采用粉末冶金技术制备块体超细晶Mg-3A1-Zn合金.首先采用球磨Mg、Al、Zn混合粉末来制备纳米晶粉末,所得的粉末的平均晶粒尺寸为45 nm.随后将球磨好的粉末封入铝包套内,分别在室温和633 K温度下,在真空烧结炉内进行真空热压.然后将烧结后的样品在423 K下挤压以进行进一步的致密化处理.结果表明:致密后的冷压样品的晶粒尺寸为180 nm,而热压坯的晶粒尺寸为600 nm,冷压样品的屈服强度达464 MPa;超细晶镁合金的强化机制主要是细晶强化,这主要是由于HCP结构的材料晶粒尺寸对材料的影响更为明显.固化后冷压样品的最终密度为(1.777±0.006) g/cm3,而热压样品的最终密度为(1.800±0.006) g/cm3.
Powder metallurgy was used to fabricate a bulk ultrafine grain size (UFG) Mg-3Al-Zn alloys.Nanocrystalline alloy powders with an average grain size of 45 nm were synthesized via ball milling of elemental powders of Mg,Al and Zn.The milled powders canned in Al containers were subjected to cold (at room temperature) or hot press (for 40 min at 633K),respectively,in a vacuum furnace.The sintered samples were extruded at 423 K to further solidify.The results show that the average grain size is 180 nm for the cold samples,and that is 600 nm for the hot samples.The cold-press alloys show a yield stress of 426 MPa.The high strength of UFG Mg is attributed to the fine grain strengthening mechanism resulting from the strong dependence of strength on the grain size for HCP metals.The consolidated samples of the cold-press and hot-press alloys have a final density of (1.777±0.006) and (1.800±0.006) g/cm3,respectively.