Present work was carried out to investigate the measurement accuracy of the sump depth for 7050 billet in direct chill (DC) casting process. Three measuring methods were applied: (i) Al-30wt.% Cu melt was poured into the mold at the steady state of the casting attempting to record the profile of billet sump; (ii) two steel rods were vertically dipped into the centreline and the edge of the billet attempting to measure the distances between the solidus and the free liquid surface in the hot-top; (iii) several ordered thermocouples were pre-arranged onto the starting block and they were solidified into the billet as it was cast, and a series of temperature-time curves was recorded after casting. For the purposes of comparison and evaluation, a numerical model based on the same experiment parameters was also built and the simulation results were compared with measured results by above methods. It indicates that the sump depth measured by thermocouples has the best consistency with numerical results. The most accurate method is temperature recoding by thermocouples. The Al-Cu melt pouring method is more accurate than the rods dipping method, and the sump depths measured by later two methods were the positions about the solid fraction (fs) depths of 0.8 to 0.9.
The selection of different processing parameters has an important influence on the microstructure and properties of castings. The aim of this investigation is to study the effect of the processing parameters of vacuum suction casting (VSC) on the microstructure and mechanical properties of the ZL116 aluminium alloy. The ZL116 aluminium alloy rods were prepared under an arc current of 300-400 A and a suction diameter of 3.0-3.5 mm using a vacuum-suction-casting machine. The microstructures of the alloys rods were observed with a scanning electron microscope (SEM). The mechanical properties of the alloy specimens were measured with a universal tension tester, a microhardness tester and an electrical resistivity tester. The experimental results show that the microstructure of the ZL116 aluminium alloy is more compact and uniform under an arc current of 300 A and a suction diameter of 3 mm. The mechanical properties and the electrical resistivity are also improved due to an increase of the strengthening phase. The microhardness reached 93.62 HV, the tension strength reached 199.79 MPa, and the total elongation at the breaking point reached 30.60 %.
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