摘要
采用低温球磨、热等静压和挤压等工艺制备了块体纳米晶7050铝合金。分别利用透射电镜（TEM）和扫描电镜（SEM）对制备铝合金的微观组织和断口形貌进行了观察,并对该铝合金的化学成分、密度、硬度和拉伸性能进行了测定。结果表明,制备的块体纳米晶7050铝合金的平均晶粒尺寸为100-200 nm,密度为2.76 g/cm^3,HV显微硬度为1184 MPa。抗拉强度和延伸率分别为412 MPa和5.2%。经时效处理后,材料的拉伸性能虽有所提高,但仍低于传统7050铝合金。分析认为,由于雾化参数和球磨参数的选取欠合理,导致了薄片状粉体的产生。而薄片状的形貌又使得粉体不能有效充填包套,最终得到的块体材料致密度低,内部缺陷较多。这些缺陷使得块体材料内部的晶粒（或颗粒）之间形成弱界面连接,降低了材料的拉伸性能。
The combination of three processing routes including cryomilling, hot isostatic pressing（HIP） and hot extrusion was used for fabrication of bulk nanocrystalline Al 7050. The microstructure and fractography of the material were observed by transmission electron microscopy（TEM） and scanning electron microscopy（SEM）. Furthermore, the chemical composition, density, microhardness and tensile properties of the material were also measured. Results show that the average grain size of the bulk nanocrystalline Al 7050 ranges from 100 nm to 200 nm. The density and HV microhardness of the material are 2.76 g/cm^3 and 1184 MPa, respectively. The resulted sample exhibits ultimate strength of 412 MPa with an elongation of 5.2%. After ageing treatment, the ultimate strength and elongation of the material increase by 1.21% and 50%, respectively, which are still lower than that of the conventional Al 7050. The results suggest that improper selected starting powder and milling parameters result in the flake-like morphology of the cryomilled powder. The flake-like morphology makes it difficult for the cryomilled powder to fill the can entirely and to achieve a high density material, which lead to the weak interface within the bulk material and in turn degrade the mechanical properties of the bulk nanocrystalline Al 7050 prepared in the present work.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2015年第1期152-157,共6页
Rare Metal Materials and Engineering
