Semisolid Alloys Processing in Functional Die

• Grant number: 24/06996-5
• Support Opportunities: Regular Research Grants
• Start date: April 01, 2025
• End date: March 31, 2028
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Principal Investigator: Eugênio José Zoqui
• Grantee: Eugênio José Zoqui
• Host Institution: Faculdade de Engenharia Mecânica (FEM). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Pressure die casting is the most used process for producing structural parts for the metalworking sector. It uses alloys with a eutectic composition and high iron content, generating parts with good mechanical properties but relatively high porosity and shrinkage voids, between 2 and 5%. Processing in the semisolid state (SSM) reduces the number of defects to less than 1% by practically eliminating porosity, also allowing the use of metallic alloys with low iron content, which generally have better mechanical, thermal, and electrical properties. Rheocasting and thixoforming processes stand out, as they compete with casting and forging. Alloys of the Al-Si and Mg-Al systems are commercially processed. For Al-Si alloys, SSM processing is carried out by injecting, under pressure, a mixture composed of solid Al-alpha particles immersed in liquid. This liquid generally has a composition close to the Al-Si eutectic. These solids immersed in the liquid give the mass high viscosity, generating laminar, non-turbulent flows during die filling, eliminating porosity but not contraction microvoids. Including the functionality in the injection dies, conventional or SSM aims to solve this problem. Explained: this involves the manufacture of injection matrices with mechanical actuators that consolidate solidification in its last stage when the material is practically solid (fs > 98 %). It should be remembered that shrinkage voids appear in the final 2 % of solidification. In this way, there is a combination of SSM technology, reducing porosity and introducing the concept of functionality in injection, reducing contraction microvoids. To this end, conventional foundry alloys (380/384), traditional SSM alloys (357, 319) and the new alloys developed and under development Al-Si-(Cu-Mg-Zn) and Al-Ti-(Cu-Mg-Zn-Si) will be tested. Two methods of preparing the semisolid slurry were chosen: GISS (Gas Induced Semi-Solid), in the case of Al-Si-(Cu-Mg-Zn) alloys and chemical modification, for Al-Ti-(Cu- Mg-Zn). The best production strategy is sought from the perspective of microstructure, the number of defects, the physical and mechanical properties of interest, energy expenditure and the sustainability of the process for the national industry. (AU)