The solidification and phase transition behavior during printing process of Ti-5Al-5Mo-5V-3Cr-1Zr ( Ti-55531 ) alloy made by selective electron beam melting ( EBM ) technology was investigated. Firstly,coarse columnar grains formed in the direction of construction of sample,the low nucleation barrier at the solidification front of the melt pool during EBM leads the critical nucleation radius of the grain r∗ to tend to 0,the equiaxed grains cannot be generated. At the same time,the solidification mode changes from planar solidification to dendrite solidification,and the low equiaxed dendrite ratio makes it impossible to transform from columnar to equiaxed grain. Under the influence of the remelting zone and directional heat flow,the grains grow into cross-layered columnar crystals along the construction direction,and the microstructure of the samples shows a gradient structure along the construction direction. With the increase of deposition height,the proportion of primary αp in the sheet decreases,the width increases,and the proportion of secondary αs increases,which is the result of the combined effect of heat accumulation along the construction direction and in-situ heat treatment of substrate heating.
关键词
电子束选区熔化/Ti55531合金/凝固行为/相变
Key words
selective electron beam melting/Ti-55531 alloy/solidification behavior/phase transition
维普
万方数据