碳纤维增强Al-4.5Cu复合材料的凝固组织、偏析及性能的研究

铸造金属基复合材料的凝固决定着材料的机械性能.本文中研究了凝固冷却速率对CF/Al-4.5Cu复合材料的显微组织、偏析及机械性能的影响.实验结果表明,挤压铸造CF/Al-4.5Cu复合材料凝固过程中,α-Al相首先在纤维间隙中开始形核,并逐渐向纤维表面生长,而共晶θ-Al₂Cu相依附CF表面形核并长大.随着凝固冷却速率的降低,θ相的形态从块状转变为颗粒状,析出量逐渐减少,Cu元素显微偏析逐渐降低,复合材料的抗弯强度逐渐提高.另外,CF/Al-4.5Cu复合材料由于其强的界面结合力,其断裂特征为脆性断裂,断口形貌表现为平切型.

INVESTIGATION ON THE SOLIDIFICATION MICROSTRUCTURE, MICROSEGREGATION AND MECHANICAL PROPERTIES OF CF/AL 4.5Cu METAL MATRIX COMPOSITES

The solidification processing of metal matrix composites has a strong influence on their mechanical properties. In the present work, the effects of solidification cooling rate on the solidification microstructure, microsegregation and mechanical properties of CF/Al-4.5Cu metal matrix composites were investigated experimentally. The results showed that during the solidification processing of squeeze casting CF/Al-4.5Cu composites, α-Al phase nucleated first in the interstice regions of CF, but eutectic θ-Al2Cu phase nucleated and grew on the surface of CF. As the solidification cooling rate decreased, crystallized quantity of θ-Al2Cu phase also decreased; its shape was changed from large block-like to particle-like; meantime, the microsegregation of Cuelement also decreased, but the bent strength of the composites increased. Besides, because the fiber-metal interface was strongly bonded in the CF/Al-4.5Cu composites, the fracture surface of the composites showed the characters of brittle fracture, and no fiber pull-out was observed in any of these composites.