工艺参数对激光选区熔化Ti-22Al-25Nb合金成形质量及组织演化的影响OA

On the basis of the aerospace industry's demand for lightweight and high-strength Ti2AlNb-based alloys,a Ti-22Al-25Nb alloy was fabricated using selective laser melting(SLM)technology.The effects of laser power,scanning speed,and volumetric energy density(VED)on the forming quality,microstructure,and microhardness of the as-printed alloy were systematically investigated.The results show that the forming quality of the alloy is significantly controlled by the volumetric energy density.When the VED ranges from 38.89 to 138.89 J/mm3,the melt pool exhibits good stability and maximum density;however,both excessively low VED(＜31.75 J/mm3)and excessively high VED(＞250 J/mm3)induce a lack of fusion defects and keyhole porosity,respectively.The as-printed alloy exhibits a typical columnar grain structure with epitaxial growth along the build direction.High energy density promotes grain coarsening and results in the formation of a pronounced<001>fibrous texture,whereas the extremely rapid cooling rate at low energy density suppresses grain growth,resulting in fine,fragmented columnar grains with a random orientation.Finally,microhardness measurements of the alloys produced under different process parameters reveal a hardness distribution ranging from 242 to 267 HV.The hardness evolution is jointly influenced by density and grain size;fine-grained strengthening at medium-low energy density effectively compensates for the performance loss caused by porosity,whereas grain coarsening under excessive heat input leads to a decrease in hardness.