Improved tensile properties of selective laser melted GH4099 superalloy assisted by appreciable work hardening ability

Here, heat treatment-dependent microstructural evolution and tensile properties obtained by uniaxial tensile test and small punch test (SPT) of the selective laser melting (SLM)-fabricated GH4099 alloy are investigated. The columnar grains characterized by predominant Cube texture exponent in the as-SLM condition transform into random-oriented recrystallized grains with profuse twins after solution treatment. Upon aging, dispersed nano-sized coherent gamma' precipitates generate. Uuniaxial tensile test results indicate a balance of ultimate tensile strength (UTS) and uniform elongation in the aged sample, i.e., -1206 MPa and - 21% vs. -948 MPa and 27% in the as-SLM sample. The present study highlights the predominant role of dispersed coherent gamma' precipitates on the appreciable work hardening ability and hence better tensile property. The analysis of work hardening rate curves indicates the dislocation accumulation rate is comparable between the aged sample and the solution-treated sample, both of which are higher than that in the as-SLM counterpart. Appreciably, lower dynamic recovery rate exists in the aged alloy due to strong gamma' particle-dislocation interactions, which favors higher work hardening rate among the three conditions. Nevertheless, the strong S, Rotated-Copper and RotatedGoss components originating from preferential grain growth allow for uniform elongation decreased in the aged sample. Meanwhile, unified correlation equations between SPT and uniaxial tensile test are established for the present GH4099 alloy, which aims at providing an empirical relationship to evaluate tensile properties of the SLM-fabricated GH4099 alloy undergone various post-heat treatment.