MgO-ZrO_(2)耐火骨料的制备及其抗热震行为

Preparation and Thermal Shock Behavior of MgO-ZrO_(2) Refractory Aggregates

在轻烧MgO粉中添加5%(质量分数)、10%、15%及20%m-ZrO_(2)粉,于1600℃条件下制备了MgO-ZrO_(2)耐火骨料,研究了ZrO_(2)含量对材料烧结行为、显微结构、力学性能、热学性能及抗热震性能的影响。结果表明:ZrO_(2)主要弥散分布于方镁石晶界处,抑制了方镁石晶粒异常长大,促进了气孔排出,部分m-ZrO_(2)与MgO发生固溶形成c-ZrO_(2),活化了方镁石晶格,促进了试样烧结及致密化,但ZrO_(2)超过10%会导致Mg O晶界处形成较多微裂纹,使得试样致密度略微降低。添加ZrO_(2)后,方镁石晶粒间结合减弱,试样强度略降低,裂纹扩展方式以沿晶断裂为主,发生偏转及分叉效应,使得试样断裂韧性K_(IC)显著提高。当ZrO_(2)添加量为20%时,试样中Mg O晶粒最小,裂纹扩展路径最长,表现出最佳K_(IC)。此外,添加ZrO_(2)虽然会导致试样导热率λ呈下降趋势,但试样K_(IC)明显提高,热膨胀系数α不断降低,试样抗热震性能得到提高。ZrO_(2)添加量5%试样的残余抗折强度及残余抗折强度保持率均最高,表现出最佳的抗热震性能。

In order to improve the thermal shock resistance of magnesia aggregates,MgO-ZrO_(2) refractory aggregates were prepared at 1 600℃via adding 5%(in mass fraction),10%,15%and 20%of m-ZrO_(2) powder into light burned magnesia powder.The effect of ZrO_(2) content on the sintering behavior,microstructure,mechanical properties,thermal properties and thermal shock resistance was investigated.The results show that ZrO_(2) is mainly distributed at the grain boundary of periclase,which can inhibit the abnormal growth of periclase grains and promote the discharge of pores.Some m-ZrO_(2) interacts with MgO to form c-ZrO_(2) solid solution,thus activating the periclase lattice and promoting the sintering and densification of specimens.However,more than 10%ZrO_(2) addition can lead to the more micron-cracks formation at the grain boundary of MgO,which can slightly reduce the density of the specimens.For a specimen with ZrO_(2),the strength of the specimen reduces slightly and the main crack propagation mode becomes intergranular fracture due to the weakened intergranular bonding of periclase.Also,crack deflection and branching effect occurs after adding ZrO_(2),leading to an improvement of the fracture toughness K_(IC),and the specimen with 20%ZrO_(2) addition has the optimum K_(IC) due to its smallest MgO grain and the longest crack propagation path.In addition,although the addition of ZrO_(2) results in a decreasing thermal conductivityλ,the K_(IC) of the specimen increases and the coefficient of thermal expansionαdecreases,the thermal shock resistance of the specimen improves.The specimen with 5%ZrO_(2) addition has an optimum thermal shock resistance due to its maximum residual flexural strength and residual flexural strength retention rate.