Phase transformation and thermal expansion of Cu/ZrW2O8 metal matrix composites
Phase transformation and thermal expansion of Cu/ZrW2O8 metal matrix composites
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DOI：
10.1557/jmr.1999.0104
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发表时间：
1999-03-01
影响因子：
2.7
通讯作者：
Dunand, DC
中科院分区：
文献类型：
--
作者：
Holzer, H;Dunand, DC
采用粉末冶金法制备了完全致密、未反应的复合材料，该复合材料由含有50-60%体积分数的负热膨胀的ZrW2O8颗粒的铜基材料组成。在25至300摄氏度的循环中，复合材料的热膨胀系数随温度变化很快，明显大于理论预测的热膨胀系数。加热时的异常大膨胀和冷却时的收缩归因于ZrW2O8在其高压伽马相和其低压α或β相之间的同素各向同性转变所引起的体积变化。根据量热和衍射实验以及简单的应力估算，这种同素各向异性转变是由于基体和增强体之间的热膨胀失配而引起的颗粒内的流体静力热应力的结果。
Powder metallurgy was used to fabricate fully dense, unreacted composites consisting of a copper matrix containing 50-60 vol% ZrW2O8 particles with negative thermal expansion. Upon cycling between 25 and 300 degrees C, the composites showed coefficients of thermal expansion varying rapidly with temperature and significantly larger than predicted from theory. The anomalously large expansion on heating and contraction on cooling are attributed to the volume change associated with the allotropic transformation of ZrW2O8 between its high-pressure gamma-phase and its low-pressure alpha- or beta-phases. Based on calorimetry and diffraction experiments and on simple stress estimations, this allotropic transformation is shown to result from the hydrostatic thermal stresses in the particles due to the thermal expansion mismatch between matrix and reinforcement.