| Because of good biocompatible and biodegradable, Magnesium and magnesium alloys have became the research focus in the field of biomedical materials. With the deepening of the study, many scholars have found that the corrosion rate of magnesium and magnesium alloys were too fast, which was faster than the speed of tissue repair. Degradation rate control of magnesium and magnesium alloys as biomaterials is an urgent problem needed to resolve. Plastic deformation can improve the mechanical properties of materials, so, it has became a research hotspot in recent years. With the deepening of the study, some scholars found that plastic deformation could improve the corrosion resistance of materials, and there was a close relationship between deformation uniformity and corrosion resistance. This means that we can control the corrosion resistance of materials by controlling the deformation uniformity while using plastic deformation to improve the material mechanical performance. This paper aims to study extrusion uniformity and its influence on biological corrosion resistance of magnesium, which is of great practical significance for magnesium as biomedical materials.In this paper, high pure magnesium(purity:99.95%) was taken as our research object. With the aid of numerical simulation technology, the commercial software DEFORM was used to carry out the Finite Element Analysis of anti-extrusion process, and the extrusion samples were conducted Hank 's solution immersion test. Through testing the PH value, analyzing weight loss, testing SEM and EDS, the corrosion resistance of anti-extrusion samples in SBF was analyzed, and the relationship between corrosion resistance and deformation uniformity was confirmed. In order to get better uniformity samples, Equal Channel Angle Pressing(ECAP)was introduced to study the influence of pass numbers, extrusion route,extrusion temperature,extrusion speed and friction coefficient on deformation uniformity. and the deformation uniformity coefficient of the anti-extrusion and equal channel angular pressing was compared.(1) The displacement-stroke curve of the Finite Element Analysis and actual extrusion was analyzed,which indicated that the Finite Element Analysis model established in this paper was effective. The results of the Finite Element highly coincided with the actual experimental.(2) The anti-extrusion process was analyzed through the Finite Element Analysis, and the conclusion was drawed: in the process of anti-extrusion, the smaller the extrusion ratio, the better the uniformity of deformation; Under the condition of the same extrusion ratio, at 300?,we could get the best deformation uniformity.(3) Through SBF Hank's solution immersion test, it was concluded that the corrosion rate of five kinds of solutions was ER50(300 ?) > ER30(350 ?) > ER30(250 ?) > ER30(300 ?) > ER10(300 ?). Therefore, the smaller the extrusion ratio,the better corrosion resistance, under the condition of the same extrusion ratio, at 300 ?,the corrosion resistance of pure magnesium was relatively good.(4) The deformation uniformity has direct relationship with corrosion resistance: the better the deformation uniformity, the better the corrosion resistance.(5) Through the Finite Element Analysis of Equal Channel Angular Pressing, the results showed that deformation uniformity of extrusion was increased when the extrusion passes was increased before 4 times, but there was a little influence on the deformation uniformity after 4 times.(6) Through orthogonal tests for ECAP based on Finite Element Analysis, the results showed that ECAP extrusion route has the biggest impact on the deformation uniformity,and BC route was the best way as for four kinds of extrusion routes; Friction coefficient was smaller, the better the uniformity; We could get relatively good deformation uniformity when temperature was 300 ?.(7) The anti-extrusion deformation uniformity and Equal Channel Angular Pressing deformation uniformity coefficient was compared, we could see that Equal Channel Angular Pressing was better than the anti-extrusion. |
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