The Microstructure and Mechanical Properties of the Ball-Milled Al-Mn-Zr Alloys with Ce and Y Additions

Mechanical alloying (MA), hot press sintering (HPS), and post-annealing were used to create high-performance Al-Mn-Zr-based quaternary alloys containing the rare earth (RE) elements Ce and Y. Three alloy compositions (Al-4Mn-1,2Zr, Al-4Mn-1,2Zr-0,6Y, and Al-4Mn-1,2Zr-0,6Ce (at.%)) were high energy ball milled for 10 h, consolidated at 350 °C or 450 °C and subsequently annealed at 350-450 °C for periods ranging from 15 minutes to 4 hours’ analysis of crystallite size supported the extensive grain refinement during milling (16--20 nm), whereas compaction at temperatures at 450 caused a notable grain coarsening (up to 84 nm. SEM-EDS elemental mapping revealed precipitation free zones and intermetallic-rich zones, indicating precipitates formation during thermal processing. After milling, Al solid solution and Al4Mn for Al-Mn-Zr and Al-Mn-Zr-Y alloys, Al6Mn phase for Al-Mn-Zr-Ce alloy were revealed. After sintering Al6Mn and Al3Zr phases precipitated for all alloys studied. According to the compression tests, the addition of Ce and Y to Al-Mn-Zr alloys varies in composition and heat treatment. Ce-containing alloys have high ultimate compression strength (UCS) and ductility, while Y-modified alloys balance strength and ductility. Annealing for 1-4 hours at 400°C gave maximum values for Al-4Mn-1,2Zr. The alloy also had maximum microhardness and macro-hardness after annealing (~430 HV and 370 HV) respectively. Annealing led to a rise in hardness for Ce and Y alloys from about (~ 250-280) HV to more than ~350 HV. Sintering pieces at 450 °C produced nearly the ideal density which shows an improved packing of the structure. Still, keeping the samples at 450°C for a long period following mild pressing caused the grains to become coarse and diminished the ability to restore their properties. High alloyed Al-Mn-Zr based alloys exhibited superior strength properties and Y/Ce increased ductility. It is shown in the study that the MA-HPS process can successfully design high-performance Al alloys and has implications for lightweight parts.