Original Research PaperMorphology, 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
Introduction
The ball-milling method is widely used both for dispersing and mixing powders of metals and mixtures based on them, as well as a method for implementing intense deformation and low-temperature synthesis of compounds [1], [2], [3], [4], [5], [6], [7]. Today, ball-milling is widely used in the production of high entropy alloys based on refractory metals at the stage of creating precursors from multicomponent powder mixtures for subsequent spark plasma sintering (SPS) [8], [9], [10], [11], [12], [13], [14], [15], [16], [17]. This approach allows the synthesis of multicomponent compounds at lower temperatures, compared with the temperatures necessary for the melting of initial refractory components.
As is known, refractory metals-based alloys have traditionally been the basis for the creation of high-strength materials that are used in extreme conditions of high temperatures, high pressures, aggressive environments, etc. Among the most urgent tasks, one can single out a study of the features of the formation of structural-phase states and the corresponding level of physical and mechanical properties of such systems at different stages of treatment.
An analysis of the published data shows that a direction of current interest is related to the development of new compositions of multicomponent metal systems and the study of their structural-phase stability [9], [10], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25]. It was shown in [9], [10], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21] that during ball-milling of refractory powders mixtures the formation and transformation of main BCC phases is possible.
In this work, we studied the features of morphology, structural-phase state and microhardness of a multicomponent non-equiatomic mixture of W-Ta-Mo-Nb-Zr-Cr-Ti powders subject to the duration of ball-milling.
Section snippets
Materials and methods
A non-equiatomic mixture of refractory metal powders taken in equal weight proportions was used in the work. The resulting composition in weight (wt. %) and atomic (at. %) percents is shown in Table 1.
Ball milling of the powder mixture was conducted in a high-energy planetary ball mill AGO-2 with two water-cooled vials having a volume of 160 cm3 each. Stainless steel vials and balls were used. The diameter of the balls was 8 mm. The weight of the milling balls was 200 g, the weight of the
Results
Fig. 1 shows X-ray diffraction patterns of multicomponent powders mixture of the W-Ta-Mo-Nb-Zr-Cr-Ti system after 1, 3.5, 5.5, 7.5, 9.5, 11.5, 13.5, and 15.5 min of ball-milling.
The analysis showed that after ball-milling lasting 1 min, two main reflections at 2θ ≈ 38.5° and 40.3° are observed in the corresponding X-ray diffraction pattern, characterized by the maximum intensity with the corresponding half-width Δ(2θ) ≈ 0.42° and 0.51°. It was found that the reflection at 2θ ≈ 38.5° is the
Discussion
An analysis of the results obtained in the work shows that the transformation of the structural phase state and the change in the microhardness of the multicomponent W-Ta-Mo-Nb-Zr-Cr-Ti system are characterized by staging depending on the duration of ball-milling. Three main stages have been identified.
The first stage corresponds to the interval of ball-milling from 1 to 7.5 min. At this stage, the formation of large conglomerates is accompanied by mixing processes of the initial components. On
Conclusions
Three main stages of the structural-phase state transformation and microhardness changes of the multicomponent W-Ta-Mo-Nb-Zr-Cr-Ti system under high-energy ball milling conditions were revealed. Corresponding to different processing times, the stages differ in the morphology of the powder mixture, the distribution of components, phase compositions and the character of the change in microhardness.
It has been established that already at the initial stage of high-energy ball milling, two phases
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
The studies were carried out using the equipment of the Tomsk Materials Science Center for Collective Use of the National Research Tomsk State University.
Author Contributions
Conceptualization, I.A.D. and M.A.K.; data curation, I.A.D., I.V.S. and K.V.G.; scanning electron microscopy, I.V.S.; X-ray diffraction analysis, I.V.S.; microhardness, D.A.O.; mechanical activation, A.I.G.; Writing, I.A.D. and K.V.G.; Supervision, I.A.D.
Funding
Structural investigation and microhardness testing were performed according to the Government research assignment for ISPMS SB RAS, Project No. III.23.2.6. Ball milling was carried out with the state assignment to ISSCM SB RAS, project No. AAAA-A17-117030310277-6.
Data availability
The data are available on request.
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