Morphology evolution of prior β grains of laser solid forming （LSF） Ti-xAl-yV （x 11,y 20） alloys from blended elemental powders is investigated. The formation mechanism of grain morphology is revealed by incorporating columnar to equiaxed transition （CET） mechanism during solidification. The morphology of prior β grains of LSF Ti-6Al-yV changes from columnar to equiaxed grains with increasing element V content from 4 to 20 wt.-%. This agrees well with CET theoretical prediction. Likewise, the grain morphology of LSF Ti-xAl-2V from blended elemental powders changes from large columnar to small equiaxed with increasing Al content from 2 to 11 wt.-%. The macro-morphologies of LSF Ti-8Al-2V and Ti-11Al-2V from blended elemental powders do not agree with CET predictions. This is caused by the increased disturbance effects of mixing enthalpy with increasing Al content, generated in the alloying process of Ti, Al, and V in the molten pool.
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
