边缘局部解理断口上可以观察到止裂线.

Initiation, growth and breakage of hydrogen blistering and hydrogen-induced delayed fracture under constant load in bulk metallic glass Zr41.2Ti13.8Ni10CU12.5Be22.5 have been investigated. The results show that when charging current density i < 20 mA/cm(2), there are no hydrogen blisterings and microcracks on the surface of the specimens and the normalized threshold stress intensity factor is K-IH/K-IC=0.63. where K-IC = 62.2 MPa(.)m(1/2). When i greater than or equal to 20 mA/cm(2) hydrogen blisterings and microcracks appear in the specimen under no loading, while KIH/KIC decreases from 0.63 to 0.26. The critical pressure necessary for a stable blistering formation is p(i) approximate to 3.6 GPa, and that for cleavage propagation of the blistering is p(c) approximate to 3.9 GPa. The crack formed through blistering cracking will be arrested after propagating 20 to 30 mum., and the arrested crack will propagate again because of entering of hydrogen atoms. At last, the blistering with cracking will be broken and leave local cleavage fracture surface with arrested lines on the surface of the sample without loading.