Influence of microstructure parameters of [Al – FeCr] cast composite material, obtained in the “volume” of foundry mold using lost-foam casting process, on its mechanical characteristics

Abstract

The authors conducted an in-depth analysis of domestic and foreign literary data, as well as formulated and set the goal of this scientific work. The inoculation of cast Al-based alloy of the AK12 DSTU 2839:1994 with dispersed intermetallic FeCr in the “volume” of the casting mold (CM) during casting by using of Lost-foam casting (LFC-process) allowed to get samples of zero-dimensional cast composite material (CCM) of the system [Al – FeCr]. Metallographic analysis (MGA) showed that the parameters of the microstructure, such as the specific number of σ-phase inclusions and its dispersion, can vary not only along the height of the cast samples, but are also dependent on each other. Mechanical tests of the obtained material showed that not only the height of the composite casting, but also the parameters of its microstructure affect the temporary resistance to rupture, relative elongation and hardness on the Brinell scale. The application of MGA and mechanical tests for the zero-dimensional CCM of the system [Al – FeCr] and, accordingly, for the control casting showed experimentally what a decrease in the average dispersion of σ-phase inclusions from 26.6 μm to 57.1 μm leads to the fact that the temporary resistance to rupture and the relative elongation of the investigated composite decrease from 135 MPa and 2.5 % to 60 MPa and 0.5 %, respectively. At the same time, the increase in the hardness of samples of the zero-dimensional CCM system [Al – FeCr] from 6.923×10-1 GPa to 7.885×10-1 GPa on the Brinell scale is a consequence of the fact that the average dispersion of σ-phase inclusions in the structure of the studied composite decreases from 26.6 μm to 57.1 μm. The results of the conducted research also made it possible to find out that the increase in the specific number of σ-phase inclusions from 63 mm-2 to 263 mm-2 is the reason for the increase in the temporary resistance to rupture and the relative elongation of the zero-dimensional CCM of the system [Al – FeCr] from 60 MPa and 0.5 % up to 135 MPa and 2.5 %, respectively. However, the hardness of the composite casting, which was determined according to the Brinell scale, and under the condition that the specific number of σ-phase inclusions in the structure of the zero-dimensional CCM of the system [Al – FeCr] is in the range given above, as a result decreases from 7.885×10-1 GPa to 6.923×10-1 GPa.