168 Materials Science and Engineering, A 179/A 180 (1994) 168-172 A study of the glass-forming range in the ternary Ti-Ni-A1 system by mechanical alloying R. Nagarajan and S. Ranganathan Centre for Advanced Study, Department of Metallurgy, Indian Institute of Science, Bangalore .560 012 (India) Abstract The glass-forming range (GFR) in ternary Ti-Ni-Al alloys was determined via mechanical alloying using a high energy Spex mill. The GFR was also calculated using Miedema's model. Although the theoretical GFR is quite large, the experi- ments showed a very limited GFR. The concentration ranges chosen were TisoNixAls0_* (x = 10, 25, 40), Ti60Ni~Al4, , (y = 10, 20, 30), TiToNitsA115, NizTiA1 and TiNiAI. Prolonged milling of the amorphous TisoNi25A125powders led to the reappearance of the crystalline peaks. Calorimetric experiments showed an endothermic peak near 600 K in most of the samples. 1. Introduction Among non-equilibrium processing techniques, mechanical alloying has gained popularity over rapid solidification processing techniques in recent years since it promises the possibility of production in bulk amounts. Mechanical alloying is a solid state reaction process, where a large glass-forming range is achieved [1]. There are excellent proceedings available on the types of metastable microstructure that can form during mechanical alloying [2, 3]. Suryanarayana and co-workers [4, 5] have listed the various possible metastable microstructures in titanium base alloys achievable by rapid solidification process- ing and mechanical alloying. Considerable work has been reported on the mechanical alloying of Ti-Ni [6-8] and Ti-Al [9, 10] systems. The formation of nanocrystalline phases has been observed in these systems [11]. However, very few reports are available on ternary systems. Ti-Ni-Cu [8, 12-14], Ti-Cu-Pd [15] and Ti-Ni-A1 [16] have been studied. Detailed studies of both Ti-Ni [8, 17] and Ti-Ni-Cu [8] during mechanical alloying and rapid solidification processing have been carried out in our laboratory. The Ti-Ni-Cu system has a deep eutectic which suggests a large heat of mixing for the liquid. It showed a fairly large glass- forming range during mechanical alloying. Other than the binary intermetallic compounds, A16.sNiTi2. 5, Al2NiTi, AINiTi and A1Ni2Ti are present in the Ti-Ni-A1 system [18]. Itsukaichi et al. [16] determined the glass-forming range in the Ti-Ni-A1 system using a conventional ball mill. It was deduced that the composition close to Ti6vNi33 could be easily amorphized, whereas at com- positions close to the pure metals, the alloys give only solid solutions. Also, an AINi type structure is reported close to the A1Ni binary side. They reported a phase which has an f.c.c, structure (E93) similar to that of Ti2Ni in a vacuum hot pressed TisoNi25A125 sample. Since the Ti-Ni, A1-Ni and Ti-A1 binary systems have important intermetallic compounds, and since Ti-A1 and Ti-Ni show a wide range of amorphous phases during mechanical alloying, the Ti-Ni-AI system is an obvious choice for study of the glass- forming range. The model used by Murty et al. [8] was used to obtain the glass-forming range theoretically in the Ti-Ni-A1 system and this is compared with the experimental results of the present work obtained using a high energy Spex mill. 2. Experimental procedure High purity (greater than 99.95%) titanium, nickel and aluminium powders with particle sizes of approxi- mately 325 mesh (less than 45 × 103 nm) were used for our study. The powders were thoroughly mixed in a high energy Spex mill. This is a vibratory mill in which the vial vibrates in three mutually perpendicular direc- tions with an amplitude of 50 mm and a frequency of 20 Hz. The speed of the mill used was 1200 rev min- ~. Steel balls of 15 mm diameter were used and the ball to powder ratio taken was 8:1. The kinetic energy per ball is 0.14 J. 0921-5093/94/$7.00 © 1994 - Elscvier Sequoia. All rights reserved SSDI 0921-5093(93)05513-0