Abstract
A novel processing method for amorphous Al50Ti50 alloy, obtained by mechanical alloying and subsequently consolidated by electrical resistance sintering, has been investigated. The characterisation of the powders and the confirmation of the presence of amorphous phase have been carried out by laser diffraction, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The amorphous Al50Ti50 powders, milled for 75 h, have a high hardness and small plastic deformation capacity, not being possible to achieve green compacts for conventional sintering. Moreover, conventional sintering takes a long time, being not possible to avoid crystallisation. Amorphous powders have been consolidated by electrical resistance sintering. Electrically sintered compacts with different current intensities (7–8 kA) and processing times (0.8–1.6 s) show a porosity between 16.5 and 20%. The highest Vickers hardness of 662 HV is reached in the centre of an electrically sintered compact with 8 kA and 1.2 s from amorphous Al50Ti50 powder. The hardness results are compared with the values found in the literature.
Highlights
Al-Ti crystalline alloys are very attractive low-density materials with excellent properties at high temperatures [1]
After 75 h of milling, the crystalline phase has totally disappeared of the material
A novel method of compacts processing of the Al50 Ti50 alloy obtained by mechanical alloying and subsequent consolidation by ERS has been investigated
Summary
Al-Ti crystalline alloys are very attractive low-density materials with excellent properties at high temperatures [1]. These techniques take advantage of the Joule heat generated by the passage of an electric current through the powder mass One of these techniques, Spark Plasma Sintering (SPS), has recently been applied to mechanically alloyed Al86 Ni8 Y6 amorphous powders [8,9] reaching temperatures of up to 400 ◦ C for a relatively long time in the order of minutes. Combined electric current with pressure, and Taylor [12] added the use of capacitors to eliminate the oxides covering the metal powders These techniques are a type of hot pressing in which the powder itself generates heat due to the Joule effect, and are called “electrical resistance sintering under pressure”. Amorphous Al50 Ti50 alloy is prepared by MA and the effect of different parameters of the ERS process on porosity, microstructure, formation of intermetallic compounds, kinetics of devitrification and hardening are analysed
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