Abstract:

Reactive spark plasma sintering (RSPS) provides a route to toughen boron carbide (B₄C) for lightweight armor applications by forming a ductile intermetallic binder in situ without promoting deleterious ceramic–metal reaction products. This paper investigates B₄C–NiAl “rebinder” cermets processed by RSPS, in which elemental Ni and Al react exothermically during the early stage of the SPS cycle to synthesize NiAl (observed at approximately 505 °C in the presence of B₄C), followed by high-temperature consolidation to near-full density. Cermets containing ~10 vol% NiAl are fabricated to quantify the composition–processing–microstructure–property relationships and to identify an optimal binder fraction that maximizes specific fracture toughness while preserving the intrinsic hardness advantage of B₄C. Microstructures and phase distributions are characterized by SEM (including compositional contrast and EDS mapping) to evaluate NiAl connectivity, porosity, grain-boundary wetting, and interface integrity, and XRD is used to confirm phase constitution and verify the absence of unintended reaction products. Mechanical response is assessed via Vickers hardness and indentation fracture toughness, supported by density measurements for specific-property comparisons. Preliminary proof-of-concept RSPS trials have already demonstrated a dense B₄C–NiAl microstructure with a chemically clean interface, along with hardness of 28.3 ± 0.7 GPa (HV1) and indentation fracture toughness in the range 3.5–6.4 MPa·m^1/2 (average ≈ 5.0 MPa·m^1/2) at an effective NiAl content of 11.3 vol%, indicating substantial toughening with minimal hardness penalty.

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Mr. Richard Holloway