挤压变形Mg-Sn-Zn及Mg-Sn-Zn-Mn合金的组织结构与性能研究

发布时间：2018-03-03 03:16

本文选题：医用镁合金　切入点：力学性能　出处：《哈尔滨工程大学》2016年博士论文　论文类型：学位论文

【摘要】：近年来随着医用镁合金植入材料的需求增大,发展具有高的强韧性、优异的抗腐蚀性和生物相容性的新型医用镁基合金具有重要的学术意义和应用价值。本文中,首先设计制备了新型医用Mg-3Sn-1Zn合金,系统地研究了不同挤压变形工艺下Mg-3Sn-1Zn合金的的组织结构和性能。之后在Mg-3Sn-1Zn合金的基础上添加Mn元素,制备出Mg-3Sn-1Zn-0.5Mn合金,研究了其不同挤压变形工艺下的微观组织和性能,最后研究了Mg-3Sn-1Zn-0.5Mn合金的挤压变形机理。Mg-3Sn-1Zn合金和Mg-3Sn-1Zn-0.5Mn合金的铸态组织均由粗大不均匀的树枝晶组成,颗粒状的Mg2Sn相在树枝晶间分布,层片状的Mg2Sn相沿着晶界分布。固溶之后合金组织由粗大的等轴晶组成,Mg2Sn相完全融入到合金基体中,材料的综合性能提高。Mg-3Sn-1Zn合金和Mg-3Sn-1Zn-0.5Mn合金在不同挤压比(挤压比8、16和25)下,挤压温度290℃时合金具有最好的综合性能,组织形貌为细小的等轴晶,同时也有动态再结晶未完全的长条晶粒,力学性能优异,耐腐蚀性能较好,溶血率最大为7.3%。挤压温度290℃时随着挤压比逐渐增大,合金性能微有降低;Mg-3Sn-1Zn合金在挤压温度为310℃-370℃时,金相组织均为等轴晶,Mg2Sn相在合金基体上均匀析出,随着挤压比的增大,晶粒尺寸增大,力学性能和耐蚀性有所降低。Mg-3Sn-1Zn-0.5Mn合金在挤压温度为310℃-370℃时,金相组织为等轴晶,随着挤压比的增大,晶粒尺寸降低,力学性能和耐蚀性增大。不同挤压工艺下的Mg-3Sn-1Zn合金和Mg-3Sn-1Zn-0.5Mn合金的溶血率结果可知,这两种合金挤压变形后具有在血液环境应用的可行性。Mn元素的添加使M g-3 Sn-1 Zn-0.5 Mn合金的性能优于Mg-3Sn-1Zn合金的性能:力学性能方面,Mn元素加入可以细化Mg2Sn相,提高材料的力学性能。相同挤压比下抗拉强度同比增加约10-20MPa,延伸率同比增加约2-6%:耐蚀性能方面,Mn元素加入会降低杂质元素对镁合金的不利影响,当合金含有Zn元素时,添加Mn元素能明显降低材料的腐蚀速度。相同挤压比下自腐蚀电位由Mg-3Sn-1Zn合金的～-1.6V增加到Mg-3Sn-1Zn-0.5Mn合金～-1.5V,腐蚀电流速度同比减小约60%;溶血率方面,相同挤压比下Mg-3 Sn-1 Zn-0.5Mn合金的溶血率低于Mg-3 Sn-1 Zn合金的溶血率。Mg-3Sn-1Zn-0.5Mn合金的组织演变特征为:1)变形量增加,晶粒尺寸呈现不断减小的趋势。2)Mg-3Sn-1Zn-0.5Mn合金在固溶无变形时,颗粒状的Mn单质沿着晶界分布,在挤压变形后析出的Mg2Sn相均匀分布在合金基体上,Mg2Sn相的形状为盘状或杆状。3)孪晶的数量随着变形量的增加而减少。当变形量较小时,挤压变形使Mg-3Sn-1Zn-0.5Mn合金中固溶组织中的孪晶形态特征发生转变,转变后的孪晶可以发生退孪生现象,同时挤压变形会产生新的孪晶,退孪生的孪晶和新生成的孪晶数量上相差不大,总体孪晶数量变化较小;当变形量较大时,Mg-3Sn-1Zn-0.5Mn合金中发生退孪生现象的孪晶增加,同时较小的晶粒尺寸和较多的Mg2Sn相也抑制了变形引起的孪晶的生成,二者共同作用使孪晶数量急剧减少。Mg-3Sn-1Zn-0.5Mn合金变形机制以滑移和孪生为主,位错运动和增殖会使位错在变形过程中互相缠结、钉扎以及受晶界的阻碍而终止运动;孪生容易发生在不利于滑移的晶粒中促进塑性变形,挤压变形时变形生成的孪晶和退孪生同时发生。当变形量较大时(挤压比64),动态再结晶后较小的晶粒尺寸,使晶界滑动机制发挥了重要作用。固溶无变形和挤压变形时,Mg-3Sn-1Zn-0.5Mn合金中的孪晶均为{1012}1011型孪晶,固溶无变形时Mg-3Sn-1Zn-0.5Mn合金中{1012}孪晶的长大机制为经典的孪生位错机制,{1012}孪晶界小角度偏离{1012}孪晶面;挤压变形时Mg-3Sn-1Zn-0.5Mn合金中{1012}孪晶的长大机制为以扰动机制为基础,构建的扰动为主,辅助剪切的模型,孪晶界面平直,{1012}界面并不在{1012}孪晶面上,且{1012}孪晶取向差也大角度的偏离了理论上的86.3°。
[Abstract]:In recent years, with the magnesium alloy implant materials increased demand, development has a strong toughness, has important academic significance and application value of new medical magnesium alloy compatibility of corrosion resistance and excellent biological. In this paper, the first design of a new type of medical Mg-3Sn-1Zn alloy prepared by different extrusion process of Mg-3Sn-1Zn alloy the structure and properties of the system. After the addition of Mn element on the basis of Mg-3Sn-1Zn alloy, prepared Mg-3Sn-1Zn-0.5Mn alloy, research the different extrusion deformation microstructure and performance process, the study of dendritic Mg-3Sn-1Zn-0.5Mn alloy extrusion deformation mechanism of.Mg-3Sn-1Zn alloy and Mg-3Sn-1Zn-0.5Mn alloy cast by coarse uneven, granular Mg2Sn phase in the interdendritic distribution, lamellar Mg2Sn phase with grain boundary distribution. After solution alloy group The fabric from coarse equiaxed crystal composed of Mg2Sn phase completely into the alloy matrix, improve the comprehensive performance of the material of.Mg-3Sn-1Zn alloy and Mg-3Sn-1Zn-0.5Mn alloy at different extrusion ratio (extrusion ratio 8,16 and 25), extrusion temperature of 290 DEG C when the alloy has the best overall performance, microstructure is fine equiaxed grains, and at the same time there is no dynamic recrystallization grain strip completely, excellent mechanical properties, corrosion resistance, the hemolysis rate of 7.3%. maximum extrusion temperature of 290 DEG C when the extrusion ratio increases, reduce the performance of the micro alloy; Mg-3Sn-1Zn alloy in the extrusion temperature is 310 DEG -370 DEG, microstructure are equiaxed crystal, phase in Mg2Sn alloy matrix with uniform precipitation, with the increase of the extrusion ratio, the grain size, mechanical properties and corrosion resistance of.Mg-3Sn-1Zn-0.5Mn alloy decreased in the extrusion temperature is 310 DEG -370 DEG, microstructure of equiaxed crystal, with the The increase of the extrusion ratio, the grain size decreased, the mechanical properties and corrosion resistance increases. The hemolysis of different extrusion process of Mg-3Sn-1Zn alloy and Mg-3Sn-1Zn-0.5Mn alloy rate results, these two kinds of alloy extruded with the performance of a M G-3 Sn-1 Zn-0.5 Mn alloy is better than that of Mg-3Sn-1Zn alloy in the feasibility of adding.Mn element of the application environment of blood the mechanical properties, the Mn element can refine the Mg2Sn phase, improve the mechanical properties of materials. The same extrusion ratio and tensile strength increased by approximately 10-20MPa, elongation increased by approximately 2-6%: corrosion resistance, Mn element will reduce the adverse effect of impurity elements on magnesium alloy, when the alloy contains elements of Zn, add Mn the element can significantly reduce the corrosion rate of the material. The same extrusion of Mg-3Sn-1Zn alloy by -1.5V ~ -1.6V to Mg-3Sn-1Zn-0.5Mn alloy to the corrosion potential, corrosion Corrosion current speed decreases about 60% compared to the same period; hemolysis rate, the same ratio of Mg-3 Sn-1 hemolysis hemolytic extrusion of Zn-0.5Mn alloy was lower than that of Mg-3 Sn-1 Zn alloy.Mg-3Sn-1Zn-0.5Mn alloy microstructure evolution rate: 1) increasing the amount of deformation, the grain size shows decreasing trend of.2) Mg-3Sn-1Zn-0.5Mn alloy in solution without deformation, granular the Mn element along the grain boundaries, the extrusion deformation of precipitated Mg2Sn uniformly distributed in the alloy, the Mg2Sn phase is in the shape of disc shaped or rod-shaped.3) twin number decreases with the increase of deformation. When the deformation is small, the extrusion deformation of Mg-3Sn-1Zn-0.5Mn immiscible alloy in twin tissue morphology the change of twins after the change can occur from twin phenomena, and extrusion deformation will produce new twin, the number of twin twin twin back and new generation of little difference on the overall. The number of twin small changes; when the deformation is large, the phenomenon of increasing twin twin annealing of Mg-3Sn-1Zn-0.5Mn alloy, while the smaller grain size and more Mg2Sn phase also inhibited formation of deformation twins, the two together to make a sharp reduction in the number of twin.Mg-3Sn-1Zn-0.5Mn alloy deformation mechanism by slip and twinning, and dislocation movement the proliferation of dislocation tangles each other in the deformation process, as well as by pinning grain boundaries hinder the termination of movement; twin to grain is not conducive to the promotion of sliding plastic deformation, the deformation of deformation twinning and twin formation retreat simultaneously. When large deformation (extrusion ratio 64), grain size after the dynamic recrystallization is smaller, so that the grain boundary sliding mechanism plays an important role. The solution without deformation and deformation, twinning in Mg-3Sn-1Zn-0.5Mn alloy are {1012}1011 Solid solution without deformation twinning and growth mechanism of Mg-3Sn-1Zn-0.5Mn alloy {1012} twin twin dislocation mechanism of classical {1012}, small angle offset {1012} twin twin boundary surface; extrusion deformation of Mg-3Sn-1Zn-0.5Mn alloy {1012} the twin growth mechanism with disturbance mechanism, construction disturbance, auxiliary shear model of the twin interface straight. The {1012} interface is not in the {1012} twin plane, {1012} and twin misorientation angles are deviated from the theory of 86.3 degrees.

【学位授予单位】：哈尔滨工程大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG379

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