Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys > Magnesium

Study on Mechanical and Corrosion Properties of Megnesium-Zinc Based Alloys for Biomaterial

Author LiLei
Tutor GuanShaoKang
School Zhengzhou University
Course Materials Science
Keywords Magnesium - zinc base alloys Microstructure Mechanical Properties Corrosion resistance Simulated body fluid
CLC TG146.22
Type Master's thesis
Year 2009
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Biodegradable materials implanted organisms in the body constantly decomposition and decomposition products can be organism absorbed or excreted, has become the international front and hot in the field of biological material. Present in the bone implant material applied more biodegradable materials are mainly polymers such as poly lactic acid (PLA), poly-hydroxy acetic acid (PGA), the strength of these materials, however, is generally low, it is difficult to bear larger load, and the degradation product is acidic, easily causing inflammation. Magnesium and their alloys not only has good mechanical properties, but also non-toxic to the human body, the gradual degradation by corrosion in the body, and thus increasingly favored by people as a development potential of biodegradable implantable biological material. But existing magnesium alloy decline in the physiological environment the solution rate too fast, often not healed bone tissue lost due carrying capacity. So prepared both a certain mechanical properties, and magnesium alloy having a better corrosion resistance, and has a high practical value. In this paper, Mg-2.1 wt.% Of Zn-0.22wt.% Mn, Mg-2.1 wt% of Zn-0.22wt.? And Mg-1.99wt% Zn-0.17 wt.?-0.51wt% Si alloy is organized , mechanical properties and corrosion resistance research. The three alloys organization were α-Mg α-Mn, α-Mg Ca 2 Mg 6 Zn 3 and α-Mg of Mg < sub> 2 Si. Which of Mg-2.1Zn-0.22Ca alloy grain size of 85μm, the tensile strength of 172 MPa, elongation of 11%; the corrosion potential in simulated body fluid-1.71V, mass loss rate of 0.9 g / (cm 2 · year), mechanical properties and good corrosion. Microstructure of the alloy Mg-2Zn-xCa (x = 0.024wt.%, 0.022wt.%, 0.29wt.%, 0.46wt.%), Mechanical, corrosion resistance study results show that: with the Ca content increase the second phase Ca 2 Mg the Zn 3 content also increases, and at the grain boundaries are never continuous distribution to a continuous distribution, When the Ca content of 0.46wt.%, the second phase gathered at the grain boundaries, to form a coarse mesh structure; mechanical and corrosion resistance are first increased and then decreased rule, wherein the Mg-2.1Zn-0.22Ca alloy better mechanical and corrosion resistance. Guarantee corrosion resistance under the conditions, in order to further improve the performance of the alloy, the of Mg-2.1Zn-0.22Ca alloy heat treatment of different process conditions, microstructure, mechanical properties of the alloys after heat treatment , corrosion resistance of the study results show that: under the same temperature conditions, with the extension of the holding time, the second phase Ca 2 Mg 6 Zn 3 gradually reduced, and the solid solution and the second phase increases; in the same holding time, as the heat treatment temperature increases, second phase Ca 2 Mg 6 < / sub> Zn 3 is decreasing. With the holding time, the tensile properties of the alloy appear first increase, and then a downward trend, wherein the solid solution treatment at 360 ℃ 4h to obtain the mechanical properties of the alloy is preferably, a tensile strength of 210MPa and an elongation 21%, compared to the same cast alloy, the tensile strength increased by 24%, 90% increase in elongation. Electrochemical corrosion of the alloy corrosion resistance under different heat treatment conditions. The results show that: the same heat treatment temperature increases as the holding time, and the same incubation time with the heat treatment temperature, the alloy corrosion resistance decreased slightly; weight loss test and pH testing also confirmed this variation. The potential of the alloy after heat treatment is is overall relatively close between the between-1.83V to-1.75V little difference compared with cast alloy corrosion. Test confirmed: by a heat treatment to improve the mechanical properties of the alloy, while the energy and no significant reduction in the corrosion resistance of the alloy. The same solution treatment at 360 ℃ heat 4h best for of Mg-2.16Zn-0.29Ca and Mg-2.06Zn-0.46Ca, alloy, the the alloy Mg the-2.1Zn-0.22Ca the mechanical properties and corrosion resistance, has good overall performance. This article is based biomedical biodegradable materials, the mechanical properties and corrosion resistance can match of Mg-2.1Zn-0.22Ca alloy, alloy composition and heat treatment process optimization, to further study the biocompatibility and as implanted body laid the foundation.

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