Microstructural development and aging behavior of Al-Cr-Zr heat-resistant alloy fabricated using laser powder bed fusion

Using laser powder bed fusion (L-PBF), we designed and fabricated specimens of a heat-resistant Al-4mass%Cr-1.5mass%Zr alloy (Al-4Cr-1.5Zr). The Al-4Cr-1.5Zr L-PBF specimen achieved high relative density greater than 99.9% by optimizing the laser scan conditions. The hardness and tensile and 0.2% proof stresses of the Al-4Cr-1.5Zr L-PBF specimens significantly increased after aging heat treatments, and the peak-aged specimens exhibited excellent high-temperature strength. The L-PBF specimens consisted of coarse columnar and fine equiaxed crystal grains owing to heterogeneous nucleation by the primarily crystallized Al3Zr phase. In the peak-aged L-PBF specimen, a finely dispersed Al3Zr granular phase on the order of single nanometers was precipitated in the alpha-Al matrix by aging. Meanwhile, the chromium was supersaturated in an alpha-Al solid solution even after peak aging, and partially precipitated into coarse granular Al-Cr-based compounds. These multi-scale microstructural observation results revealed that the dominant strengthening factors in the Al-4Cr-1.5Zr L-PBF specimens were precipitation hardening by the fine L1(2)-Al3Zr phase having a strong crystallographic consistency with the alpha-Al matrix, solid-solution hardening with chromium, dispersion hardening due to the Al-Cr-based compounds, and hardening by the crystal grain refinement mainly with the fine equiaxed grains. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

In this study, specimens of a heat-resistant Al-4Cr-1.5Zr alloy were designed and fabricated using laser powder bed fusion. By optimizing the laser scan conditions, the specimens achieved high relative density and exhibited significantly improved mechanical properties after aging heat treatments, showing excellent high-temperature strength.