【摘要】 由于脆性本质所决定,大部分陶瓷材料对热应力断裂很敏感。根据断裂力学理论,热应力断裂包括裂纹成核以及裂纹连续扩展过程。而且,裂纹扩展阶段似更危险。指出,断裂面积动态扩张过程的动力与抗热震参数R成反比。R≌(K_1C/σ_f)²,这里K_1C是临界应力强度因子,σ_f是抗张强度。 为了探讨上述规律,以显微结构不同的三种Al₂O₃基陶瓷为对象,研究其断裂韧性参数(亦即临界应力强度因子K_1C),抗热震参数与很宽淬火温差范围内的热震强度损失率间的关系。结果表明,由于晶界结合力较弱,以沿晶方式断裂的T-Al₂O₃较P-Al₂O₃和Ⅱ-95-Al₂O₃具有低得多的强度。然而,其K_1C值略高于Ⅱ-95-Al₂O₃的K_1C值。这是由于晶界起了分散能量的作用。结果得到的高R值与其淬火后较小的强度损失率一致。以穿晶断裂方式为主的Ⅱ-95-Al₂O₃强度值最高,K_1C值较低,预示了低的R值和必然的高热震强度损失。P-Al₂O₃具有的高强度和较高的K_1C值使其拥有中等的抗热震参数值,相应于一定的热震强度损失。 很明显,R值可作为衡量脆性陶瓷强度相对变化的判据,而后者是材料热震严重程度的函数。建议以K_1C和抗折强度作为实验室的常规测试,用于陶瓷材料的生产控制和发展。更多还原

【Abstract】 Most of the ceramic materials, because of their inherent brittleness, are susceptible tothermal stress fracture. According to fracture mechanics theory, thermal stress fracture includ-es processes of flacture intiation as well as of continued crack propagation.of the two,crack propagation is more detrimental.It has been proposed that crack propagation occurs kinetically with total area of crack propagation inversly proportional to thermal shock re-sistance parameter, e. g.R≌(K_1c/σ_f)², where K_1c is the critical stress intensity factor,σ_f, isthe tensile strength. In order to investigate this relationship,the critical stress intensity factor and the ther-mal shock resistance parameter of three types of alumina ceramics with different micro-structures were compared with their strength losses over a wide range of quenching tempe-rature difference （200℃<ΔT<1200℃） .Because of their structural weakening at grain boun-daries, type T-Al₂O₃ samples, which fracture almost in a completely intercrystallilae man-ner, have strength values considerably lower than those of type P-Al₂O₃ and type Ⅱ-95-Al₂O₃ samples. Nevertherless, their K_1c values are somewhat higher than those of type Ⅱ-95-Al₂O₃.This can be explained by energy dissipation at such grain boundaries. Their result-ing high R values coincide with the small degradation of strength in quenching. The highstrength value and low K_1c value of type Ⅱ-95-Al₂O₃ samples, which fracture mainlytranscrystallinely, indicate a low value of R and a consequent high strength loss in quench-ing. The relatively high K_1c value, together with the high strength value of type P-Al₂O₃samples produce an intermediate R value, corresponding to certain degradation of strengthin quenching. Apparently, for brittle ceramics the value of R could be the criterion for estimation ofthe relative change in strength which is a function of thermal shock.It is recommendedthat the critical stress intensity factor K_1c, as well as the strength value σ_f, be determinedas a routine laboratory practice in the production and development of n?aterials.更多还原