AbstractThe microstructures of Ti–Al layers produced by laser surface alloying of a Ti substrate have been investigated for Al contents in the range 17–36 at.–%. The alloyed layers were obtained using a continuous wave CO2laser and a powder feed technique employing the following laser processing parameters: 1·8 kW power, 3 mm beam diameter, 7 mm s−1traverse speed, and feedrates of Al powder ranging from 0·03 to 0·07 g s−1. The microstructures were disordered lath martensiteα′in 17 at.–%Al alloy, ordered massive and acicular martensite in 23 at.–%Al alloy, and ordered massive, acicular, and lath martensite in 30 and 36 at.–%Al alloys. The change in martensite type and morphology is discussed in relation to the available datafor theβtoα′transformation in Ti alloys.MST/1437