搅拌摩擦加工态生物Mg-Zn-Y-Nd合金厚板的组织与性能

发布时间：2018-03-16 03:17

本文选题：Mg-Zn-Y-Nd合金　切入点：厚板　出处：《郑州大学》2017年硕士论文　论文类型：学位论文

【摘要】：镁合金具有可降解、优良的生物相容性和力学相容性等特点,成为新一代最具发展潜力的生物医用金属材料。但镁合金在临床应用中一直存在着两大难题:力学性能较低和降解速率过快且不均匀。搅拌摩擦加工技术(Friction stir processing,FSP)能够有效细化镁合金晶粒和组织中的第二相,从而提高其综合性能,改变腐蚀机制,实现均匀腐蚀。目前研究中受搅拌头尺寸的限制,获得的改性区域的尺寸较小,无法得到有效的利用。本文选用搅拌针长度为10mm的搅拌头对生物镁合金厚板进行搅拌摩擦加工,但单面搅拌摩擦加工时由于在板材厚度方向上存在温度梯度,造成加工区域组织不均匀,因此,进一步采用双面搅拌摩擦加工技术对其进行加工,以获得综合性能较好的大尺寸改性区域,且使合金能够均匀降解。本文采用金相分析、扫描电镜分析、显微硬度测试、拉伸实验、电化学测试、析氢测试及失重分析等方法,研究单面和双面搅拌摩擦加工后Mg-Zn-Y-Nd合金厚板的微观组织、力学性能和在模拟体液中的耐腐蚀性能,探讨搅拌摩擦加工工艺对生物Mg-Zn-Y-Nd合金厚板组织和性能的影响规律。均匀化退火态Mg-Zn-Y-Nd合金厚板经单面搅拌摩擦加工后搅拌区可细分为上部搅拌区、中部搅拌区和下部搅拌区,搅拌区的上部、中部和下部的平均晶粒尺寸逐渐减小,分别为5.48μm、4.75μm和3.80μm。随着旋转速度和前进速度的改变,搅拌区各区域的组织演变规律不同,难以获得组织均匀的搅拌区。这主要是由于镁合金厚板在搅拌摩擦加工过程中沿板材厚度方向上存在温度梯度,热和机械搅拌作用自上而下逐渐减小,导致加工区域组织沿厚度方向上不均匀。双面搅拌摩擦加工合金搅拌区的上部、中部和下部的平均晶粒尺寸分别由单面搅拌摩擦加工合金的5.30μm、5.08μm和4.45μm细化至3.93μm、3.20μm和3.19μm,且第二相颗粒尺寸细小,分布均匀。搅拌摩擦加工合金的硬度值面分布与组织分布一致。双面搅拌摩擦加工合金搅拌区各层的抗拉强度和伸长率均高于单面搅拌摩擦加工合金,其中下层搅拌区的抗拉强度和伸长率最高,分别为283.3MPa和23.9%。搅拌摩擦加工后合金在模拟体液中的耐腐蚀性能较均匀化退火态合金明显提高,且双面搅拌摩擦加工合金在模拟体液中的耐腐蚀性能最好,其腐蚀方式由点蚀变为均匀腐蚀。
[Abstract]:Magnesium alloys have the characteristics of biodegradability, excellent biocompatibility and mechanical compatibility. Magnesium alloys have become the most promising biomedical metal materials in the new generation. However, there are two problems in clinical application: low mechanical properties and fast and uneven degradation rate. Friction stir stir processing (FSP). It can refine the grain and the second phase in the microstructure of magnesium alloy effectively. In order to improve its comprehensive performance, change the corrosion mechanism, and achieve uniform corrosion. In the present research, the size of the modified area is smaller because of the restriction of the size of the mixing head. It can not be used effectively. In this paper, the thick plate of biological magnesium alloy is processed by friction stir with a stirring head of 10 mm in length, but the temperature gradient exists in the direction of the thickness of the plate during the single side friction stir processing. As a result of the uneven structure of the processing area, the double-side friction stir processing technology is further adopted to obtain the large modified area with better comprehensive properties and the alloy can be degraded uniformly. In this paper, metallographic analysis is used. Scanning electron microscopy (SEM), microhardness test, tensile test, electrochemical test, hydrogen evolution test and weightlessness analysis were used to study the microstructure of Mg-Zn-Y-Nd alloy thick plate after single and double side friction stir processing. Mechanical properties and corrosion resistance in simulated body fluids, The effect of friction stir processing technology on the microstructure and properties of thick Mg-Zn-Y-Nd alloy plate was discussed. The stir zone of Mg-Zn-Y-Nd alloy thick plate in homogenized annealed state can be subdivided into upper stir zone, middle stir zone and lower stirring zone after single side friction stir processing. The average grain size of the upper, middle and lower parts of the mixing zone gradually decreased to 5.48 渭 m 4.75 渭 m and 3.80 渭 m, respectively. It is difficult to obtain homogeneous stirring zone, which is mainly due to the existence of temperature gradient along the thickness direction of magnesium alloy thick plate during friction stir processing, and the effect of heat and mechanical stirring gradually decreases from top to bottom. The microstructure of the processing area is not uniform in the direction of thickness. The upper part of the alloy stir zone in the double-sided friction stir processing, The average grain sizes of the middle and lower parts of the FSW alloy were refined from 5.30 渭 m and 4.45 渭 m to 3.93 渭 m, 3.20 渭 m and 3.19 渭 m, respectively, and the size of the second phase was fine. The distribution of hardness value plane of friction stir processing alloy is consistent with that of microstructure. The tensile strength and elongation of each layer in the stir zone of double side friction stir processing alloy are higher than that of single side friction stir processing alloy. The tensile strength and elongation of the lower stirring zone are the highest, 283.3 MPA and 23.9 MPA, respectively. The corrosion resistance of the alloy in the simulated body fluid after friction stir processing is obviously improved than that of the homogenized annealed alloy. The corrosion resistance of the alloy is the best in the simulated body fluid, and the corrosion mode of the alloy changed from pitting to uniform corrosion.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22;TG453.9

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