Effect of pre-milling (Ni and Al) on the sintering behavior of NiAlFeCoCr high entropy alloy

[Display omitted] •The effect of pre-milling Ni and Al powders on the sintering behavior of NiAlFeCoCr HEA is investigated.•Liquid phase sintering with the formation of viscous phase is evident in as-milled NiAlFeCoCr HEA (Q = 164 kJ/mol).•Solid-state sintering is observed in pre-milled (NiAl)FeCoCr HEA (Q = 198 kJ/mol).•The hardness of pre-milled (NiAl)FeCoCr HEA is greater than as-milled NiAlFeCoCr HEA. The present study aims at investigating the effect of pre-milling nickel (Ni) and aluminium (Al) powders on the sintering behaviour of NiAlFeCoCr high entropy alloys (HEA). As-milled NiAlFeCoCr HEA was prepared by mixing the Ni, Al, Fe, Co and Cr powders (in equiatomic ratio) for 10 h in a planetary ball mill. In case of pre-milled (NiAl)FeCoCr HEA, Ni and Al powders were initially milled for 5 h and this mixture was then further milled with Fe, Co and Cr powders for another 10 h. XRD, SEM-EDS, TG-DSC and Dilatometric analysis were performed for the characterization of these HEAs. The formation of FCC and BCC phases was observed in both, as-milled and pre-milled HEAs. The sintering behaviour (at 1000–1200 °C) of the HEAs was compared and observed that as-milled HEA sintered by viscous flow mechanism, which was absent in case of pre-milled HEA. An exothermic reaction observed in the as-milled HEA at 518 °C representing Ni and Al reaction, was absent in the pre-milled HEA, indicating that Ni and Al had reacted during the pre-milling process. The micro-Vickers hardness of as-milled HEA also increased from 638 ± 8.73 HV to 662 ± 12.24 HV upon pre-milling.