Morphology, structural-phase state and microhardness of a multicomponent non-equiatomic W-Ta-Mo-Nb-Zr-Cr-Ti powders mixture depending on the duration of ball milling

Structural-Phase State and Microhardness of a Precursor from Equiatomic W-Ta-Mo-Nb-Zr-Cr-Ti Powder Mixture after High-Energy Mechanical Activation

“…4). Similar features of the distribution of chemical elements were found in the nonequiatomic W-Ta-Mo-Nb-Zr-Cr-Ti system after mechanical activation for 9.5-15.5 min [11]. Such an increase in the Fe concentration during high-energy mechanical activation is associated with the contamination of the W-Ta-Mo-Nb-Zr-Cr-Ti powder mixture with the elements of the mill vials.…”

“…In our opinion, the revealed features result from an increase in the Fe concentration, which has a larger lattice parameter in comparison with Cr (Table 2). In the previous work on the nonequiatomic W-Ta-Mo-Nb-Zr-Cr-Ti system with a high Cr concentration (more than 23 at %) [11], it was found that chromium tends to dissolution at longer mechanical activation. In the presently studied system, the Cr concentration is significantly lower and amounts to 14.3 at % (Table 1).…”

“…In addition, the energy dispersive analysis reveals that the concentration of O and C in these regions is 15-20 at % higher as compared to the surroundings. It was previously shown for the nonequiatomic W-Ta-Mo-Nb-Zr-Cr-Ti system that such regions contain particles of oxide and carbide phases based on Zr, Cr, and Ti [11]. As is known [21], high reactivity of refractory materials with interstitial impurities is often the reason for precipitation of second-phase particles, which changes them into heterophase materials.…”

“…One of the urgent tasks of this scientific direction is to reveal how chemical composition and its equiatomicity affect the formation and transformation of the main phases during both mechanical activation of precursors and subsequent spark plasma sintering. By the example of various systems it was shown [4][5][6][7][8][9][10][11][12][13][14][15][16] that intensive dispersion and mixing of the initial components is accompanied by the formation of one or more phases directly during mechanical activation. In many systems of refractory metals, the resulting main phase has a bcc lattice.…”

“…In many systems of refractory metals, the resulting main phase has a bcc lattice. Mechanical activation of the nonequiatomic W-Ta-Mo-Nb-Zr-Cr-Ti system causes the formation of two bcc phases, one of which is a precursory state for Laves phases that can be found after spark plasma sintering [10,11].…”