Stir-casting manufactured SiCp reinforced aluminum matrix composite with ultrahigh strength and excellent corrosion resistance: Matrix, microstructure and properties

This study successfully developed a stir casting aluminum matrix composites with ultra-high strength and excellent corrosion resistance. The matrix of the composites was a high-alloyed Al-Zn-Mg-Cu alloy, with the design composition of Al-11.3Zn-3.0Mg-1.15Cu-0.013Sr-0.279Zr-0.078Ti-0.5Ce. The reinforcement of the composites was SiC particles (SiC p ) with a particle size of 10 μm and a content of 10 wt.%. The composites was prepared through stir casting, homogenization, extrusion, solid solution, and aging, and exhibiting superior properties with the density of 2.925 g/cm 3 , the elastic modulus of 92.5 GPa, the yield strength of 762.6 MPa, the tensile strength of 779.4 MPa, and the electrochemical corrosion current density in a 3.5 wt.% NaCl solution of 1.779 × 10 -6 A/cm 2 . The interface structure was Al/(Zn,Mg)Al 2 O 4 /SiC besides Al/SiC. The interface was clean, without aging precipitates. The grain boundary precipitates exhibited a discontinuous distribution. Quantitative calculations indicated that the elastic modulus of the composites conforms to the Halpin-Tsai model. The contributions to strength for solid solution, dislocations, low angle grain boundaries, high angle grain boundaries, aging precipitation, and load transfer were approximately 92.9 MPa, 157.83 MPa, 80.85 MPa, 18.05 MPa, 375.6 MPa, and 67.05 MPa, respectively. The ultra-high strength and excellent corrosion resistance were related to the design of the matrix composition, uniform dispersion of SiC p , and good interface bonding.