Al alloy/Ti2AlC复合材料的压缩性能和裂纹扩展
Compressive performance and crack propagation in Al alloy/Ti2AlC composites
摘要：
采用电流激活压力辅助熔渗工艺制备了多孔Ti 2AlC基体与Al 6061合金的复合材料。用铝合金填充不同尺寸的孔隙，制备了粗、中、细三种细观结构。材料进行单轴压缩载荷高达668 MPa的应力，导致通过在两个阶段中的裂纹扩展的试样的故障。通过X射线显微镜和电子显微镜对制造和失效后的试样进行分析。准静态力学测试结果表明，细结构复合材料的压缩强度最高。而粗糙结构的试样表现出相对于此的80%的压缩强度。重建的微尺度X射线断层扫描数据揭示了不同的裂纹扩展机制。大的平面剪切裂纹在整个精细结构的材料中传播，而较粗的试样表现出网络的分支裂纹传播优先沿Al合金-Ti 2AlC相界面和通过收缩孔在Al合金相。结果表明，控制孔隙率、补偿Al合金收缩和改善Al合金-Ti 2AlC相界面是设计高性能金属/Ti 2AlC相复合材料的关键。
英文摘要：
Composite materials comprising a porous Ti2AlC matrix and Al 6061 alloy were fabricated by a current-activated pressure assisted melt infiltration process. Coarse, medium and fine meso-structures were prepared with Al alloy filled pores of differing sizes. Materials were subjected to uniaxial compressive loading up to stresses of 668 MPa, leading to the failure of specimens through crack propagation in both phases. As-fabricated and post-failure specimens were analysed by X-ray microscopy and electron microscopy. Quasi-static mechanical testing results revealed that compressive strength was the highest in the fine structured composite materials. While the coarse structured specimens exhibited a compressive strength of 80% relative to this. Reconstructed micro-scale X-ray tomography data revealed different crack propagation mechanisms. Large planar shear cracks propagated throughout the fine structured materials while the coarser specimens exhibited networks of branching cracks propagating preferentially along Al alloy-Ti2AlC phase interfaces and through shrinkage pores in the Al alloy phase. Results suggest that control of porosity, compensation for Al alloy shrinkage and enhancement of the Al alloy-Ti2AlC phase interfaces are key considerations in the design of high performance metal/Ti2AlC phase composites.
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