Page 24 - Annual Report_21-22

ADVANCED MATERIALS TECHNOLOGY

Development of novel tungsten heavy alloy using high entropy alloy as binder

Tungsten Heavy Alloys (WHAs) consisting of 88-98 wt.% of of sintered WEMs (W-EleMental: powder mix of W and
W and 12-2 wt.% of based binder, processed by powder elements of Fe, Ni, Co, Cr, and Cu in equiatomic ratio). In
metallurgy route, has been emerged as the material of addition, the effect of hydrogen treatment (HyT) in WHEAs
choice for application in various strategic sectors due to before compaction on microstructure and mechanical
their unique properties such as high density, high strength, properties are shown. XRD patterns of sintered samples
high impact strength and corrosion resistance, etc. showed peaks characteristic to W and austenitic matrix
Recently, High Entropy Alloys (HEAs) have been used as a g-phase (Fig. 1). Also, peaks of Cr-oxide and s-phase are
filler/reinforcement in various metal matrix composites to seen. The sintered microstructures showed typical liquid
improve their mechanical properties. phase sintered morphology, consisted of bright W-grains,
gray matrix phase, and black Cr-Oxide phase (Fig. 2). The
In the present work, FeNiCoCrCu HEA is utilized as binder Cr metal separates out from the matrix and gets oxidized
replacing the traditional Ni-based binder to fabricate to form Cr-oxide (Cr has a higher affinity for oxygen to form
WHAs, processed through the conventional sintering oxides compared to other dissolved elements). During
technique. 90 wt.% W and 10 wt.% HEA powders are Bulk hardness and compression measurements of these
mixed, compacted, and sintered at two temperatures alloys (WHEAs and WEMs) showed higher values in case
of 1470 and 1500°C in H atmosphere. These alloys are of WHEAs compared to WEMs (Fig. 3). The introduction
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denoted as WHEA. The evolution of microstructure and of HyT in W+HEA powder resulted in higher strength
mechanical properties of WHEAs are compared with those compared to WHEAs upon sintering (Fig. 3).

Fig. 1: XRD patterns of (a) WEM-1470, (b) WEM-1500, (c) WHEA-1470, (d) WHEA-
HyT-1470, (e) WHEA-1500, and (f) WHEA-HyT-1500.

Fig. 2: FESEM images of (a) WEM-1470, (b) WHEA-1470, (c) WHEA-HyT-1470, (d) WEM-
1500, (e) WHEA-1500 and (f) WHEA-HyT-1500.

22 ANNUAL REPORT 2021-22