Ce-TZP/Al_2O_3层状复合材料的相变与韧化研究

TRANSFORMATION AND TOUGHENING OF Ce-TZP LAYERED MICRO COMPOSITES

Ｃｅ－ＴＺＰ（氧化铈稳定四方氧化锆多晶）材料由于剧烈的自催化相变易于产生低应力屈服，并在裂纹尖端形成狭长形相变区从而使相变增韧的效果得不到充分的发挥．本工作从改变Ｃｅ－ＴＺＰ材料的微观结构以改变其相变屈服和相变增韧行为的目标出发，在Ｃｅ－ＴＺＰ中引入了层、片状Ａｌ２Ｏ３制成Ｃｅ－ＴＺＰ／Ａｌ２Ｏ３复合材料．研究了Ｃｅ－ＴＺＰ直通切口梁试样在三点弯曲试验条件下的自催化相变特征和力学行为，以及Ａｌ２Ｏ３层片在抑制自催化相变和改变其相变增韧效果中所起的作用．研究表明，Ｃｅ－ＴＺＰ切口样在切口端部形成树根状自催化相变区，其分支和扩展与裂纹的产生与扩展相伴随；Ｃｅ－ＴＺＰ／Ａｌ２Ｏ３层片状复合材料中未看到相变区增宽现象，但Ａｌ２Ｏ３层片的存在抑制了自催化相变，使材料的相变塑性显著降低而强度显著提高，并使断裂韧性获得一定的改善．

CeO 2-stabilized tetragonal ZrO 2 polycrystals (Ce-TZP) suffers low yield strength owing to its strong tendency of autocatalytic phase transformation, which induces elongated transformation zone at crack_tips, thus restricts the perfect development of transformation_toughening. For the purpose of controlling transformation yielding and enhancing transformation toughening by modifying microstructure, Al 2O 3 layers and platelates were introduced in the matrix of Ce-TZP, obtaining Ce-TZP/Al 2O 3 micro_composites with different structural parameters. The autocatalytic phase_transformation characteristics and the corresponding behaviors, as well as the role of Al 2O 3 layers were investigated by three point_bending tests with single_edge notched beams. Results show that a root_shaped transformation zone is formed at the tip of the notch, and the generation and propagation of crack are accompanied by the branching and extending of this transformation zone. No considerable broadening of the transformation zone is observed in the Ce-TZP/Al 2O 3 microcomposite, but the existance of the Al 2O 3 layers and platelates does restrict the autocatalytic transformation which leads to decrease of transformation plasticity and increase of strength obviousely, and fracture toughness of the material is enhanced to some extent.