Microstructure, mechanical performance and oxidation mechanism of boride in situ composites
Microstructure, mechanical performance and oxidation mechanism of boride in situ composites
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DOI：
10.1016/s0266-3538(00)00187-1
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发表时间：
2001-05
影响因子：
9.1
通讯作者：
Chang-Ming Chen;L. T. Zhang;W. C. Zhou;Z. Hao;Y. Jiang;S. Yang
中科院分区：
文献类型：
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作者：
Chang-Ming Chen;L. T. Zhang;W. C. Zhou;Z. Hao;Y. Jiang;S. Yang
采用悬浮区熔法制备的LaB 6-ZrB 2共晶原位复合材料具有优异的力学性能，是制造涡轮机叶片的理想材料。对悬浮区熔法制备的复合材料的研究表明，ZrB_2纤维的平均直径为0.2-1.2 μm，纤维长度可达100 μm。LaB 6是共晶生长时首先形核的相，ZrB 2为非小面生长。在平面生长凝固的铸锭中，各相的取向关系为：[001] LaB 6//[00.1] ZrB 2，界面平面为（110）LaB 6//（12.0）ZrB 2。裂纹扩展沿着和垂直于纤维的方向分别表现出8.7和17.8 MPa m1/2的韧性。研究了LaB_6-ZrB_2共晶自生复合材料在912-1223°C、1.5× 10_4 -7.2× 10_4Pa压力范围内的氧化行为。在912-1094°C的温度范围内，重量的变化率可表示为kp=9.71×10−3exp（−31000/RT）mg 2cm − 4 min − 1。当温度高于1094°C时，氧化动力学迅速，氧化皮主要成分为La 2 O3·B2 O3和La 2 O3·3B 2 O3，氧化皮外层缺乏ZrO 2。
In situ composite of LaB6–ZrB2eutectic prepared by floating zone melting is an interesting candidate for the manufacture of turbine blades because of its excellent mechanical properties. Studies of a composite prepared by floating zone melting showed that the average diameter of the ZrB2fibers was ∼0.2–1.2 μm, with fiber lengths up to 100 μm. LaB6was the first phase to nucleate when eutectic growth occurred, and ZrB2shows non-faceted growth. In an ingot solidified with planar growth, the orientation relationship of the phases was: growth direction [001]LaB6//[00.1]ZrB2, interfacial plane (1 10)LaB6//(12 .0)ZrB2. Crack extensions along and perpendicular to the direction of fibers exhibit toughness of 8.7 and 17.8 MPa m1/2, respectively. The oxidation behavior of LaB6–ZrB2eutectic in situ composites was studied in the temperature range of 912–1223°C and in the pressure range 1.5×104–7.2×104Pa. The rate of weight change is described by kp=9.71×10−3exp(−31000/RT) mg2cm−4min−1in the range 912–1094°C. Above 1094°C, rapid oxidation kinetics were observed, La2O3·B2O3and La2O3·3B2O3being the primary scale constituent with ZrO2deficiency in the outer scale.