AbstractThe microstructures of extruded high tensile brasses with compositions conforming to BS 2872/4 CZ114, CZ115, and CZ116 consist of copper rich fccα-phase, ordered B2β′-phase, and some iron rich particles; these particles areα-Fe in alloy CZ115 and Fe3Al in alloy CZ116. Alloy CZ114 contains mainlyα-Fe particles, although a few, small precipitates of Fe3Al have also been observed. It is shown in studies of the microstructural development that theα-Fe particles are formed in the liquid, while Fe3Al is precipitated from solid solution over a wide temperature range. All theα-Fe and Fe3Al particles/precipitates have the same orientation relationship with theβ′-matrix. Fine coherent precipitates of Fe3Al andα-Fe have been observed in quenched alloys. When the quenched alloys are tempered at temperatures between 400 and 500°C, theα-phase is precipitated fromβ′and has a Widmanstätten morphology. The rates of coarsening of Fe3Al andα-Fe precipitates appeared to be appreciably higher in the disorderedβthan in the orderedβ′-phase.MST/966