Repurposing the θ (Al2Cu) phase to simultaneously increase the strength and ductility of an additively manufactured Al–Cu alloy

Xiaohua Hu, Sumit Bahl, Amit Shyam, Alex Plotkowski, Brian Milligan, Lawrence Allard, James A. Haynes, Yang Ren, Andrew Chuang

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

The Al–Cu–Mn–Zr (ACMZ) cast family of alloys offers unique properties and value propositions for higher strength, higher temperature lightweight components of future vehicles. Previous research has demonstrated trade-offs in the selection of the alloy chemistry in which an increase in Cu content from 6 up to 9 wt% improves hot tear resistance but lowers ductility. However, a recent study has demonstrated that higher-Cu (9Cu) ACMZ fabricated with laser powder bed fusion additive manufacturing (AM) results in an increase in both ductility and strength when compared to as-aged microstructure of cast 9Cu alloys. The mechanisms of differing mechanical performance of the cast and AM ACMZ alloys are elucidated in the current paper through the utilization of in situ high energy x-ray diffraction (HEXRD) tensile testing wherein lattice strains of different phases are calculated and correlated to their stresses. The ACMZ alloys consisted of theta (θ) and theta prime (θ) phases (both Al2Cu in nominal composition) within an aluminum matrix. The larger micron-size θ phase which decorated the grain boundaries in 9Cu ACMZ cast alloys recorded small lattice strains, while the submicron, homogeneously distributed θ phase in the 9Cu ACMZ AM alloy recorded considerably higher lattice strains. The maximum stress reached in the θ phase for the cast 9Cu alloy was found to be ∼280 MPa, which was lower than the AM 9Cu alloy which registered a maximum stress of ∼1.4 GPa. These measurements indicate that delayed fracture of the finer intermetallic phases simultaneously improves the ductility and strength of AM 9Cu alloy relative to the cast 9Cu alloy, which exhibits early fracture of the larger intermetallic particles.

Original languageEnglish
Article number143511
JournalMaterials Science and Engineering: A
Volume850
DOIs
StatePublished - Aug 11 2022

Funding

Oak Ridge National Laboratory is operated by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. This research used resources of the Advanced Photon Source (APS), a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357 . This research sponsored by Powertrain Materials Core Program, under the Propulsion Materials Program (managed by Jerry Gibbs), Vehicle Technologies Office , U.S. Department of Energy.

Keywords

  • Additive manufacturing
  • Aluminum alloys
  • HEXRD

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