Effects of Sr content on the microstructure and mechanical properties of cast Al–12Si–4Cu–2Ni–0.8Mg alloys

摘要: Abstract The influence of Sr content on the microstructure and mechanical properties gravity cast Al–12Si–4Cu–2Ni–0.8Mg alloy is reported. From SEM, EDS XRD results, five kinds intermetallic phases including Al 2 Cu, 7 Cu 4 Ni, 3 CuNi, AlSiFeNiCu-Aluminide 5 Mg 8 Si 6 are detected. Metallographic image analysis techniques have been used to quantitatively examine microstructural changes at different contents. After additions, morphology eutectic silicon changing from acicular fibrous, cells formed block-like strip-like. When addition increased 0 wt.% 0.02 wt.%, secondary dendrite arm spacing (SDAS) reduced 18 μm 13 μm, there were no noticeable volume phase. results in ultimate tensile strength 196 MPa 249 MPa, yield 176 MPa 207 MPa, elongation increase 0.74% 0.95% quality index ( Q ) 246 MPa. 0.02 wt.% 0.04 wt.%, SDAS 13 μm 21 μm, phase 1.4 vol.% 0.8 vol.%. As a result, 249 MPa 226 MPa, 207 MPa 165 MPa, 246 MPa 219 MPa. A typical brittle fracture mode was observed fractograph. Plate-like particles interdendritic regions acted as an easy path for crack propagation.