Extrusion of EN AW-2014 alloy in semisolid state

Abstract

The potential of forming EN AW-2014 alloy in semisolid state was investigated. The EN AW-2014 slugs were partially melted at 610°C, to a liquid fraction of ∼15, before they were extruded into a solid bar with a diameter of 16 mm. The ram speed used in this process was much lower than that employed in thixoforging of the same alloy to maximise heat removal from the slug and to fully solidify the liquid fraction by the time the extruded bar exits the die. The high solid fraction employed was also of help in this regard. Forming during extrusion under these conditions took place largely via rotation of the α-Al globules over one another, producing a remarkable microstructure of predominantly uniform globular α-Al grains. The forming load was at least an order of magnitude smaller with respect to that measured during hot extrusion of the same alloy, underlining the benefits of extruding the hard to form 2XXX alloys in semisolid state. Having been largely drained of its liquid, the final part of the preheated slug, however, failed to enjoy extrusion under such favourable conditions. The large extrusion deformation and temperatures well above the liquidus point have led to dynamic recrystallisation, which is responsible for the equiaxed, instead of fibrous, grain structure in this region.

An Investigation on the Effects of Pre-deformation and Temperature on Thixotropic Microstructure of AA2014 Aluminum Alloy

“…However, much of the melting occurred above 600°C in spite of a wide melting temperature interval. Semi-solid processing is often carried out with as much as 30-50 % liquid in the feedstock [11] under a closed die cavity. The sensitivity of the liquid fraction to temperature change across the corresponding temperature range, 623-631°C, is too high (dF L /dT [ 1.5°C -1 ) to carry out the process without an under die supporting.…”

“…During this stage, solid and liquid phases of the alloy coexist in equilibrium [6]. In order to achieve globular and non dendritic microstructure, several methods have been investigated such as electromagnetic stirring of the liquid in solidification [8], direct spheroidization of dendritic; cold deformed structures [9] or submitted to some particular complex thermo mechanical treatments like SIMA process [10,11].…”

Heat treatment of thixoformed EN AW 7075 alloy

“…[1][2][3][4] While forging is the most popular manufacturing route for shaping EN AW 7075 parts, there is growing interest in forming this alloy in the semisolid state [5][6][7] due to the difficulties involved in forming high strength wrought aluminium alloys with conventional processes. [8][9][10] Semisolid forming, on the other hand, offers to improve the overall quality of the part with considerable cost savings and without a sacrifice in mechanical properties. [11][12][13][14] Thermomechanical processing has been the predominant method to produce thixotropic feedstock for the semisolid forming of various otherwise wrought aluminium alloys.…”

Manufacturing of Al-Zr Thermal-resistant Alloys for Transmission Lines

“…During extrusion and cold drawn processing the existence of ne spherical and metastable Al 3 Zr phases were the most eective dispersoids of to prevent recrystallization in the aluminum alloy [17]. The inhibitor characteristics of it is explaned by pinning the grain boundaries [18]. 4.…”