电子束对稀土铝硅合金表面形貌及硬度的影响

Effects of HCPEB on Morphology and Hardness of Al-Si Alloy with Rare Earth Element

目的利用强流脉冲电子束改性Al-17.5Si-0.3Nd合金表面,提高合金表面的显微硬度。方法通过场发射扫描电镜(FESEM)、电子探针(EPMA)、X射线衍射仪(XRD)以及维氏显微硬度计等一系列先进的检测手段,对改性后合金表面的微观形貌和性能变化进行研究。结果 SEM以及EPMA分析结果显示强流脉冲电子束处理后,合金表面形成了铝基体以及无微裂纹的晕圈结构,并且改性后合金表面上各种元素分布均匀。XRD结果显示强流脉冲电子束处理后,合金表面无新相形成,所有衍射峰发生了宽化以及偏移现象。随着脉冲次数的增加,衍射峰先向高角度偏移,后向低角度偏移。其中,5次脉冲试样的偏移角度最大。另外,显微硬度测试结果显示,铝基体的硬度随脉冲次数增加而递增,硬度值由原始样品的534.95 MPa增加到25次脉冲的1258.59 MPa;相对地,晕圈组织的硬度随脉冲次数的增加而递减,硬度值由原始样品的10 067.7 MPa下降到25次脉冲的1390.29 MPa。结论强流脉冲电子束改性后的合金表面晶粒细化显著,表面硬度总体上有所提高。

The work aims to improve microhardness of Al-17.5Si-0.3Nd alloy surface by modifying the surface with high current pulsed electron beam （HCPEB）. Changes in surface morphology and performance of HCPEB-modified alloy were studied with FESEM, EPMA, XRD, and Vickers hardness tester. SEM and EPMA analysis results revealed that A1 substrate and microerack-free halo structure were generated on the surface of HCPEB-treated alloy, and all elements on the alloy surface were distributed uniformly in modified layer. XRD analysis results showed that no new phase was formed after HCPEB treatment, and all diffraction peaks broadened and shifted. Diffraction peaks firstly moved toward high angle and then toward low angle as pulse numbers increased. The largest shift angle was present in the sample treated with 5 pulses. In addition, microhardness test results demonstrated that microhardness ofAl substrate increased from 534.95 MPa （for initial sample） to 1258.59 MPa （sample treated with 25 pulses） as pulse number increased, while microhardness of the halo microstructure sharply decreased from 10067.7 MPa （for initial sample） to 1390.29 MPa （sample treated with 25 pulses） as pulse number increased. The grains of alloy surface are markedly refined after HCPEB modification, and surface hardness of alloy surface is increased as a whole.