原料粉末对NiTi的选区激光熔化成形件性能的影响

Effects of raw powder on NiTi parts fabricated by selective laser melting

分别以Ni+Ti元素混合粉末和NiTi预合金粉末为原料,采用选区激光熔化工艺打印成形。重点研究了在相同打印工艺参数下原料粉末对成形件致密度、物相组成、显微组织、显微硬度的影响,从而反馈说明所用打印粉末对成形件性能的影响。结果表明:在相同打印工艺参数下,整体上NiTi预合金粉末成形件的致密度较高,而Ni+Ti混合粉末成形件的显微硬度较高。对于同一种粉末,随着能量密度的增大,成形件的致密度先增大后减小,而显微硬度先减小后增大。NiTi预合金粉末成形件有致密的微观结构且相分布均匀,但存在少量孔隙。Ni+Ti混合粉末成形件的微观结构有和构建方向垂直的贯穿式裂纹以及不均匀的基体相,但几乎没有孔隙。

In this study,Ni+Ti mixed powder and NiTi pre-alloyed powder were used to print by selective laser melting process.The effects of raw material powder on the density,phase composition,microstructure and microhardness of formed parts under the identical processing parameters are studied,so as to feedback the effects of raw powder on the properties of formed parts.The results showed that under the identical processing parameters,the density of the formed parts fabricated by NiTi pre-alloyed powder was higher,while the microhardness of Ni+Ti mixed powder formed parts was higher.For the same powder,with increase of energy density,density of the formed parts first increased and then decreased,while microhardness first decreased and then increased.NiTi pre-alloyed powder formed parts had dense microstructure and uniform phase distribution,but there presented several pores.The microstructure of Ni+Ti mixed powder formed parts has through cracks perpendicular to the construction direction and uneven matrix phase,but there are almost no pores in the structure.