Alloy Design and Microstructure Evolution in the AlxCoCrFeNi Alloy System Synthesized by Laser Metal Deposition

Abstract

In this contribution the Al x CoCrFeNi alloy system is explored thoroughly over a wide compositional range of x = 0.2 to 1.5 (5 to 30 at% Al). For this alloy system compositional gradient structures were produced by laser metal deposition of pre-alloyed CoCrFeNi and elemental Al powders using an in-house developed coaxial cladding system COAXpowerline. The evolution of the microstructure with increasing Al content was analyzed in the as built as well as the homogenized condition (1350 K for 20 h). Metallographic cross sections were prepared and thoroughly analyzed by means of scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron backscattered diffraction. Additionally, the evolution of the sample hardness with increasing Al contents was determined for both sample conditions. In the Al x CoCrFeNi alloy system the lattice structure as well as the sample hardness can easily be adjusted by the variation of Al. With increasing Al content a phase transition from a solid solution fcc phase toward a multiphase bcc microstructure consisting of a Fe and Cr rich solid solution bcc phase and an ordered Al and Ni rich bcc B2 phase can be observed. This is combined with an increase in sample hardness from around 200 HV up to around 500 HV in the as built condition. The compositional regions of the phase transitions for both sample conditions were compared to ab initio thermodynamic calculations done using a CALPHAD approach. For the as built condition a strong deviation from the calculated transition regime could be observed. After homogenization the experimental and calculated data are in good agreement.

Experimental Methods to Enable High-Throughput Characterization of New Structural Materials

“…15 Recently, laser metal deposition processes with a dynamic blending of powder have been developed to synthesize graded high-throughput samples. 7,17,18 Since the process is highly scalable, samples sizes can be easily varied to accord for characterization requirements. Such samples are well suited for accelerated evaluation of microstructures, occurring phases, and hardness measurements.…”

Multimaterial Additive Manufacturing of Graded Laves Phase Reinforced NiAlTa Structures by Means of Laser Metal Deposition

“…Moreover, Kuczyk et al applied this approach for conducting high throughput compositing screening for material development. [ 24 ] Hence, this approach shows high potential for investigating the influence of different alloy compositions on the processability and properties in a high throughput manner.…”