Martensite formation in Ti–Allayers produced by laser surface alloying

Abstract

The 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 CO₂ laser and a powder feed technique employing the following laser processing parameters: 1·8 kW power, 3 mm beam diameter, 7 mm s ⁻¹ traverse speed, and feedrates of Al powder ranging from 0·03 to 0·07 g s ⁻¹. The microstructures were disordered lath martensite α′ 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 the β to α′ transformation in Ti alloys.

MST/1437