Enhanced compressive strength and tailored microstructure of selective laser melted Ti-46.5Al-2.5Cr-2Nb-0.5Y alloy with different boron addition

The microstructures and compressive properties of Ti-46.5Al-2.5Cr-2Nb-0.5Y alloy with varied boron (B) addition processed by selective laser melting (SLM) had been systematic studied. With increasing the B content from 0 to 2 wt%, the average grain size of SLM-processed Ti-46.5Al-2.5Cr-2Nb-0.5Y/B composites decreased from 16.64 mu m to 5.66 mu m, meanwhile, the {0001} texture index and high angle grain boundaries (HAGBs) increased from 10.78 and 87.9% to 22.69 and 94.4%. The phase evolution mechanism of Ti-46.5Al-2.5Cr-2Nb- 0.5Y/B composites during the SLM process can be summarized as: firstly, beta and B phases precipitated out from the liquid phase, then the beta phase transformed to alpha phase and part of the a phase transferred to gamma phase, later, some new phases of TiB2 and AIB(2) emerged by the diffusion mechanism of B, Ti and Al atoms, and then the beta and a phases orderly transformed to B z and alpha(2) , lastly, the gamma, B-2, B, TiB2 , AlB2 phases in a range of several hundred nanometers were randomly distributed within the alpha(2) matrix. Due to the grain refinement strengthening mechanism, the compressive strength and strain of Ti-46.5Al-2.5Cr-2Nb-0.5Y/13 parts increased to the maximum of 1610.53 MPa and 5.17%.