Crystallographic features of α variants and β phase for Ti-6Al-4V alloy fabricated by selective laser melting

The present study investigated the crystallographic features of a variants and beta phase for Ti-6Al-4V alloy fabricated by selective laser melting. The <100>(beta) fiber texture parallel to the building direction was ascertained on the basis of a reconstruction method realized by the manipulation of stereographic projection. The SLMed alloy has no alpha/alpha' variants selection but contains a special crystallographic area exhibiting random orientation which cannot be reconstructed as a parental columnar beta grain with the present introduced method due to its nature as the overlapped area between adjacent melt pools resulting from the heterogeneous nucleation in front of the liquid-solid interface. With increasing the heat treated temperature, alpha variants selection occurs. Especially at higher temperature of 905 degrees C, the intergranular beta phase following a reversed crystallographic path as parental beta phase->alpha variants->intergranular beta phase would be precipitated, therefore the intergranular beta phase keeps the same orientation with the parental beta phase. Once the alloy was heat treated at 975 degrees C close to T-beta, the microstructure is characterized by primary alpha variants selection and a large amount of secondary a widmanstatten structure with a homogeneous orientation which accounts for the lowest tensile strength. The decomposition of twelve alpha variants proved the BOR <110>(beta)//(0001)(alpha), <111>(beta)//<2-1-10>(alpha). The misorientation between two variants sharing a common parental <100>(beta) pole with a similar color consisting of all Euler angles was identified to be [0001] (alpha)/10.53 degrees.