Composite rods by high-temperature gas extrusion of steel cartridges stuffed with reactive Ni–Al powder compacts: Influence of process parameters

Abstract

Steel clad NiAl rods were prepared by high-temperature gas extrusion (HTGE) of steel cartridges stuffed with reactive Ni–Al powder compacts upon variation in warmup temperature Tw (600–780 °C) and gas (Ar) pressure P (200–480 MPa). A largest amount of NiAl and Ni3Al intermetallics in rod core was obtained at Tw = 780°С and P = 200 MPa. For Tw < 660°С (m.p. of Al), the rod core was found to contain significant amounts of unreacted Al and Ni. A transition zone of Al–Fe intermetallics (10 μm thick) was found only in the rod obtained at Tw = 780°С and P = 200 MPa. The core material of such rods exhibited a largest mean value of hardness (1050 HV). It is suggested that the yield of target intermetallics can be improved by using charge compacts prepared from mechanically activated Ni–Al blends. Combined use of (a) in-situ synthesis of target product in a core and (b) extrusion of the entire fixture seem promising for fabrication of composite materials with unique properties.