Effect of sintering temperature on microstructure and properties of tungsten heavy alloys using NiFeCoCr high entropy alloy as binder
NiFeCoCr high entropy alloy(HEA)with non-equal atomic ratio was adopted as a new bonding phase of tungsten heavy alloys.90W-NiFeCoCr alloy was prepared by spark plasma sintering.The effects of sintering temperature on the microstructure and mechanical properties of the alloy were investigated by scanning electron microscopy(SEM),energy microanalyzer spectrum(EDS),X-ray diffractometer(XRD),electron probe microanalyzer(EPMA),transmission electron microscope(TEM)and mechanical experiments.The results show that in the microstructure of the alloy,the HEA binder phase is formed,which is the γ(Ni-Fe-Co-Cr,W)phase with face-centered cubic(FCC)structure,and the Cr2O3 phase with close-packed hexagonal(HCP)structure appears.The relative density of the alloy increases first and then decreases with the increase of temperature.After sintering at 1 250℃,the relative density reaches the highest of 98％,the W grain size is fine(≤10 μm),the tensile strength reaches a maximum of 1 409 MPa,and the fracture morphology is mainly W-W dissociation fracture.The solid solution strengthening of HEA,the fine grain strengthening of W and the dispersion strengthening of the segregated phase Cr2O3 are the main reasons for the higher strength.
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