A review of multi-physical fields induced phenomena and effects in spark plasma sintering: Fundamentals and applications

Powder metallurgy of Al0.1CoCrFeNi high-entropy alloy

“…Eventhough the single fcc phase was reported by other researchers [9,10,11,12,13,14], in Al 0.1 CoCrFeNi HEA prepared by arc melting and induction melting techniques, Al 0.1 CoCrFeNi HEA prepared by MA shows the two-phased crystal structure. Such occurrence also observed during MA of CoCrFeMnNi HEA (which possesses a single fcc phase when prepared by arc melting and induction melting techniques) [61,64].…”

“…However, with increasing the MA time, the identity of the individual elemental phases disappears, and the peaks corresponding to two crystal structures fcc and bcc are observed. The width of the peaks increases with increasing MA time, and this broadening may be attributed to the following factors: (i) decrease in the crystallite size or the coherent domain size, (ii) increase in the lattice strain or internal strain in the material, and (iii) increase in the number of internal defects like the dislocation density and stacking faults [64]. Besides, the peaks corresponding tend to shift toward a lower angle due to the alloying of the elements, eventually forming an alloy with high entropy in it.…”

“…It can be noted that the increase in the lattice parameter during MA is less compared with that of SPSed A-HEA. This is attributed to the pronounced phase transition in SPS consolidation than during MA due to the assistance of the thermal energy [64]. The crystallite size of the bulk HEA sample is ∼48 nm, and the lattice strain is evaluated as 2 × 10 −3 (no unit).…”

Refractory High-Entropy HfTaTiNbZr-Based Alloys by Combined Use of Ball Milling and Spark Plasma Sintering: Effect of Milling Intensity

“…For consolidation of HEAs powders, conventional sintering methods are often used, which include vacuum hot pressing sintering, microwave sintering, and hot isostatic pressing. Among these, a highly promising technique for sintering and production of HEA materials is spark plasma sintering (SPS) [32][33][34]. The main difference between SPS and conventional hot pressing is that, in SPS, the current is applied as many pulses over very short times (less than milliseconds (ms)) instead of one single pulse for a long time.…”

“…As with most methods where pressure and temperature are applied simultaneously, both pressure and temperature are lower than would be required if applying them in subsequent steps. This means that lower sintering temperatures and shorter holding times are required, and as a result, less grain growth and better properties can be obtained [33,35].…”