645 Volume 28 Issue 11 November 2007 Pages 645-648 International Scientific Journal published monthly as the organ of the Committee of Materials Science of the Polish Academy of Sciences Archives of Materials Science and Engineering ' Copyright by International OCSCO World Press. All rights reserved. 2007 Microstructure studies of ball milled and vacuum hot pressed NiZrTiAl powders J. Dutkiewicz a, *, W. Maziarz a , L. Litynska a , M. MolnÆrovÆ b , A. KovÆLovÆ b a Institute of Metallurgy and Materials Science of Polish Academy of Sciences, ul. W. Reymonta 25, 30-059 Krakw, Poland b Department of Metal Forming, Faculty of Metallurgy, Technical University of Koice, VysokokolskÆ 4, 042 00 Koice, Slovakia * Corresponding author: E-mail address: nmdutkie@imim-pan.krakow.pl Received 01.10.2007; published in revised form 01.11.2007 ABSTRACT Purpose: To determine microstructure and hardness of hot pressed mechanically alloyed MA NiZrTiAl powders well known as a good glass formers. Design/methodology/approach: Powders has been ball milled r 40 hours starting from pure elements. Changes of particles size and crystallographic structure of nanocrystals embedded in the amorphous matrix during milling has been determined using High Resolution Transmission Electron Microscopy HRTEM. Findings: The MA particles first grow, then decrease after 40 hours of milling, when powders possess amorphous structure. HRTEM studies of powders allowed to reveal small nanocrystals of NiTi 2 within milled powders which were not detected using X-Ray diffraction. The powders show crystallization peak at temperature T x near 553C. Consolidation of powders was performed under vacuum using uniaxial hot pressing method at temperature slightly below T x . Mean microhardness was determined near 430 HV and the mean Young·s modulus as 81 GPa. Practical implications: It was shown a possibility of hot densification in vacuum of amorphous Ni base alloys allowing to obtain bulk amorphous compacts with embedded nanocrystals. Originality/value: The size and structure of nanmocrystals within the amorphous matrix after MA and after hot vacuum densification has been determined. The microhardness and Youngs modulus of compacts show perspectives of application of such materials. Keywords: Amorphous metals; Metallic glasses; Ni- based alloys; Mechanical alloying MATERIALS 1. Introduction Ni based amorphous alloys (Ni 50 at.%) have been considered as potential engineering materials with good mechanical properties, particularly high elastic limit. Many binary, ternary and higher order of Ni based amorphous alloys have been prepared by rapid quenching techniques [1,2]. However, only a few Ni based amorphous alloys have the undercooled liquid region (URL) that relates to thermal stability of the amorphous alloy [3,4]. These new alloys are expected to expand the application fields of bulk amorphous alloys due to the unique properties, such as high tensile strength and relatively high corrosion resistance at room temperature [5]. The supercooled liquid region is defined by temperature range, T = T x - T g , between the glass transition temperature (T g ) and crystallization temperature (T x ). The increase of T means that stability of the supercooled liquid state increases against crystallization and therefore enables formation of bulk amorphous alloys by conventional casting techniques at low cooling rates ranging from 1.5 to 100 Ks -1 [4]. Recently, new metallic amorphous alloys with a wide supercooled liquid region exceeding 20 K have been prepared in a number of Ni based alloy systems, such as Ni 76 M 5 P 19 (M = Ti, Zr, Hf or Nb), Ni 75-x Nb 5 M x P 20-y B y (M = Cr, 1. Introduction