低碳钢超声喷丸表面纳米化的研究

NVESTIGATION OF SURFACE NANOCRYSTALLIZATION OF A LOW CARBON STEEL INDUCED BY ULTRASONIC SHOT PEENING

利用超声喷丸技术在 ２０低碳钢上制备出具有纳米晶体结构特征的表面层，利用 Ｘ射线衍射及电镜分析研究了表面纳米层的微观组织结构特征结果表明，经超声喷丸处理可使样品表层晶粒细化至纳米量级表层晶粒尺寸约为 １０ ｕｍ，微观应变为０．０２％－０．０４％．表面纳米层厚度约为１０μｍ．另外，样品表层亚稳相 Ｆｅ３Ｃ发生分解，形成纳米尺寸的石墨相和α－Ｆｅ相．

A nanocrystalline surface layer was fabricated on a 20 steel plate by using an ultrasonic shot peening (USSP) technique. The USSP induced surface nanocrystallization products were characterized by means of XRD and TEM. Experimental evidences showed that after the USSP treatment for a short period of time, the initial coarse-grained structure in the top surface layer was refined into ultrafine grains. The mean grain size in the surface layer is about 10 um and the mean microstrain about 0.02%-0.04%. The thickness of the nanocrystalline surface layer is about 10 pm, which is dependent on the treatment duration. It was also found that the metastable phase Fe3C in the surface layer decomposes into nanometer-sized graphite and α-Fe phases after the USSP treatment.