【作者】 张大伟；

【导师】 王德庆；

【作者基本信息】 大连交通大学 ， 材料学， 2009， 硕士

【摘要】 采用低温球磨结合真空热压烧结技术制备了块体纳米Al晶体材料,并加入硬质Al2O3颗粒来进一步提高该材料的强度和硬度。利用X射线衍射以及透射电镜对材料的微观组织进行了分析和观察,对所制备块体纳米材料的密度、显微硬度和拉伸性能进行了测定。研究结果表明,当球磨时间从8 h增加到14 h时,纳米Al粉末颗粒的晶粒尺寸从55 nm减小到43 nm,微观应变从0.0272 %增至0.0759 %。经致密化处理后,该材料的晶粒尺寸从115 nm减小到71 nm。热挤压后的块体纳米Al及Al-Al2O3晶体材料的相对密度都达99.4 %以上。其中,两种材料的最高显微硬度分别为1.02和1.22 GPa,比粗晶Al的显微硬度分别提高了3和3.6倍。块体纳米Al的最高屈服和抗拉强度分别为165和243 MPa,比粗晶1050纯Al的屈服和抗拉强度分别提高了7.5和3.2倍。块体纳米Al-Al2O3的最高和抗拉强度分别为242和305 MPa,比在相同工艺条件下制备的块体纳米Al分别提高了47和20 %。当平均晶粒尺寸小于223 nm时,块体纳米Al晶体材料的屈服强度与晶粒尺寸之间的关系为σ’= 71.8 + 1.8D?1/2。块体纳米Al的最大弹性模量为71.8 GPa,比粗晶Al的弹性模量提高了4 %。在相同工艺条件下,块体纳米Al-Al2O3的最大弹性模量为76.8 GPa,比块体纳米Al提高了7 %。块体纳米Al及Al-Al2O3晶体材料的最小延伸率分别为6.4和5.8 %,只有粗晶Al延伸率的16和15 %。两种材料的相对密度、显微硬度、强度以及弹性模量均随着晶粒尺寸的减小而增大,而延伸率随着晶粒尺寸的减小逐渐减小。更多还原

【Abstract】 Bulk nanocrystalline Al are fabricated by cryomilling, compacting, vacuum sintering and extrusion with hard particle addition to improve the strength and hardness of the material. Microstructure of the materials are observed and analyzed by TEM and XRD. Density, microhardness and tensile property of the materials are measured. Experiment results demonstrate that grain size of the aluminum powder is reduced from 55 to 43 nm, and microstrain of the crystalline materials is increased from 0.0272 to 0.0759 % when the cryomilling time is increaseed from 8 to 14 h. Grain sizes of the bulk nanocrystalline Al is reduced from 115 to 71 nm. The relative densities of the bulk nano Al and Al-Al2O3 crystalline materials are more than 99.4 % after hot extrusion. The maximum microhardness of the two kinds material are 1.02 and 1.22 GPa, which are 3.0 and 3.6 times higher than that of coarse-grained Al. The maximum yield and tensile stress of the bulk nano Al reach 165 and 243 MPa which are 7.5 and 3.2 times higher than that of commercial 1050 pure aluminum. The maximum yield and tensile stress of the bulk nano Al-Al2O3 reach 242 and 305 MPa which have a 47 and 20 % stress of increase compared with the bulk nano Al under the same processing condition. When the grain size is below 223 nm, the relationship between yield stress and grain size of the bulk nano Al material is expressed asσ’= 71.8 + 1.8D?1/2. The maximum elastic mould of the bulk nano Al is 71.8 GPa which is 4 % improvement on the elastic mould of the coarse-grained Al. Under the same processing condition, the maximum elastic mould of the bulk Al-Al2O3 is 76.8 GPa which is 7 % improvement on the elastic mould of the bulk nano Al. The minimum elongations of the bulk nano Al and Al-Al2O3 crystalline materials are 6.4 and 5.8 % which account for 16 and 15 % of he coarse-grained Al. The relative densities, microhardness, strength and elastic mould of the two kinds of material are increased with reducing of grain size, but the elongations are decreased.更多还原