一种新型Al-2.5GNPs细化剂制备及其对AZ31镁合金的细化作用

Preparation of a Novel Al-2.5GNPs Refiner and its Refining Effect on AZ31 Magnesium Alloy

镁合金因自身强度低和塑性较差限制了其在工业领域的应用,向镁合金中添加晶粒细化剂的方法能够改善其组织并提高材料的强度和塑性,是提升镁合金性能的最有效方法之一。本文利用球磨工艺结合粉末冶金的方法制备出一种含有GNPs(石墨烯纳米片)的新型镁合金细化剂。采用拉曼光谱分析法探究了不同球磨参数对GNPs的质量影响规律,得出较优球磨工艺参数为:转速300 r/min、球磨时间2 h,可以保证球磨后GNPs的高质量。将其混合粉体进行冷压,并在400℃烧结2 h,得到含有GNPs且组织致密、成型良好的Al-2.5GNPs细化剂。采用OM、SEM、XRD、TEM等表征手段初步分析了细化剂中Al4C3和GNPs对AZ31镁合金中的细化及强化机理。在720℃下加入质量分数为1.5%的Al-2.5GNPs细化剂,可以使AZ31镁合金的晶粒尺寸从228.8μm细化至65.6μm,抗拉强度从112.6 MPa提升至178.2 MPa,伸长率从8.9%提升至16.7%,分别提高了58.3%和87.6%。

The industrial application of magnesium alloys is limited by their low strength and poor plasticity.The addition of grain refiners to magnesium alloys can improve their microstructure,strength and plasticity,which is one of the most effective methods for improving their properties.In this paper,a refiner containing GNPs(graphene nanosheets)was prepared by ball milling and powder metallurgy.Raman spectroscopy was used to preliminarily explore the influence of different ball milling parameters on the quality of the GNPs,and the relative optimal ball milling parameters were 300 r/min and 2 h,which ensured the high quality of the GNPs after ball milling.The composite powder was cold pressed and sintered at 400℃×2 h to obtain a well-formed Al-2.5GNPs refiner containing a GNP phase with a dense structure.The binding situation of the mixed powder and the refinement and strengthening mechanism of Al4C3 and the GNPs in the AZ31 magnesium alloy were preliminarily analysed using OM,SEM,XRD and TEM characterization methods.By adding a 1.5 wt.%Al-2.5GNPs refiner at 720℃,the grain size of the AZ31 magnesium alloy decreases from 228.8μm to 65.6μm,the tensile strength increases from 112.6 MPa to 178.2 MPa,and the elongation increases from 8.9%to 16.7%,increasing by 58.3%and 87.6%,respectively.