Synchronously Enhanced strength-ductility of L-DEDed GH4169 with Varying Energy Input

Abstract

The energy input highly determines the microstructure, texture and tensile properties of the laser directed energy deposited (L-DEDed) Ni-based superalloy. This study adopted three levels of energy input from low, medium to high evaluated by the areal energy density to fabricate GH4169 alloy. Results show that a synchronously enhanced strength-ductility of L-DEDed GH4169 Ni-based superalloy with the the high energy input, although the microstructure exhibits the largest grain size and most significant Laves phase size and fraction. This synchronously enhance strength-ductility of L-DEDed GH4169 with high energy input can be mainly attributed to the combined effect of texture variation and residual stress. The crystallographic characterization depicted a texture variation from the {001} <100> cube texture with low energy input to the {111} <110> Goss texture with high energy input, which can be quantitatively analyzed by the average Schmid factor for slip and twinning derived from the “Texture parameters (TP)”. In this case, the average Schmid factor for slip and twinning of the tensile specimen with high energy input are both the smallest, which enhances the yield strength and deformation twinning of the specimen. The microstructure observations showed that the texture variation of the L-DEDed samples from low to high energy input was dominated by the “maximum deviation angel θd” of dendrites determined by the melt-pool shape and related heat-dissipation direction. Besides, the residual stress decreases as the energy input increases, which also contributes to the enhanced strength-ductility with high energy input.