Mechanical Properties of Al-Si-Mg Alloy Castings as a Function of Structure Refinement and Porosity Fraction

Abstract

During design of the casting products technology, an important issue is a possibility of prediction of mechanical properties resulting from the course of the casting solidification process. Frequently there is a need for relations describing mechanical properties of silumin alloys as a function of phase refinement in a structure and a porosity fraction, and relations describing phase refinement in the structure and the porosity fraction as a function of solidification conditions. The study was conducted on castings of a 22 mm thick plate, made of EN AC-AlSi7Mg0,3 alloy in moulds: of quartz sand, of quartz sand with chill and in permanent moulds. On the basis of cooling curves, values of cooling rate in various casting parts were calculated. The paper also presents results of examination of distance between arms in dendrites of a solid solution α (DASL), precipitations length of silicon in an eutectic (DlSi) and gas-shrinkage porosity (Por) as a function of cooling rate. Statistical relations of DASL, DlSi, Por as a function of cooling rate and statistical multiparameter dependencies describing mechanical properties (tensile strength, yield strength, elongation) of alloy as a function of DASL, DlSi and Por are also presented in the paper.

Influence of the Chemical Composition on Electrical Conductivity and Mechanical Properties of the Hypoeutectic Al-Si-Mg Alloys

“…It may also be attributed to the increasing volume fraction of the alloys porosity. With the increasing porosity alloys mechanical properties decrease [5,26]. The addition of silicon suppress formation of significant volumetric shrinkage, however, it leads to the increase of microshrinkages, evenly distributed within the whole volume of the material.…”

Validation Tests of Prediction Modules of Shrinkage Defects in Cast Iron Sample

“…Properties of the mould sand were preliminarily assumed from the database developed in earlier tests [2,13]: thermal conductivity = 0,7 W/mK, specific heat = 1000 J/kgK, density = 1500 kg/m 3 ). Real solidification time about 500 seconds was achieved in a satisfying way for both codes (underestimation error was about 5%).…”

“…Shr -percentage discontinuity related to volume of the whole specimen (equal to volume shrinkage of the studied cast iron in defined conditions); compacted -density of an alloy, by assumption -alloy of perfect compactness, in described tests this value was approximated based on routine density study [13] of a specimen cut out of a chill interaction zone, g/cm 3 ,  -density of a specimen determined using the formula (1). In parallel, to determine volume of the compacted shrinkage cavity, a certain method was applied (further known as SMBShrinkage Method Bis).…”

Possibility of Utilization of Gate Geometry to Modify the Mechanical and Structural Properties of Castings on the Al-Si Basis

“…Prediction of mechanical properties of the casting when designing the structure of the gate system and the technology of production should be based on the relations between the mechanical properties of the alloy with the relevant parameters of crystal structure and fractions of gas bubbles which are bound to porosity. Decreased quality caused by air retention in the volume of the castings becomes evident especially when the mechanical properties and machinability are decreased [1][2][3].…”