Hot working and microstructural response of ultrasonically fabricated 2 wt%ZrB2/AA7068 composite

Abstract

Hot compression is an efficient and widely accepted route for optimizing the microstructural characteristics of metallic materials; thus, understanding hot deformation response is essential for producing the upgraded material. The present research investigated the hot working behaviour of ultrasonically fabricated in-situ 2 wt%ZrB2/AA7068 composite to obtain a dendrite-free microstructure after single-step compression. Compression response is studied in the broad thermomechanical range of T = 250–450 °C and ε̇=0.001-1 s−1. The true stress-true strain of the deformed specimens increases with an increase in the deformation rate and a decrease in temperature. The constitutive equation was established, which precisely predicted the flow behaviour of the material. A 3-dimensional workability map was plotted to study the workability with increasing strain. The workability map has displayed the highest power dissipation efficiency of 39 % in the domain of 433–450 °C, 0.04–0.01 s−1. Hot forging simulation through DEFORM-3D indicated a higher effective strain in the centre of the deformed specimens. EBSD IPF and GOS micrograph illustrated strained microstructure at lower temperatures ≤ 375 °C, ≤ 0.1 s−1, whereas fair recrystallization was observed at 375 °C, 0.001 ≤ ε̇≤ 0.01 s−1. The dynamic softening indicated the occurrence of DRV and CDRX. Additionally, the occurrence of PSN was also observed in the deformed microstructure. After hot working, the best-working region for a dendritic-free microstructure is recognized in 380–450 °C, 0.001–0.5 s−1. Microstructural evolution and workability map were in line with each other.