Analysis of solidification in Bridgman furnace as simulation of DC casting of aluminium alloy slabs

Abstract

The vertical Bridgman directional solidification equipment has been used in several investigations to simulate direct chill casting of wrought aluminium alloys. As a basis for such investigations and alloy developments, it is important to have an understanding of the performance of the furnace used during simulation of the casting conditions. In this investigation the thermal conditions in the furnace have been analysed in detail, both by measurements and by mathematical modelling. The growth characteristics of the furnace, such as gradient, growth rates and cooling rates have been compared to conditions in large ingots. The direct chill casting conditions, which the simulations have been compared to, are casting of slabs of 330 and 600 mm thickness of an aluminium AA3003 type alloy. The results show that the experiments are able to simulate the cooling conditions in the ingots except from the surface zone. Comparisons of the microstructures have been made and a good agreement has been obtained for structure parameters such as grain size and DAS.

Method Developed for Quantitative Analysis of Inclusions in Solidified Aluminum Ingots

“…[10] The present work has developed a simpler test for inclusion assessment in solidified aluminum castings, using an NaOH deep-etching technique. [20] One reason for using the deep-etching method concerns the random occurrence of inclusions in Al ingots; another reason concerns the difficulty of applying the available detection and quantitative assessment techniques. Furthermore, the actual distribution of inclusions in final castings should be known, not only their occurrence in the melt, which is possible with the new technique.…”

Analysis of Distribution of Nonmetallic Inclusions in Aluminum DC-Cast Billets and Slabs

“…The inclusion content is described in terms of the number of etch pits, which can be counted visually or using an image analysis program. [2] A detailed description, analysis, and validation of the technique is presented in Jaradeh and Carlberg. [3] From the studied etched slices, selected 5 9 10-mm samples were cut for microscopic observation.…”

“…Using a newly developed deep-etching test [2,3] that allows quick determination of the inclusions in large specimens, such information is now available. Knowledge of the inclusion content and size distribution in solidified Al castings is particularly important for subsequent processing, extrusion, and rolling.…”

Silicon crystal morphologies during solidification refining from Al–Si melts

“…The samples were 115 mm in length and were inserted into 5 mm inner diameter alumina tubes. Detailed experimental procedures and furnace descriptions are given in previous papers [7,8]. The furnace setup was arranged for growth antiparallel and parallel to the gravity vector, i.e.…”

“…The furnace was pulled at 40 mm in most cases and the samples were subsequently quenched. The temperature gradient inside the samples was 48 1C/cm at the quenching position under the hot zone up condition [8].…”