Enhanced Strength of a Mechanical Alloyed NbMoTaWVTi Refractory High Entropy Alloy

Abstract

A NbMoTaWVTi refractory high entropy alloy (HEA) has been successfully synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and mechanical properties of this alloy are investigated. It is observed that only two types of body-centered cubic (BCC) solid solutions are formed in the powders after ball milling for 40 h. However, a new face-centered cubic (FCC) precipitated phase is observed in the BCC matrix of bulk material consolidated by SPS. The FCC precipitated phase is identified as TiO, due to the introduction of O during the preparing process of HEA. The compressive yield strength, fracture strength, and total fracture strain of the consolidated bulk HEA are 2709 MPa, 3115 MPa, and 11.4%, respectively. The excellent mechanical properties can be attributed to solid solution strengthening and grain boundary strengthening of the fine-grained BCC matrix, as well as the precipitation strengthening owing to the formation of TiO particles.

Structure and Phase Composition of a W-Ta-Mo-Nb-V-Cr-Zr-Ti Alloy Obtained by Ball Milling and Spark Plasma Sintering

“…A common feature of the phase evolution process of multicomponent alloys obtained by solid-state processing is the formation of a "matrix" phase, which is a disordered substitutional solid solution of BCC structure, at the mixing and alloying stage (during ball milling) [20,21,[23][24][25]27,28]. In this work, the use of a high-energy ball mill dramatically reduced the milling time as compared with other studies.…”

“…In this work, the use of a high-energy ball mill dramatically reduced the milling time as compared with other studies. Indeed, the ball milling time can be several hours [23,25,27,28] or several tens of hours [20,21,24,25,27,28] depending on the type of milling equipment used (Table 4). [27] In addition to mixing, treatment in high-energy ball mills results in severe deformation of the materials and the formation of highly defect nanostructured states [39,40].…”

“…The microhardness of the alloy synthesized in the present work is comparable to that of alloys synthesized by other researchers ( Table 4). The strength of these alloys depends on a number of factors, which include grain refining [21,23,24,27], the fraction of Laves phase [21,23,25,28], the presence of reinforcing particles of other phases [20,21,24,25,27,28], and solid-solution strengthening [20,27,28].…”

“…The interest in these alloys is due to unique combinations of mechanical properties that they can offer when properly designed. Research in this area is aimed at finding new promising compositions [1][2][3][6][7][8][9], characterizing the microstructure and mechanical properties [10][11][12][13][14][15][16], studying the mechanisms of plastic deformation [4,17], or determining the phase composition and phase stability of the alloys [18][19][20][21][22][23][24][25][26][27][28][29].…”

“…In contrast to cast alloys, the SPS processing excludes the formation of dendrite structures. Attempts to produce multicomponent refractory metal alloys have been described in [20][21][22][23][24][25]27,28].…”