The heterogeneous nucleation behaviors of NH4Cl crystal on rough aluminum substrate surface immerged in NH4Cl-H2O solution were experimentally analyzed, and the influence mechanism of the micro/nano-scale surface structures on heterogeneous nucleation was investigated. It has been shown that wettability and nucleation are affected by substrate surface condition. The intrinsic wetting properties between nucleus and substrate surface, and the surface structure of certain geometrical scales, both impose effects on the heterogeneous nucleation properties. For a nucleus-wetting substrate surface, heterogeneous nucleation is promoted by a higher complexity of the surface morphology; but for a nucleus-nonwetting substrate surface, heterogeneous nucleation is inhibited by a higher complexity of the surface morphology.
Laser solid forming (LSF) is an advanced manufacture technology developed from early 1990s, which can realize the rapid manufacturing high performance near-net-shaping complicated metallic components with full-dense directly. Currently this technology has been widely used for rapid manufacturing of metal parts, repairing and remanufacturing service of large parts with defects in aerospace, energy, transportation industry etc. In present paper, the main progresses on the research and application of LSF are reviewed, and the emphasis has been focused on manufacturing high performance high strength steel metal parts. The results of LSFed high strength steel samples show that the comprehensive mechanical properties are usually in the classes of forging parts, which the dense, fine and homogeneous microstructure in LSFed parts, especially, high strength steel parts with metallurgical-defects-free can be obtained by careful optimizing the forming and heat treatment parameter. To realize the high performance repairing and remanufacturing of the high strength steel component is one of the most remarkable progress for LSF recently. The mechanical properties of the repaired and remanufacturing parts by LSF can reach the wrought standards only with annealing treatment. It is believed that the repair and remanufacturing of high performance metallic components by LSF should be one of the most promising applications for LSF in the coming future.
Yang Haiou, Lin Xin, Wu Xiaoyu, Huang Chunping, Huang Weidong The State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
