An Analytical Approach for the Correlation Between Bifilm Index and Tensile Properties of AlSi7Mg0.3 (A356) Aluminum Alloy Cleaned via Rotary Degassing and Different Fluxes

Abstract

Mechanical properties of the castings are directly affected negatively by the inclusions, such as its own oxide occurring during melting, if proper and logical liquid metal processes could not be carried out. To overcome this issue, different compositions and types of fluxes were practiced. Na2SiF6, NaF/AlF3 (cryolite ratio) = 1.85, 2.8, and 3, NaF, Na3AlF6 (commercial cryolite) added with different ratios to the mixture of NaCl+KCl, and also only Na2SiF6 to the mixture of MgCl2+KCl were appended to the liquid metal to remove inclusions, such as old oxide bifilms. Average effectiveness values of the fluxes concerning mechanical properties were investigated as well. The change in the melt cleanliness before and after degassing has been taken into account to establish a model that correlates bifilm index and tensile properties. Since bifilm index is directly interested in porosity shape and amount to quantify liquid metal quality, any other techniques, such as density index, were not be consulted. In addition, the main focus was based on how much the melt was cleaned rather than the cleanliness of the melt after degassing. Thus, the difference of bifilm index as a melt cleanliness indicator firstly was introduced to the literature. In addition to this, the contour plots of mechanical properties and bifilm index values were used to evaluate the correlation, and it was found that there was an exponential relationship, a quality index, between elongation at fracture, tensile strength, and bifilm index.