Microstructures and corrosion resistance properties of as-cast and homogenized AlFeNiCuCr high entropy alloy
MATERIALS CHEMISTRY AND PHYSICS
Authors: Wang, Xin; Zhang, Yunpeng
The microstructure and corrosion resistance properties of as-cast and homogenized AlFeNiCuCr high entropy alloy prepared via magnetic suspension melting were investigated by XRD, DSC, SEM, EDS and electrochemical impedance spectroscopy test. The as-cast AlFeNiCuCr HEA was composed of grey white matrix, petal-shaped structure and Cu enrichment phase. This three different phases were identified as the ordered B2, disordered BCC and FCC phase, respectively. For the homogenized alloy, the diffraction peaks of Al0.4Fe0.6 was detected, indicating that new phases have been precipitated from the BCC matrix. In comparison to the as-cast alloy, the atomic percentage of Cu content increases from 50.69 to 57.17 at. % at grain boundaries illustrate that homogenization treatment intensifies the element segregation in the copper segregation area. The as-cast alloy exhibits super Vickers hardness of 762 HV which is higher than that reported by others. Following homogenization, the fracture strength increases from 1643 to 1799 MPa. The electrochemical parameters of AlFeNiCuCr system in 3.5 wt% NaCl solution at room temperature demonstrate that the as-cast alloy possesses the best corrosion resistance.
Structure and mechanical properties of a low-density AlCrFeTi medium entropy alloy produced by spark plasma sintering
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Authors: Shaysultanov, D.; Nepapushev, A.; Zherebtsov, S.; Moskovskikh, D.; Stepanov, N.
Bulk equiatomic AlCrFeTi medium entropy alloy was produced by mechanical alloying (MA) and spark plasma sintering (SPS). Powders with a homogeneous chemical composition composed of amorphous and bcc phases were obtained due to MA. Bulk, almost porosity free specimen of the alloy with the measured density of 5.53 +/- 0.07 g x cm(-3) was obtained after SPS. A mixture of a (Fe, Ti)-rich C14 Laves phase, a Cr-rich bcc phase, and an Al-rich L1(2) phase was found in the as-sintered specimens. The average size of grains/particles of the different phases was 115 +/- 100 nm. Annealing at 1000 degrees C resulted in some coarsening of the microstructure to the grain/particle size of 140 +/- 120 nm and in an increase in the fraction of the bcc and L1(2) phases, yet the microstructure was found to be relatively stable. After SPS the AlCrFeTi alloy had a high microhardness of 1090 +/- 120 HV, which decreased after annealing to 870 +/- 70 HV. Compression tests have meanwhile revealed low ductility of the alloy after SPS - the alloy exhibited brittle fracture at room temperature and became ductile at only 800 degrees C. After annealing the alloy demonstrated reasonable ductility already at 700 degrees C. Also, the annealed alloy had a remarkable specific yield strength of 258 kPa x m(3)/kg at 700 degrees C. The experimental data on the phase composition of the alloy was compared with the Thermo-Calc predictions, and the relationships between the structure and properties of the alloy were discussed.