Production of glassy metallic layers by laser surface treatment F. Audebert a, * , R. Colac ßo b , R. Vilar b , H. Sirkin a a Facultad de Ingenier  ıa, Universidad de Buenos Aires, Paseo Col on 850, (1063) Buenos Aires, Argentina b Dep. Eng. de Materiais, Instituto Superior T ecnico, Av. Rovisco Pais 1049-001 Lisboa, Portugal Received 10 April 2002; accepted 13 August 2002 Abstract This work aims to investigate if glassy surface layers can be obtained when glass forming alloys are submitted to laser surface treatment techniques. Three types of alloys, with different glass forming abilities, were investigated: Zr-, Mg- and Al-based alloys. X-ray diffraction analysis shows that vitreous phases can be formed in the Zr- and Mg-based alloys, when the treatments are made using laser scanning speeds larger than 2 m/s. Ó 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. Keywords: Laser surface treatment; Amorphous layers 1. Introduction Glassy metals are known by their high hardness and excellent corrosion resistance in several chemical environments [1,2]. Consequently, the production of this type of materials in the form of coatings or surface layers can be an interesting technological achievement for the wide range of applications in which wear and corrosion resis- tance is a main requirement. However, the high quenching rates necessary for the formation of the vitreous phase are an important limitation for the production of glassy surfaces [3,4]. Laser surface treatment (LST) techniques, such as laser surface melting, laser alloying and laser cladding, provide a wide range of interesting solu- tions for the production of wear and corrosion resistant surfaces. With LST techniques, the sur- face may be coated with a layer of another mate- rial by laser cladding [5], the composition of the matrix can be modified by laser alloying [6] and, more importantly for the case under analysis, high quenching rates can be obtained by laser surface melting at high laser scanning speeds [7]. Previous works have shown that these characteristics of LST allow the formation of quasicrystalline [8] and amorphous phases [9,10]. Nevertheless, these pre- vious works have also shown that LST techniques present two majors drawbacks for obtaining fully glassy metallic layers: (i) the reheating cycle caused by the successive laser tracks can lead to the crys- tallization of the amorphous layer; (ii) the liquid is in contact with the crystalline solid substrate, which favors kinetically the crystalline phase, since growth of the crystal can occur simply by epitaxial solidification, avoiding the nucleation step. The recent discovery [11] of a group of metallic alloys that vitrify at quench rates much slower than the quench rates of traditional glassy metals Scripta Materialia 48 (2003) 281–286 www.actamat-journals.com * Corresponding author. Fax: +54-11-4331-1852. 1359-6462/03/$ - see front matter Ó 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. PII:S1359-6462(02)00382-2