烧结MgAlON复合刚玉材料微裂纹的制备与表征  

Crack preparation and characterization of Al_2O_3-MgAlON composite sintered under normal pressure

作　　者：杨道媛[1] 朱凯[1] 毋娟[1] 千粉玲[1] 鲁占灵[1] 张锐[1] 

机构地区：[1]郑州大学材料科学与工程学院,郑州450001

出　　处：《耐火材料》2008年第5期349-353,共5页Refractories

基　　金：国家自然科学基金资助项目(50642008);河南省杰出青年基金;河南省自然科学基金资助项目(0511052300)

摘　　要：以刚玉（w（Al2O3）〉98%,粒度分为3-1 mm、≤1 mm、≤85μm和≤3μm四级）和粒度≤2μm的MgAlON为原料,聚乙烯醇溶液作结合剂,设计了3种含骨料的配方和4种不含骨料的配方,在液压机上于150MPa下保压5 s压制成型,于N2气氛下1 500℃保温2 h烧成,制成Φ20 mm×10 mm和3 mm×4 mm×36 mm的MgAlON复合刚玉试样,分别采用热震（1 100℃空冷10次）的方法和在维氏显微硬度计上施加不同压力（29.4、49和98 N）保压25 s的方法预制裂纹,然后在N2气氛保护下分别于1 100℃和1 550℃保温6 h进行裂纹愈合处理。研究了裂纹预制方法、试样的粒度组成以及获得维氏压痕时的载荷大小和保压时间对裂纹形状和尺寸的影响,愈合温度对压痕愈合情况及试样抗折强度的影响,并计算了维氏压痕的愈合速率。结果表明：（1）烧结MgAlON复合刚玉试样的热震裂纹形状不规则,长度不易准确测定。（2）维氏压痕近似菱形,虽没有出现由压痕顶角向4个方向发射的微细狭长裂纹,但用颗粒大小为数微米的粉料制备试样时容易控制维氏压痕的大小、形状和位置;在98 N载荷下保压25 s获得的压痕深度适中,形貌规则,能够愈合,便于下一步的愈合机理研究。（3）经1 100℃和1 550℃愈合处理后,压痕逐渐变小、变浅乃至消失,其抗折强度则逐渐恢复到原试样的水平。（4）压痕的愈合速率可以表示为：δV/δt=1/3CV^2（1＋ctgθ）δCV/δt。The Al2O3 -MgAlON specimens with dimensions of Φ20 mm ×10 mm and 3 mm ×4 mm ×36 mm were prepared using corundum grains （w（Al2O3） 〉98%, particle size： 3 -1 mm, ≤1 mm, ≤85 μm and ≤3 μm, respectively） and MgAlON （ particle size≤2 μm） as starting materials, PVA as binder, designing 3 formulations containing aggregate and 4 special formulations without aggregate, pressing under 150 MPa and keeping for 5 s, firing at 1 500 ℃ for 2 h in nitrogen under normal pressure, and the cracks were prepared on the specimens by thermal shock method （air cooling at 1 100 ℃ for 10 cycles） and by Vickers method （29.4, 49 and 98 N, keeping 2.5 s）, then holding at 1 100 ℃ and 1 550 ℃ for 6 h in nitrogen atmosphere for cracks healing, respectively. The influences of crack prefabricated method, grain composition, pressure of Vickers and pressure holding time on the shape and dimension of cracks were studied. Effects of healing temperature on healing degree and MOR of specimens were investigated and the crack healing rate was calculated. The results show that： （ 1 ） the cracks of MgAlON specimens prepared by thermal shock method under normal pressure were of irregular shape and uncertainty length; （2） the cracks pre- pared by Vickers method was approximate diamond -shape without slender cracks emitting from every vertex angle; but if composite specimens fabricated by particles of several micron, the crack size, shape and its site, especially that obtained under 98 N and 25 s, can be controlled exactly under a Vickers har- dometer, which makes the crack healing research easy to be conducted; （3） after healing treatment at 1100 ℃ or 1 500 ℃, the cracks became shallower and smaller even disappeared, the strength of the specimen was recovered finally; （4） a formulation for crack healing rate expressed by the cracked capacity was δV/δt=1/3CV^2（1＋ctgθ）δCV/δt.

关 键 词：烧结 MGALON 刚玉 裂纹预制 裂纹愈合 

分 类 号：TQ175.71[化学工程—硅酸盐工业] TQ174.611