Grain Refinement of Al4CuTi Alloy with Zirconium, Scandium and Erbium

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Thesis Type: Postgraduate

Institution Of The Thesis: Karadeniz Technical University, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Turkey

Approval Date: 2018

Thesis Language: English

Student: Ahmad Sajjad

Supervisor: Ümit Alver

Open Archive Collection: AVESIS Open Access Collection

Abstract:

The purpose of this research work is to find an optimum grain refiner for Al4CuTi alloy by using Zirconium (Zr), Scandium (Sc) and Erbium (Er). A series of samples were casted with various proportions of Scandium and Erbium from 0.05 to 0.30 wt% while Zirconium percentage was fixed to 0.35 wt%. Samples were prepared by standard metallographic procedure and examined through optical microscope, scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS). It was observed that a combined addition of Zirconium and Scandium has a significant effect on grain refinement of Al alloys rather than Zirconium or Scandium alone. SEM results revealed that Scandium dissolved in Al3Zr phase instead of making an alternative layered structure of Al3Sc and Al3Zr, but it has a positive effect on the grain refinement. One of the most important ideas behind this research is to determine whether Erbium can be a replacement of expensive Scandium. Though Erbium performed steadily when used in an amount less than 0.2 wt % but it does not appear to replace Scandium as an efficient grain refiner because AlCuEr phase forms which did not act as active heterogeneous nucleation site and subsequently didn't facilitate the grain refinement phenomenon. A combination of 0.002 %TiB2 together with 0.1 wt%Sc and 0.15 wt%Er worked extreme well and reduced the grain size to our set target of 50 μm, which is the best outcome of this research.