Improvement in the high-temperature creep properties via heat treatment of Ti-6Al-4V alloy manufactured by selective laser melting

초록

This study seeks to control the microstructure of Ti-6Al-4V alloy produced by a selective laser melting process using only heat treatment, while also improving the high temperature creep behavior. Initial microstructure observation showed a fully martensite structure for the as-fabricated specimen and a fine widmanstatten structure for the heat-treated specimen. Hardness tests indicated that the hardness of the material decreased somewhat, but the anisotropy of the mechanical properties (common in additive manufactured materials) disappeared. Compression tests at 500 degrees C indicated that the yield strength of the as-fabricated specimen was approximately 930 MPa, while in the heat-treated specimen it was approximately 557 MPa. High temperature compressive creep tests showed that the heat-treated specimen had relatively low creep strain and low steady-state creep rate (superior creep resistance) in all stress ranges, which is the opposite of the compressive yield strength results. After creep deformation, the microstructural evolution of the as-fabricated and heat-treated specimens was compared, and the microstructure changed much more extensively in the as-fabricated specimen. Correlations between microstructures, hardness, strength and creep properties were discussed based on these results.

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