液氮球磨制备Al-Zn-Mg-Cu纳米晶粉末及组织分析

Synthesis and microstructure of nanocrystalline Al-Zn-Mg-Cu alloy powders by cryomilling

利用液氮球磨技术制备了Al-Zn-Mg-Cu纳米合金粉末.采用X射线衍射对材料在球磨过程中的固态相变、晶粒尺寸和微观应变进行了研究,利用金相显微镜和透射电镜观察了微观组织.研究表明,随着球磨的进行,雾化粉末中的MgZn2第二相逐步减少,并最终完全超饱和固溶于α-Al之中.低速(200r·min-1)球磨10h后仍有少部分粗晶存在于粉末心部;高速(400r·min-1)球磨能够使粉末纳米晶粒更加均匀.材料经过低速液氮球磨6h以后平均晶粒大小稳定在45nm,并保持到10h不再变化;增加主轴转速到400r·min-1继续球磨5h后,粉末平均晶粒大小降到34nm.微观应变随着球磨进行呈现先增大后降低的趋势.

A nanocrystalline Al-Zn-Mg-Cu alloy was synthesized by mechanically milling at cryogenic temperature （cryomilling）. The effect of cryomilling process on the microsturcture, phase transformation in solid, grain size and microstrain of this alloy was investigated by X-ray diffraction （XRD）, optical microscopy （OM） and transmission electron microscopy （TEM）. During the cryomilling, the second phase MgZn2 was gradually disappeared and ultimately super-saturated to α-A1. With increasing milling time, the grain size of the alloy decreased sharply. Howerver there were still a few coase grains in the core of powders after low-speed （200 r· min^-1） cryomilling for 10 h. Contrastively, high speed （400 r· min^-1） cryomilling could result in more uniform nanometer grains. According to the XRD results, the average grain size was 45 nm after low speed cryomilling for 6 h and kept stable until 10 h, but the average grain size reduced to 34 nm after farther high speed cryomilling for 5 h. The microstrain increased gradually to a maximum, and then fell off along the milling processing.