Surface nanocrystallization of Cu-Cr alloy by a high power density continuous laser beam

摘要： A nanostructured surface layer of (cid:1)300 lm thickness was fabricated on Cu-30Cr (wt%) hypereutectic alloy by a continuous laser beam with high power density (1.08 (cid:3) 107 W/cm2). The average grain size of Cr-rich particles was re?ned to (cid:1)40 nm, and the solid solubility limit of Cr in Cu was extended to 1.96 at. %. Experimental results show that the dispersion of nano-sized Cr-rich spheroids in Cu-rich matrix was attributed to the Brownian motion of Cr-rich spheroids, and the high cooling rate (5.75 (cid:3) 106 K/s) during liquid phase separation which inhibits the collisions between Cr-rich spheroids.