Engineering heterogeneous microstructures in additively manufactured high entropy alloys for high strength and strain hardenability

Feasibility Studies and Downselection of New Materials and Manufacturing Technologies for Nuclear Applications

“…Additionally, some grains also exhibit solidification cells presumably arising from compositional segregation owing to the high solidification rates involved in DED processing. However, the possible formation of early-stage nanoscale L12 precipitates within the fcc matrix of the DED(AD) condition was previously observed in high-energy synchrotron x-ray diffraction results [185]. The annealing heat treatment (800°C for 5 h) conducted on the DED-processed HEA led to the partial recrystallization of fcc grains and a significant growth of the non-recrystallized fcc grains.…”

“…This HEA was fabricated via two different AM techniques: DED and SLM. The evolution of the heterogeneous microstructures in the AD and subsequently annealed conditions and their tensile properties at RT have been reported previously [68,185]. However, the temperature-dependent mechanical behavior essential for nuclear applications was not yet investigated.…”

“…Considering this process, AM methods such as DED [42,59,60,61] can be beneficial because materials with significantly better properties than the conventionally cast counterparts can be obtained [62,63,64,65,66]. Moreover, straightforward, one-step annealing approaches can be designed by exploiting the residual stresses in these AM techniques to successfully engineer microstructures with multiple interfaces desired for nuclear applications [67,68]. The DED process can also enable the fabrication of functionally graded materials that possess applications across different industries, including nuclear.…”

“…Directed Energy Deposition: Laser engineered net shaping (LENS [63,67]), wire arc AM (WAAM) [80][81][82][83], and electron beam AM (EBAM) are the most popular DED techniques used for processing HEAs. LENS is a powder-fed technique, and WAAM and EBAM are wire-fed techniques.…”

Post-processing treatments–microstructure–performance interrelationship of metal additive manufactured aerospace alloys: A review

“…The as-built LENS-processed Al0.3Ti0.2Co0.7CrFe-Ni1.7 high entropy alloy was subjected to post-processing heat treatments [157]. A balance of mechanical properties was attained after the single-step annealing treatments (at 600°C for 50 h and 800°C for 5 h) of the HEA due to the induced hierarchical heterogeneous microstructure (γ, γ′, and σ phases) [157]. The as-built MAM-produced FeCrCoMnNi equiatomic HEA alloy was revealed to possess a single FCC phase with a dendritic columnar and equiaxed grain structure [158].…”