Role of shielding gas and rolling treatment on mechanical properties of CP-Ti sheet fabricated by selective laser melting

Commercially pure titanium (CP–Ti) took advantages of low stiffness, high corrosion resistance and bio-compatibility, implying an ideal structural material in aerospace, military and medical industries. However, its insufficient mechanical properties have always been the long-standing obstacle for the industrial applications. In this work, we have achieved a superior strong and ductile CP-Ti via active atmosphere-assisted selective laser melting (SLM) and subsequent rolling treatment. By incorporating the active N2 atmosphere during SLM, mechanical properties of CP-Ti were substantially improved, microhardness of the lyaers with 10 at.% and 100 at.% was 63 % and 174.3 % higher than that of CP-Ti with 182.3 HV0.2, the compressive strength of 10 sample was 27.1 % higher than that of 10 L sample when the strain was 52.2 %, and ultimate tensile strength of 10 sample reached 928 MPa with an elongation of 25.6 %, and ultimate tensile strength and elongation of 10 L sample were enhanced simultaneously by 58.3 % and 13.6 % relative to CP-Ti sample. These were attributed to the interstitial strengthening induced by N atoms. After rolling treatment, the mechanical properties of N-doping layers could enhance furtherly. Macroscale cracking along the rolling direction never occur in the 10 L sample during the repeatedly rolling treatment, which could depend to high tolerability of sandwich layers for high-density dislocations. Meanwhile, rolling treatment played an important role for refining grain to enhance the strength further.