Effects of Process Parameters on Shrinkage Porosity in 357 Semi-Solid Die Casting Parts

The shrinkage porosity that was caused by the insufficient feeding during solidification, was a common defect in the semi-solid die casting process. This defect decreased significantly the mechanical properties of the casting. In order to avoid the shrinkage porosity in casting, the die design, slug preparation and die casting process were carefully considered. In this study, a designed mold was used to make the sequential solidification of the slug. The process parameters, including intensification pressure, die temperature and biscuit thickness of the casting, were studied to show their influence on shrinkage porosity defects. The experimental results show that the high intensification pressure, high die temperature and long biscuit can be beneficial to obtain castings with no shrinkage porosity.

Slurry Preparation and Hot Tearing Susceptibility of A201 Aluminum Alloy in Rheological Die Casting

A201 alloy is the strongest cast aluminum alloy, but it is considered one of the most difficult aluminum alloys to cast due to its susceptibility to hot tearing during solidification. Semi-solid casting, which characterizes fine near-globular or non-dendritic grains and relatively narrow solidification range, is potential to reduce hot cracking tendency of alloys. In this present work, semi-solid slurries of A201 alloy were prepared using Swirled Enthalpy Equilibrium Device (SEED) technique and then injected into a self-designed high pressure hot tearing mold. The microstructures of A201 semi-solid slurries with different pouring temperatures were examined. Effects of different casting pressures on the hot tearing sensitivity of A201 have been investigated. This study finds that SEED is capable of producing satisfying A201 semi-solid slurries. Lower pouring temperatures produce A201 semi-solid slurries with finer and rounder grains as well as more uniform microstructure distribution. Increasing the intensification pressure significantly decreases the hot treating tendency of A201 alloy. When the pressure reaches to 90 MPa and the mold temperature of about 250 °C, the hot tearing susceptibility (HTS) index value is nearly zero, which means almost no surface cracks are found in the semi-solid A201 die casting parts.

Impact of Intensification Pressure and Grain Refiner on the Hot Tearing Susceptibility of a Semi-Solid Cast Al-Zn-Mg-Cu Alloy

The commercial application of wrought aluminum alloys to semi-solid casting would be extremely beneficial, as wrought alloys often exhibit better strength-ductility combinations than cast aluminum alloys. Semi-solid casting typically reduces the hot tearing tendency, as it requires a globular microstructure and produces grain refinement, but hot tearing often still occurs during the semi-solid die casting of complex-shaped components produced from wrought alloys. This study examined the impact of intensification pressure and grain refinement on the hot tearing tendency of an Al-Zn-Mg-Cu alloy. Semi-solid slurries were produced using the SEED (Swirled Equilibrium Enthalpy Device) process. A specially designed constrained rod mold was used to evaluate hot tearing. Results showed the tendency for hot tearing decreased with increasing of intensification pressure. Grain refinement (with 0.06Ti) was also found to be beneficial to the elimination of hot tearing.

Correlations between Defect Content, Mechanical Properties and Fractographic Investigation of AlSi9Cu3(Fe) Alloy Reference Castings

High Pressure Die Casting (HPDC) is a foundry process particularly suitable for high production rates and applied in several industrial fields, but the amount of scrap, caused by defects or incomplete filling, is sometimes very high. Thus it is important to know which are the main causes of defect formation and their effects on microstructure and mechanical properties. This paper presents, within the European MUSIC project, the qualitative and quantitative results of a study conducted on AlSi9Cu3(Fe) alloy castings, referred to as Horse-shoe Reference Castings, specifically designed to generate different kinds of defects with different severity levels. The work focuses on the correlations obtained between the casting mechanical properties, their defect content in terms of porosity and oxide films and the process parameters adopted, mainly second phase plunger velocity and intensification pressure. The three point bending test was carried out on the four specimens obtained from the two appendixes of the casting. The fracture surfaces were studied by scanning electron microscopy (SEM) and optical microscopy (OM) highlighting that the defect content is clearly correlated to the mechanical properties and the process parameter settings.

The Influence of Pressure Die Casting Parameters on the Castability of AlSi11-SiCp Composites

The paper presents the method of preparing a composite slurry composed of AlSi11 alloy matrix and 10 vol.% of SiC particles, as well as the method of its high-pressure die casting and the measurement results concerning the castability of the obtained composite. Composite castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. There were found the regression equations describing the change of castability of the examined composite as a function of pressure die casting process parameters. The conclusion gives the analysis and the interpretation of the obtained results.

Tribological Properties of AlSi11-SiCp Composite Castings Produced by Pressure Die Casting Method

The measurement results concerning the abrasive wear of AlSi11-SiC particles composites are presented in paper. The method of preparing a composite slurry composed of AlSi11 alloy matrix and 10, 20% vol.% of SiC particles, as well as the method of its high-pressure die casting was described. Composite slurry was injected into metal mould of cold chamber pressure die cast machine and castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. Very good uniform arrangement of SiC particles in volume composite matrix was observed and these results were publicated early in this journal. The kinetics of abrasive wear and correlation with SiC particles arrangement in composite matrix were presented. Better wear resistance of composite was observed in comparison with aluminium alloy. Very strong linear correlation between abrasive wear and particle arrangement was observed. The conclusion gives the analysis and the interpretation of the obtained results.

Correlations Between Arrangement of Reinforcing Particles and Mechanical Properties in Pressure Die Cast AlSi11-SiC Composites

The work presents the investigation results concerning the structure of composite pressure die castings with AlSi11 alloy matrix reinforced with SiC particles. Examination has been held for composites containing 10 and 20 volume percent of SiC particles. The arrangement of the reinforcing particles within the matrix has been qualitatively assessed in specimens cut out of the castings. The index of distribution was determined on the basis of particle count in elementary measuring fields. The tensile strength, the yield point and elongation of the obtained composite were measured. Composite castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. The regression equation describing the change of the considered arrangement particles index and mechanical properties were found as a function of the pressure die casting parameters. The infuence of particle arrangement in composite matrix on mechanical properties these material was examined and the functions of correlations between values were obtained. The conclusion gives the analysis and the interpretation of the obtained results.

Distribution of Reinforcing Particles in the Pressure Die Cast AlSi11/20% Sic Composite

A method of pressure die casting of composites with AlSi11 alloy matrix reinforced with 20 vol. % of SiC particles and the analysis of the distribution of particles within the matrix are presented. The composite castings were produced at various values of the piston velocity in the second stage of injection, at diverse intensification pressure values, and various injection gate width values. The distribution of particles over the entire cross-section of the tensile specimen is shown. The index of distribution was determined on the basis of particle count in elementary measuring fields. The regression equation describing the change of the considered index was found as a function of the pressure die casting parameters. The conclusion presents an analysis of the obtained results and their interpretation.