The glass forming ability and crystallization behaviour of melt spun Ti 5 0 - x Cu 2 5 Ni 1 5 Sn 3 Be 7 Zr x (x = 0, 3 and 5) amorphous alloys were investigated using differential scanning calorimetry (DSC), X-ray diffractometry and transmission electron microscopy. With increasing Z r contents, x from 0 to 5, ? T x (= T x - T g ) and T r g (= T g T l ), where T g = glass transition temperature, T x = crystallization temperature and T l = liquidus temperature, gradually increase from 45 K to 56 K and from 0.57 to 0.60, respectively. The Ti 5 0 Cu 2 5 Ni 1 5 Sn 3 Be 7 alloy shows three exothermic events in the DSC curve; initially the alloy crystallizes by forming a few nanometer scale crystalline phase, followed by decomposition into a mixture of Ti(Ni,Cu), TiCu, Ti 3 Sn, and TiBe 1 2 phases at high temperature. Furthermore, the alloys containing Zr exhibit the formation of nanocrystalline phases of ~10 nm size even after the second exothermic event due to their increased atomic packing density. For the Ti 4 5 Cu 2 5 Ni 1 5 Sn 3 Be 7 Zr 5 alloy, fully amorphous rods up to 5 mm in diameter were successfully fabricated by injection casting.
L'aptitude a la vitrification et le comportement en cristallisation d'alliages amorphes trempes sur rouleau Ti 5 0 - x Cu 2 5 Ni 1 5 Sn 3 Be 7 Zr x (x = 0, 3 et 5) ont ete etudies par calorimetrie differentielle a balayage (DSC), diffractometrie de rayons X et microscopie electronique en transmission. Lorsque la teneur x en zirconium augmente de 0 a 5, ? T x (= T x - T g ) et T r g (= T g /T l ), ou T g = temperature de transition vitreuse, T x = temperature de cristallisation et T 1 = temperature du liquidus, augmentent graduellement, respectivement de 45 K a 56 K et de 0,57 a 0,60. L'alliage Ti 5 0 Cu 2 5 Ni 1 5 Sn 3 Be 7 presente trois evenements exothermiques sur la courbe de DSC; initialement l'alliage cristallise en formant une phase cristalline de taille nanometrique, puis se decompose a haute temperature en un melange de phases Ti(Ni,Cu), TiCu, Ti 3 Sn et TiBe 1 2 . De plus, les alliages contenant du zirconium presentent une formation de phases nanocristallines de taille ~10 nm meme apres le deuxieme evenement exothermique, a cause de leur plus grande densite d'empilement atomique. Pour l'alliage Ti 4 5 Cu 2 5 Ni 1 5 Sn 3 Be 7 Zr 5 , des barreaux de diametre atteignant 5 mm ont pu etre produits par coulee en injection.