ABSTRACT

Severe plastic deformation of 304L stainless steel plate was carried out by friction stirring under an isothermal tool temperature at 825°C. The friction stirred zone showed extensive grain refinement, high fraction of low angle grain boundaries due to dislocation rearrangement, Σ3 and Σ9 special grain boundaries and discrete Fe–Cr–Mn-rich particles. Electrochemical polarisation measurements were done on the base metal (BM) and friction stir welded (FSW) specimens in the neutral and acidified 3.5% NaCl solutions. The BM showed marginally better pitting resistance in the neutral chloride solution than the FSW because of a larger fraction of special grain boundaries, and larger grain size. Whereas in acidified 3.5% NaCl solution, the FSW showed better corrosion resistance than the BM. The surface film of the FSW had a lower impedance and a lower defect concentration than the BM indicating higher diffusivity of point defects in the FSW.

摘要

304L不锈钢板在825℃等温工具温度下通过摩擦搅拌进行剧烈塑性变形。摩擦搅拌区表现出广泛的晶粒细化，由于位错重排，Σ3和Σ9特殊晶界和离散的富Fe-Cr-Mn颗粒的低角度晶界比例很高。在中性和酸化的 3.5% NaCl 溶液中对贱金属 (BM) 和搅拌摩擦焊接 (FSW) 试样进行电化学极化测量。BM 在中性氯化物溶液中表现出比 FSW 稍好一点的抗点蚀性，这是因为特殊晶界的比例更大，晶粒尺寸更大。而在酸化的 3.5% NaCl 溶液中，FSW 表现出比 BM 更好的耐腐蚀性。