The improved strength and ductility of ZrCp/2024Al composites with a quasi-network microstructure fabricated by spark plasma sintering and T6 heat treatment

Abstract

In this study, the 2024Al alloy improved by the various fraction of ZrC particles (ZrCp/2024Al composites) were constructed and processed through the spark plasma sintering (SPS) combined with T6 heat treatment in order to improve the strength and toughness simultaneously. The microstructure observations revealed that the interfacial bond between the ZrC and aluminum matrix was satisfactory and the quasi-network distribution of ZrC particles was demonstrated. The precipitates of Al2Cu and Al2CuMg, dissolved out from the 2024Al and ZrCp/2024Al composite during ageing process, exhibited little different in size and shape. With the introduction of ZrC particles, the ageing behavior was expedited and the time to achieve the aged hardness was prominently shortened from 12 h to 6 h as 5.0 wt% ZrC particles were introduced. The accelerated aging process benefited from dislocations, caused by the mismatch of thermal expansion coefficients between the ZrC and matrix. The ultimate hardness, yield strength, tensile strength and strain were all enhanced with the addition of ZrC particles. When 4.0 wt% ZrC particles were applied to the composites, the highest yield strength, tensile strength with superior ductility (332 MPa, 495 MPa and 12.0%) was obtained, which were 48.2%, 34.5% and 23.7% higher than that of pure 2024Al respectively. The improved tensile strength and strain are contributed to the particularly inhomogeneous quasi-network structure, which made the matrix deformation blocked, dislocation motion impeded and crack propagation path increased.