机械合金化合成NiAl/HfB_2复合材料的组织与力学性能

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF MECHANICALLY SYNTHESED NiAl/HfB_2 COMPOSITE

球磨Ｎｉ，Ａｌ；Ｈｆ和Ｂ元素粉末反应合成ＮｉＡｌ／ＨｆＢ２复合材料，形成机制归结为机械碰撞诱发的自蔓延反应．采用 热压和热等静压工艺将纳米双相复合粉末压制成较密实的块体材料，进而研究其微观组织与力学性能．结果表明“反应球磨＋热 压”制备的ＮｉＡｌ／ＨｆＢ２复合材料基体晶粒细小，原位生成的弥散相颗粒主要分布于基体晶界，其强化效果显著而对塑性的削弱 作用较小；不同温度下的压缩屈服强度均远高于铸态ＮｉＡｌ，且压缩变形量均超过１０％；高温下材料的屈服强度依赖于应变速率， 用线性回归方法计算出的应力指数ｎ和变形激活能Ｑ高于单相ＮｉＡｌ，与含弥散相比例较高的ＸＤ ＮｉＡｌ－２０％ＴｉＢ２（体积分数） 复合材料相当．

Mixed elematal powders of Ni, Al, Hf and B were ballmilled to reaction synthesize NiAl/HfB2 composite. The formation mechanism can be attributed to self propogating reaction induced by mechanical collision. The microstructure and compressive properties of densified bulk prepared by hot pressing and isostatically pressing have been investigated. The results show that the fine HfB2 reinforcing particles formed by in situ mode distributed mainly in matrix. The yield strength of NiAl/HfB2 composite is much stronger than that of NiAl, furthermore, it also possess good compressive ductility at low temperature. The yield strength of NiAl/HfB2 composite at high temperature is dependent on strain rate. The stress exponent n as well as activity energy Q calculated by standard power law are much higher than NiAl and similar to NiAl composite with a higher volume fraction of TiB2 dispersoids.