Microstructure of Al4Sr Phase in Al-Sr Master Alloy and its Effect on Modification Properties

AbstractAl-Sr master alloys were prepared by “Direct reaction method” and “Direct reaction - hot extrusion method”, respectively, in the present study, and the microstructure including the morphology, size, structure, hardness, and elastic modulus of Al4Sr phase, as well as the fracture morphology of the Al-Sr master alloys have been analyzed and examined by means of the Metallurgical Microscope, X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Nanoindentation device. And a new growth model of Al4Sr was proposed. The results showed that the Al4Sr intermetallic phase with small size of 10∼30μm in length and 5∼20μm in width were evenly distributed in the aluminium matrix in the Al-Sr master alloys prepared by “Direct reaction - hot extrusion method”. These microstructure characteristics guaranteed their excellent modification performance, good thermoforming properties and good machinability. By controlling the processing parameters of the Al-Sr master alloys, the morphology of Al4Sr can be controlled, and then the Al-Sr master alloys with better modification performance and higher Sr content can be obtained