The development of more environmentally friendly Al alloys reinforced with QC phase was supported by the Slovenian Research Agency (ARRS). The search for the best QC alloy systems was carried out within bilateral projects (between Slovenia and the United States of America in 2012/2013 and twice between Slovenia and Montenegro in 2012/2013 and 2014/2015) and postgraduate research grants (Young Researchers).
The Al-Mn-Si-Cu-Mg system showed the best results. The obtained compressive strength ranged from 625 to 785 MPa, the compressive yield strength from 315 to 430 MPa, and the compressive fracture strain from 5.2 to 21.5%, while the content of the primary QC phase ranged from 5 to 25%. Considering that the compressive yield strength of die casting alloys is slightly higher than the tensile yield strength, it is easy to conclude that the substitution of the conventional DIN 226 Al alloy (with a tensile strength of 240 MPa, tensile yield strength of 140 MPa and an elongation of 1%) by the QC alloy requires 50% less material to obtain the same functionality. To move from laboratory experiments to the industrial environment, researchers from the University of Ljubljana (UL), together with the staff of Iskra ISD, have already carried out three industrial high pressure die casting (HPDC) of the QC alloy. Prototype parts made from a new alloy were evaluated and analysed. In these castings, the mechanical properties were about 30% higher than those of the DIN 226 Al alloy. Some improvements were noted due to the higher liquidus temperature and the formation of the QC phase, which is crucial for enhancing the mechanical and physical properties. It is safe to say that the QC alloy has reached TRL 6 (Fig. 1 – Laboratory and HPDC microstructure of the QC alloy).
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Currently, the UL and Iskra ISD researchers are working on a PCT patent application for the chemical composition of the QC alloy to be filed in 2022. Due to the higher mechanical properties achieved in the laboratory and in industry, a direct contribution to solving the raw material problem is addressed. Further weight reduction of vehicles can accelerate the transition to low-emission mobility. To increase user acceptance of electric vehicles, weight reduction will lower the required battery capacity and thus the price of electric vehicles while increasing their range. Lighter vehicles are also important for customers as they are more efficient regardless of road conditions, improve road safety through shorter braking distances, and reduce impact energy in the event of a collision. As a fully recyclable material, QC alloy is key to achieving the broader goals of the circular economy and climate change agendas. Results of the project have already been presented as part of the EIT RM Jumpstarter competition in 2020 and the EIT RM Accelerator programme in 2021. It is expected that the QC alloy will be optimised and brought to market during the CastQC project.