低温球磨制备高热稳定性纳米晶Al-Zn-Mg-Cu合金块体材料

Preparation of bulk nanocrystalline Al-Zn-Mg-Cu alloy with high thermal stability by cryomilling

利用液氮球磨和真空热压技术制备纳米晶Al-10Zn-3Mg-1.8Cu(质量分数,%)合金块体材料。采用X射线衍射(XRD)和透射电镜(TEM)对材料在制备过程中的固态相变、晶粒尺寸和热稳定性进行分析。结果表明,材料经过液氮球磨15 h后晶粒尺寸为37 nm,真空热压后材料晶粒保持在100 nm,热挤压后晶粒尺寸约为300 nm,热处理后晶粒尺寸保持不变。材料的高热稳定性原因在于大量合金元素和杂质元素超饱和固溶于Al基体中阻止了晶粒的长大,以及细小析出MgZn2相和Al2O3颗粒对于晶界的钉扎作用。

The preparation of bulk nanocrystalline Al-10Zn-3Mg-1.8Cu （mass fraction,%） alloy by mechanically milling at cryogenic temperature （cryomilling） and hot pressing in vacuum was studied. By X-ray diffraction （XRD） and transmission electron microscopy （TEM）, the effects of cryomilling process on the phase transformations in solid, the grain size and the thermal stability for this alloy were investigated. The results show that the grain size of the as-atomized Al-Zn-Mg-Cu alloy powder is gradually reduced and approaches 37 nm after 15 h cryomilling. The average grain size reaches about 100 nm after hot pressing in vacuum. After hot extrusion and heat treatment, the grains grow to about 300 nm. The results obtained herein suggest that the significant thermal stability of the bulk nanocrystalline Al-Zn-Mg-Cu alloy may be attributed to the solute drag of the alloy elements and the impurity elements, which can prevent the grain growth. And more, the zener pinning from grain boundary of the nano-scale Al2O3 arising from cryomilling and the fine MgZn2 phase also play an important role.