Tungsten heavy alloys are unique composites consisting of tungsten grains in a matrix, produced only by powder metallurgy technique. This study aimed to investigate the effect of adding Cr element on the microstructure and mechanical properties of W-Ni-Fe tungsten heavy alloys, therefore two WHA and WHA-Cr alloys were designed and manufactured using the same liquid phase sintering process. The microstructural results showed that in the WHA sample, only α σ‑tungsten grains and γ-matrix phase were present, whereas in the WHA-Cr alloy, the chromium-rich sigma ( ) phase was also formed along with the α- and γ-phases. Furthermore, thermodynamic studies using JMatPro software showed that the potential formation of the sigma phase and decline in the liquid phase led to the retardation of sintering phenomena in the WHA-Cr alloy. The addition of chromium had undesirable effects, such as increased porosity, decreased density (17.31 g/cm 3 in WHA and 16.38 g/cm 3 in WHA- Cr), and increased contiguity number of W-W interfaces (from 0.21 in WHA to 0.47 in WHA-Cr). Moreover, the results showed that the hardness of the WHA was (30 HRC) lower than that of WHA-Cr (48 HRC); whereas the tensile properties of WHA (YS = 674 MPa, UTS = 942 MPa, El% = 14.5) were better than those of the WHA-Cr alloy (YS = 423 MPa, UTS = 502 MPa, El% = 3.8). These properties were attributed to the addition of chromium by two factors: (1) the formation of σ-phase, a very hard phase with an 850 HV. value, and (2) a high contiguity number, which was briefly discussed. Finally, it should be noted that although WHA-Cr alloys are undesirable for conventional applications owing to their lower overall properties, their production with least defect and high density can be suitable for some special applications with higher hardness such as wear and erosion conditions.

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