Microstructural And Phase Analysis Of Al Based Bulk Metallic Glass Synthesized By Mechanical alloying And Consecutive Spark Plasma Sintering With Varying Consolidation Pressure  

Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India

Adv. Mater. Lett., 2016, 7 (3), pp 187-191

DOI: 10.5185/amlett.2016.6174

Publication Date (Web): Feb 01, 2016

Copyright © IAAM-VBRI Press

E-mail: laha@metal.iitkgp.ernet.in

Abstract

In the present work, Al₈₆Ni₈Y₆ and Al₈₆Ni₈La₆ powder blends were mechanically alloyed. Al₈₆Ni₈Y₆ yielded full amorphous structure (150 h); whereas Al₈₆Ni₈La₆ was partially amorphized after same duration of milling attributed to incomplete dissolution of solute ‘La’ in solvent ‘Al’. DSC experiment showed wider glass transition temperature range of ~ 44 ^oC (T_x - T_g = 268 ^oC-224 ^oC) in Al₈₆Ni₈Y₆ amorphous powders; whereas no glass transition temperature was detected in Al₈₆Ni₈La₆ powders. Further, Al₈₆Ni₈Y₆ amorphous powders were consolidated via spark plasma sintering in the pressure range of 100-400 MPa. XRD and TEM analysis confirmed retention of larger fraction of amorphous phase in higher pressure sintered sample, attributed to suppression of mass transfer diffusion kinetics process. Higher pressure favored short range ordering leading to formation of various intermetallic phases; whereas comparatively faster diffusion in case of low pressure sintering promoted long range ordering forming nanocrystalline FCC-Al. Higher sintering pressure (say 400 MPa) consolidated sample resulted in better densification (~ 99 %) with improved inter-particle bonding and moreover, retention of larger volume fraction (~ 92 vol %) of amorphous phase with intermetallic nano-precipitates. Vickers microhardness test showed improvement in hardness with increasing sintering pressure attributed to higher fraction of retained amorphous phase and better inter-particle bonding.

Keywords

Al based amorphous alloy, mechanical alloying, spark plasma sintering, sintering pressure,microstructural evolution.