Unique microstructure evolution of a novel Ti-modified Al-Cu alloy processed using laser powder bed fusion

Philipp Mair*, Jakob Braun, Lukas Kaserer, Lukas March, David Schimbäck, Ilse Letofsky-Papst, Gerhard Leichtfried

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Numerous studies on laser powder bed fusion (LPBF) have already demonstrated the evolution of out-of-equilibrium microstructures with metastable phases. In the present work, a self-designed, pre-alloyed Al-Cu-Ti-Ag-Mg alloy is processed using LPBF. The solidification path, which is necessary to achieve sufficient supercooling to exceed the critical nucleation supercooling (ΔTn) required for heterogeneous nucleation on L12 Al3Ti nuclei, is derived from the microstructure. This unique microstructure can be divided into two areas: Area 1, with a thickness in the building direction of 5–10 µm, solidifies first and forms on the bottom of the semicircular melting pool. It is dominated by columnar α-Al grains, which contain numerous precipitated cube-shaped Al-Cu-Ti-Ag nanoparticles. During the solidification of Area 1, the constitutional supercooling (ΔTCS) and the thermal supercooling (ΔTtherm) gradually increase. The Ti and Al atoms in the residual melt react to form numerous primary L12 Al3Ti particles, which are activated for heterogeneous nucleation and serve as nuclei for α-Al grain growth once ΔTtotal (ΔTCS + ΔTtherm) exceeds ΔTn. Area 2, formed by heterogeneous grain refinement, occupies the remaining part of the melting pool and consists of fine equiaxed α-Al grains. The cube-shaped Al-Cu-Ti-Ag nanoparticles precipitated from the supersaturated α-Al in Area 1 cannot be observed in Area 2. The novel alloy with a fine-grained microstructure exhibits a tensile strength of 475 ± 7 MPa in combination with an elongation to fracture of 8.7 ± 0.5%.

Original languageEnglish
Article number103353
JournalMaterials Today Communications
Volume31
DOIs
Publication statusPublished - Jun 2022

Keywords

  • Additive manufacturing
  • AlTi
  • Alloy design
  • Aluminum
  • Grain refinement
  • Laser powder bed fusion
  • Selective laser melting

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Materials Chemistry

Fields of Expertise

  • Advanced Materials Science

Treatment code (Nähere Zuordnung)

  • Basic - Fundamental (Grundlagenforschung)

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