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2 2019

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The Study of the Tensile Strength of AlSi21CuNiMg Silumin in the Final Stage of Solidification and the Initial Stage of Cooling

Romankiewicz Remigiusz

Journal of Casting & Materials Engineering

2019

Vol. 3, no. 3

57--61

The paper presents the results of tensile strength tests of AlSi21CuNiMg silumin made on a test stand. Silumin was under examination in an unmodified state and after modification with AlCu19P1.4 master alloy in quantity of 0.2% in relation to the mass of the alloy. Using a scanning microscope, the surface fractures obtained from tensile tests were tested. The structure and profiles of fractures were examined using an optical microscope. Modification of the tested silumin resulted in a favorable fragmentation and regular distribution of the crystals of the primary silicon in the alloy structure, which led to an almost twofold increase in the strength of the silumin samples at the final solidification stage from 3.5 to 6.6 MPa. As a result of these changes, the resistance of silumin to hot cracks should increase, which is of great importance when casting hypereutectic silumin in a metal mould that strongly inhibits the shrinkage of the castings.

Hard Inclusions in Armature Brass

Romankiewicz Remigiusz, Romankiewicz Ferdynand

Journal of Casting & Materials Engineering

2019

Vol. 3, no. 3

51--56

The influence of the chemical composition of selected armature brasses on the formation of hard inclusions was investigated. In metallographic studies using optical microscopy and scanning electron microscopy with X-ray microanalysis (EDS), it was found that hard inclusions attain sizes ranging from several hundred nanometers to several micrometers. Investigations of samples that were taken from metallurgical pigs of armature brass of various chemical compositions have shown that the contribution of components such as iron and silicon have a decisive influence on the formation of hard inclusions. These components have a dominant share in hard inclusions (60–76 wt.% Fe and 10.6–17.4 wt.% Si). In much smaller quantities there are also elements such as manganese, phosphorus, nickel and chromium. The chemical composition of hard inclusions varies. The number and size of hard inclusions depends on the contribution of iron and silicon brass. In the brass sample with 0.31 wt.% Fe and 0.08 wt.% Si, 1183 inclusions per square millimeters were identified, while in the brass sample with 0.21 wt.% Fe and 0.11 wt.% Si the amount of hard inclusions was reduced to 933 inclusions per square millimeters. In the brass sample with reduced iron content up to 0.08 wt.% and silicon up to 0.006 wt.%, no hard inclusions were identified.