Influential Factors For Microstructure And Property Of Mg-Si Alloys With Rare-earths Modification And Ultrasonic Treatment

There were eutectic Mg-3.2Si alloys as the research object in this paper, and different ratios of two compound rare-earths(Er and Ce, Er and Gd) have deteriorated the alloys. The alloys’ influencial laws of microstructure and properties have been studied with the compound rare-earths, as well as the metamorphic mechanism. Secondly, the alloys’ Mg2 Si phase was elaborated to obtain the best metamorphic alloys with ultrasonic processing. In order to find the change rules of the morphology and sizes and the microstructure and mechanical properties of impact mechanism with ultrasonic processing, the primary and eutectic Mg2 Si phases were studied.When Er and Ce were added in the eutectic Mg-3.2Si alloys, we can find some conclusions. Adding rare-earth Er alone, the growth of primary Mg2 Si phase was effectively inhibited in the solidification process. Added 0.6wt. % rare-earth Er, the average size of primary Mg2 Si phases were changed from 150μm to 40μm, and the shape turned from the coarse dendritic to irregular polyhedron shape. The refining effect is better. On the basis of the best burial metamorphism(0.6wt. % Er), added 1.0wt. % rare-earth Ce, we can obtain 5~10μm polyhedron or globular primary Mg2 Si phases. The refining effect is best. But if the rare-earth added too much, there was a bad phenomenon. In addition, the effect of tensile strength and elongation in eutectic Mg-3.2Si alloys’ composite metamorphic were very obvious. When compound added 0.6wt.% Er and 1.0wt.% Ce, alloys’ tensile strength and elongation were up to 127 MPa and 3.7% maximum.When Er and Gd were added in the eutectic Mg-3.2Si alloys, we can find some conclusions. On the basis of the best burial metamorphism(0.6wt.% Er), the anisotropic growth of the solidificational primary Mg2 Si phases can be effectively restrained with continuely added rare-earth Gd. When added 0.6wt.% Er and 0.6wt.% Gd, we can obtain 10~25μm polyhedron primary Mg2 Si phases. But if the rare-earth added too much, there was a bad phenomenon. In addition, the effect of tensile strength and elongation in eutectic Mg-3.2Si alloys’ composite metamorphic were very obvious. When compound added 0.6wt.%Er and 0.6wt.%Gd, alloys’ tensile strength and elongation were up to 112 MPa and 3.2% maximum.The best metamorphism(Mg-3.2Si+0.6Er+1.0Ce) alloys were been ultrasonic processed, we can find some conclusions. Ultrasonic treatment can effectively changed the shape and size of the primary Mg2 Si phases. When action power was more than 900 w, we obtained the granular primary Mg2 Si phases, and the refining effect is best. Ultrasonic treatment can effectively changed the shape and size of the eutectic Mg2 Si phases, too. When the action power was more than 1200 w, we obtained the fibrous eutectic Mg2 Si phases which were less than 10μm, and the refining effect is best. Moreover, Ultrasonic treatment had important effects on the alloys’ mechanical properties. With the increase of ultrasonic power, the tensile strength and elongation were also constantly increased. When ultrasonic power added to1200 w, the tensile strength and elongation were up to 158 MPa and 4.5%,which increased about 24.4% and 21.6%, respectively.The best metamorphism(Mg-3.2Si+0.6Er+0.6Gd) alloys were been ultrasonic processed, we can find some conclusions. Ultrasonic treatment can effectively changed the shape and size of the primary Mg2 Si phases. When action power was more than 1200 w, we obtained the granular primary Mg2 Si phases, and the refining effect is best. Ultrasonic treatment can effectively changed the shape and size of the eutectic Mg2 Si phases, too. When the action power was more than 900 w, we obtained the fibrous or short-rod eutectic Mg2 Si phases which were less than 5μm, and the refining effect is best. Moreover, Ultrasonic treatment had important effects on the alloys’ mechanical properties. With the increase of ultrasonic power, the tensile strength and elongation were also constantly increased. When ultrasonic power added to 1200 w, the tensile strength and elongation were up to 145 MPa and 4.1%,which increased about 29.5% and 28.2%, respectively.