Microstructures of some high tensile brasses

Abstract

The microstructures of extruded high tensile brasses with compositions conforming to BS 2872/4 CZ114, CZ115, and CZ116 consist of copper rich fcc α-phase, ordered B2 β′-phase, and some iron rich particles; these particles are α-Fe in alloy CZ115 and Fe₃Al in alloy CZ116. Alloy CZ114 contains mainly α-Fe particles, although a few, small precipitates of Fe₃Al have also been observed. It is shown in studies of the microstructural development that the α-Fe particles are formed in the liquid, while Fe₃Al is precipitated from solid solution over a wide temperature range. All the α-Fe and Fe₃Al particles/precipitates have the same orientation relationship with the β′-matrix. Fine coherent precipitates of Fe₃Al and α-Fe have been observed in quenched alloys. When the quenched alloys are tempered at temperatures between 400 and 500°C, the α-phase is precipitated from β′ and has a Widmanstätten morphology. The rates of coarsening of Fe₃Al and α-Fe precipitates appeared to be appreciably higher in the disordered β than in the ordered β′-phase.

MST/966