【作者】 黄婷；

【导师】 杨林； 林立；

【作者基本信息】 沈阳工业大学 ， 材料学， 2012， 硕士

【摘要】 随着科技的快速发展,各个领域都在不断的探索和研发具备良好综合性能的材料。镁合金因其低密度、高的比强度和比刚度及其易于回收再利用等优良性能而成为研究领域的首选材料。AZ91镁合金除具备上述性能外,其价格低廉及具有良好的铸造性能,而成为常用的商业化镁合金。经塑性变形后的变形镁合金比铸造镁合金具有更优异的性能。本实验对经固溶处理后的AZ91镁合金进行室温压缩变形,然后再进行退火处理。利用扫描电镜、能谱仪、X-射线衍射仪等对其微观组织形貌、成分、结构及相组成进行分析,采用布洛维硬度计和数显显微硬度计从宏观及微观上对AZ91镁合金硬度进行分析,以研究室温压缩对AZ91镁合金微观组织和性能的影响,进一步研究退火对变形后合金显微组织、性能的影响及退火后变形和未变形AZ91镁合金β-Mg₁₇Al₁₂相析出动力学。实验结果表明:AZ91镁合金在室温压缩过程产生了大量孪晶,其中有很多交叉孪晶的交叉角度接近于90o;大量孪晶的存在为β-Mg₁₇Al₁₂相的析出提供了形核基底,也为静态再结晶提供了有利的形核条件;退火过程中β-Mg₁₇Al₁₂相优先沿晶界、孪晶界析出,尤其易在孪晶与晶界、孪晶交接处析出并长大;250℃退火时,随退火时间的延长,孪晶界逐渐变宽,同时析出相的排列与基体具有一定的方向性;变形量为8%时,试验退火条件下合金未发生再结晶;当变形量为10%时,在350℃退火时则发生明显静态再结晶;在250³50℃退火时,AZ91镁合金析出β-Mg₁₇Al₁₂相的激活能为23.8³7.9kJ/mol;退火后材料的硬度值受形变量、析出物数量、退火时间及其温度等因素影响,发生了很大变化。更多还原

【Abstract】 Many fields have been looking for materials with better comprehensive properties. Magnesium alloy is the first choice with its excellent compreshensive property, such as low density, high specific strength and specific stiffness and easy recycle, etc. AZ91alloy is a commonly commercialized magnesium alloy, owing to his low cost and an excellent combination property. It is well known that magnesium alloy has a higher comprehensive properties after plastic deformation after being deformed.In this paper, the experimental samples are subjected to solution treatment, compression processing at room temperature and annealing. The microstructure, chemical compositions, rock-well hardness and micro-hardness of solid-solution, solution + compression, solution + compression + annealing AZ91 alloy were investigated by using scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS）, X-ray diffraction （XRD）, rock-well hardness and micro-hardness tester, respectively. And precipitation kinetics ofβ-Mg₁₇Al₁₂ phase in deformed and non-deformed AZ91 alloys after annealing were also studied.The results shown that lots of twining would emerge as a result of compression at room temperature, most of which intersect with respect to each other at near 90o, serving as beneficial nucleation condition both forβ-Mg₁₇Al₁₂ phase precipitation and static recrystallzation. Theβ-Mg₁₇Al₁₂ phase precipitated preferentially at twin and grain bounbaries. In the annealing process, phase precipitation and growth were frequently observed at the intersection between twinning and original grain, or among various twinnings. The twin boundaries will get wider gradually with longer aging time and increasing temperature; Meanwhile, certain orientation relationships were also discovered between theβ-Mg₁₇Al₁₂ phase precipitated in twinning and theα-Mg matrix under 250℃annealing.When the deformation was 8%, no recrystallzation occurred under （250³50）℃×2h annealing condition. When the deformed to 10%, static recrystallzation started considerably after annealing at 350℃. The activation energy forβ-Mg₁₇Al₁₂ phase precipitation in AZ91 alloy was calculated to be 23.8³7.9kJ/mol using the JMAK equation, in accordance with our experimental data. The hardness of AZ91 alloy can be greatly related to compressing rate, precipitate amount, annealing temperature and time, etc.更多还原