Peculiarities of ball-milling induced crystalline-amorphous transformation in Cu-Zr–Al-Ni-Ti alloys K.Tomolya 1 , D.Janovszky 1a , A.Sycheva 1 , M.Sveda 1 , T.Ferenczi 2 , A.Roósz 1 1 MTA-ME Materials Science Research Group, Miskolc, Hungary 2 University of Miskolc, Miskolc, Hungary a Corresponding author: fekjd@uni-miskolc.hu Abstract An amorphization process in (Cu 49 Zr 45-x Al 6+x ) 100-y-z Ni y Ti z (x=1, y,z=0;5;10) induced by ball- milling is reported in the present work. The aim was investigation of the effect of Ni and Ti addition to Cu 49 Zr 45 Al 6 and Cu 49 Zr 44 Al 7 based alloys as well as type of initial phases on the amorphization processes. Also the milling time sufficient for obtaining fully amorphous state was determined. The entire milling process lasted 25 hours. Drastic structural changes were observed in each alloy after first 5 h of milling. In most cases, after 15 h of milling the powders had fully amorphous structure according to XRD except for those ones, where TEM revealed a few nanosized crystalline particles in the amorphous matrix. In (Cu 49 Zr 45 Al 6 ) 80 Ni 10 Ti 10 alloy the amorphization process took place after 12 h of milling and the amorphous state was stable up to 25 h of milling. In the case of (Cu 49 Zr 44 Al 7 ) 80 Ni 10 Ti 10 alloy the powders have fully amorphous structure between 12 h and 15 h of milling. Keywords: amorphous powder, Cu-Zr-Al alloy, ball-milling, microstructure 1. Introduction It is well known that industry expects development of new stronger and lighter materials from materials science. So bulk metallic glasses (BMGs) have been extensively studied nowadays. Despite excellent mechanical properties of BMGs, the high-volume industrial application has not yet become a reality. Production of BMGs with greater than 1 dm in size is not solved; only some Pt and Pd-based alloys and Zr-based 1-2, Cu-based 3-4 and Ti-based 5-6 BMGs have been produced with few cm sizes only. The powder metallurgy (PM) can solve this problem via consolidation of amorphous powders 7-9. The first step of PM is manufacturing amorphous powders by high-pressure gas atomization or by solid state techniques, e.g. high energy ball-milling. Recently, Cu-Zr based BMGs 10-11 have attracted great attention due to high strength and high thermal stability against crystallization with lower costs than Zr-based BMGs. Cu-Zr-Al BMGs 12-16 have such advantageous properties as good toughness indicated by their high Charpy impact value, good corrosion resistance, and high glass forming ability (GFA). However, their plasticity at room temperature is usually less than 2 % compared with that of BMGs in the Zr–Ni–Al and Zr– Al–Ni–Cu systems [17-18]. Ni and Ti form a complete solid solution with Cu and Zr. In the Cu-Zr-Al-Ni-Ti system, the heat of mixing between elements is negative; only in the case of Ni-Cu (H mix = 4 kJ/mol 19) it is positive. In the Cu-Zr-Al system, two compositions with high glass forming ability 20 were selected as basic alloy (Cu 49 Zr 45 Al 6 and Cu 49 Zr 44 Al 7 ) and Ni and Ti were added as alloying elements. In this work, the structure evolution of alloyed (Cu 49 Zr 45-x Al 6+x ) 100-y-z Ni y Ti z (x=1, y,z=0;5;10) powders was investigated. The aim of the present work is to create alloys in this composition system with fully amorphous structure via high energy ball-milling. It is well known that the progress of amorphization reaction is a recycling process (crystalline-amorphous-crystalline).