【作者】 边丽萍；

【导师】 梁伟；

【作者基本信息】 太原理工大学 ， 材料加工工程， 2004， 硕士

【摘要】 金属纳米材料具有独特的组织结构和物理、力学及化学性能，应用潜力极大，受到科学界的普遍关注。本文采用机械研磨法合成了镁基合金，并通过等通道转角挤压制备了纯铝及Al-3％Cu合金的超细晶块体材料。 通过将Mg、Al、Ti元素粉末混以聚乙烯乙二醇进行研磨的机械化学研磨法合成了Mg-5w％Al-10.3w％Ti镁基纳米合金。与常规粉末冶金法相比，该法合成的材料力学性能呈现出奇异的应变软化现象。透射电子显微镜分析表明，合金晶粒尺寸大多为20～30nm，个别晶粒的尺寸约为90nm；此外，观察到许多直径约3～7nm的纳米管。 采用等通道转角挤压(ECAE／ECAP)法对纯铝及Al-3％Cu合金进行挤压，对挤压过程中的组织演变规律，力学性能、组织稳定性以及影响组织演变的因素等进行了研究。结果表明，用ECAP技术将纯铝从初始晶粒尺寸约1.0mm细化到0.48μm； 太原理工大学硕士学位论文8次挤压后晶粒细化达到饱和，硬度达到最大，在150OC退火lh后组织保持稳定;相对于未挤压试样，14次挤压试样经5%压缩后呈现出高的屈服强度和加工硬化速率;低温挤压加快晶粒细化，4次挤压后即形成大角度晶界分割的等轴状晶粒。对Al一3%Cu合金在固溶态和时效态进行了ECAP挤压。透射电镜观察和硬度测试结果表明，单相固溶体在挤压后存在大量共格的析出相颗粒，其晶粒细化效果不如双相合金明显。时效合金中大量非共格析出相颗粒的存在加快ECAP晶粒细化，提高加工硬化速率。更多还原

【Abstract】 Nanostructured metallic materials attract great attention from scientific research field due to their peculiar microstructures and physical, mechanical and chemical properties and the great potential for practical applications. In this paper, nanostructured Mg-5w%Al-10.3w%Ti alloy has been fabricated by mechanical alloying and ultrafme-grained bulk pure Al and Al-3%Cu alloy by equal channel angular pressing(ECAP).Nanostructured Mg-5w%Al-10.3w%Ti alloy was prepared by mechanical alloying with the powder mixture of Mg. Al, Ti and process control agent of polyethylene-glycol (H(OCH2CH2)nOH). Compared to conventional powder metallurgy, the mechanical property of the sample synthesized by mechanical alloying shows peculiar strain-softening. TEM analysis shows that the average grain size of the alloy is 20-30nm. Besides, several grains about 90nm and many nanotubes about 3~7nm in diameter are observed.ECAP experiments were conducted on pure Al and Al-3%Cu alloy. The microstructural evolution during ECAP and the influence factors, mechanichal property and the stability of the microstructure of pure Al and Al-3%Cu were investigated. The pure Al was refined from 1.0mm to 0.48μm by ECAP. The refinement saturated after EGA Pressing for 8 passes, corresponding to a maximum hardness value. It was found that such a refined microstructure is stable even after annealing at 150℃ for 1 h. The conventional compression test showed that the as-ECA Pressed sample exhibits a much higher yield strength and a higher strain hardening rate than the unECA Pressed sample. Decreasingtemperature of EGA pressing in pure Al promotes the refinement. Equiaxed grains with high angle grain boundaries are obtained just for 4 passes by EGA Pressing at the lower temperature, in contrast to 8 passes at room temperature. Al-3%Cu alloys as-solid-solutioned and as-aged are subjected to EGA Pressing. The results of TEM analysis and hardness test showed that quantities of coherent particles precipitated in the single-phase solid solution after ECAP for 6 passes, however, its refinement effect is not as significant as that of two-phase alloy after equal passes, in which a large number of incoherent precipitates promote the refinement of ECAP and the strain hardening rate.更多还原