Effects of hot pressing temperature and annealing temperature on microstructure and compressive properties of a bulk nanocrystalline AZ61 magnesium alloy contain Ti-猫眼课题宝

热压温度和退火温度对含Ti块体纳米晶AZ61镁合金显微组织和压缩性能的影响

DOI：

10.1016/j.jallcom.2021.161533

发表时间：

2021-08

期刊：

JOURNAL OF ALLOYS AND COMPOUNDS

影响因子：

6.2

通讯作者：

中科院分区：

材料科学2区

文献类型：

作者：

Huan Yu;Jixue Zhou;Rongrong Wang;Qian Su;Suqing Zhang;Jianhua Wu;Wang Xin;Lianxi Hu

在无稀土镁合金中，发展纳米晶基体组织和弥散稳定的纳米级析出相是实现超高强度的关键，也是一个巨大的挑战。采用机械球磨和真空热压的方法制备了块体纳米晶镁合金。分析了热压温度对陶瓷组织、致密化和力学性能的影响。在723 K热压60 min后，粉末得到致密化，镁基体的平均晶粒尺寸约为76 nm。用X射线衍射仪和高分辨电子显微镜检测到了粒径约为10 nm的纳米Ti 3Al析出相。之后，在573 K下进行不同时间的退火处理。强度和塑性都有明显提高。在573 K退火80 h后，屈服强度、压缩强度、断裂应变和硬度分别为498 MPa、553 MPa、4.9%和1.44 GPa。在强化机理分析的基础上，计算出晶界强化效应、Orowan效应和载荷传递效应的贡献率分别为64%、33%和3%。结果表明，纳米晶镁相和纳米级Ti 3Al析出相是实现超高强度的关键。

Involving rare-earth-free Mg alloys, developing microstructure of nanocrystalline matrix and dispersing stable nano-scale precipitates, being a great challenge, is the key to achieve ultra-high strength. In this work, bulk nanocrystalline magnesium alloy was prepared by mechanical milling and subsequent vacuum hot pressing. The effect of hot pressing temperature on microstructure, densification and mechanical properties was analyzed. After hot pressing at 723 K for 60 min, the powders got densified and the average grain size of magnesium matrix was ~76 nm. Nano-scale Ti3Al precipitates with a particle size of ~10 nm were detected by X-ray diffractometer and high-resolution electron microscope. After that, annealing treatment was carried out at 573 K for various times. Both strength and ductility got improved evidently. After annealing at 573 K for 80 h, the yield strength, compressive strength, fracture strain and hardness were 498 MPa, 553 MPa, 4.9% and 1.44 GPa, respectively. Based on analysis on strengthening mechanisms, the contribution rates owing to grain boundary strengthening effect, Orowan effect and load transfer effect were calculated to be 64%, 33% and 3%. It was certified that nanocrystalline magnesium phase together with nano-scale Ti3Al precipitates play a crucial role in realizing ultra-high strength.