PZT-5铁电陶瓷恒载荷压痕裂纹在空气和水中的扩展过程

PROPAGATION PROCESS OF INDENTATION CRACKS IN AIR AND WATER UNDER A SUSTAINED LOAD FOR PZT-5 FERROELECTRIC CERAMICS

用Vickers硬度计作为加载装置,研究了极化锆钛酸铅(PZT-5)铁电陶瓷压痕裂纹恒载荷下在室温空气和水中的扩展规律.结果表明,恒载荷下,压痕裂纹在空气和水中不断扩展, 120 h后趋于稳定,从而就可获得裂纹扩展速率和裂纹止裂的门槛应力强度因子KISCC,它们均显示各向异性.研究表明,裂纹扩展速率和KISCC的各向异性与铁电陶瓷断裂韧性的各向异性有关,即裂纹扩展速率随KIC的增加而降低,而KISCC随KIC的增加而升高.平行极化方向裂纹的断裂韧性比垂直极化方向高,即KCIC<KaIC,因此,在空气或水中的应力腐蚀更敏感,即KISCCc <KISCCa,dc/dt>dn/dt;与在空气中相比,在水中应力腐蚀更敏感,即裂纹扩展速率更高、门槛值更低.

The propagation processes of indentation cracks in air and water under a sustained load for a PZT-5 ferroelectric ceramics have been investigated. The results show that the indentation cracks could propagate in air and water and arrest after about 120 h. As a result, the crack propagation rates and threshold stress intensity factors for crack arrest in air and water were obtained, and revealed anisotropy. The anisotropy of susceptibility to stress corrosion cracking is relative to the anisotropy of the fracture toughness. The fracture toughness of the crack perpendicular to the poling direction is smaller than that parallel to the poling direction, i.e., K-IC(c) < K-IC(a), and thus the susceptibility to stress corrosion cracking in air and water for the crack perpendicular to the poling direction is larger than that parallel to the poling direction, i.e., K-ISCC(c) < K-ISCC(a) and dc/dt > da/dt. Stress corrosion cracking in water is more susceptible, i.e., da/dt is larger and K-ISCC is smaller, than that in air.