Effect of ultrasonic and mechanical vibration treatments on evolution of Mn-rich phases and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys
Bo Lin, Xiang-xiang HE, Songchao Xia, Huaqiang Xiao, Yuliang Zhao, Khashayar Khanlari
Abstract
Effects of ultrasonic vibration (UV) and mechanical vibration (MV) on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated. The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures. In addition, UV treatment can significantly passivate the primary Mn-rich Al 15 Mn 3 Si 2 intermetallics. The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed. Compared with the gravity die-cast alloys, the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures. These results can be attributed to the refinement of the α (Al) grains and the secondary intermetallics, the increased proportion of refined heat-resistant precipitates, and the formation of nano-sized Si particles. The ultimate tensile strength of the UV treated alloys at 350 °C exceeds that of commercial piston alloys. This indicates the high application potential of the developed piston alloys in density diesel engines.