Microstructure and mechanical properties of a TiB2-modified Al–Cu alloy processed by laser powder-bed fusion

P Mair,L Kaserer,J Braun,N Weinberger,I Letofsky-Papst,G Leichtfried

doi:10.1016/j.msea.2020.140209

P Mair, L Kaserer + Show 4 more

Open Access

https://doi.org/10.1016/j.msea.2020.140209

Copy DOI

Abstract

In this work, crack-free samples with a relative density of 99.5 ± 0.1% were produced from a gas-atomized Al–Cu–Ag–Mg–Ti–TiB2 powder via laser powder-bed fusion. The homogeneous equiaxed microstructure without preferred grain orientation shows the α-Al grains’ mean size to be 0.64 μm ± 0.26 μm TiB2 particles with sizes of several tens of nm up to 1.5 μm were observed in the as-built component. Small TiB2 particles of up to approx. 200 nm are located within the α-Al grains, which show a semi-coherent interface to the α-Al phase. Larger TiB2 particles of up to 1.5 μm accumulate in the liquid between the growing α-Al grains during solidification and inhibit grain growth. Al2Cu phase is precipitated at the α-Al grain boundaries. Coarse Al2Cu precipitates, which are slightly enriched with silver and magnesium, are also observed within the grains preferentially precipitated on small pores and TiB2 particles. The novel fine-grained microstructure results in the as-built state in a tensile strength of 401 ± 2 MPa and total elongation at fracture of 17.7 ± 0.8%.

Highlights

Laser powder-bed fusion (LPBF), the dominant technology in addi tive manufacturing (AM) for metallic materials, offers new opportunities for the structural optimization of lightweight components [1,2]
Scanning electron microscopy (SEM) images (Fig. 1a and b) show that the particles have several satellites and that some are slightly elliptical in shape
A205 was processed via LPBF with a relative density of 99.5 ± 0.1% and a crack-free microstructure

Summary

Introduction

Laser powder-bed fusion (LPBF), the dominant technology in addi tive manufacturing (AM) for metallic materials, offers new opportunities for the structural optimization of lightweight components [1,2] It may be regarded as a type of rapid solidification welding (cooling rate of ~103–106 ◦C/s [3]), which results in a unique, non-equilibrium micro structure. Several theories have been advanced with respect to the mechanism of grain refinement by TiB2 in Al-alloys, including the carbide-boride particle theory [14], the peritectic theory [15], the peritectic hulk theory [16], the hypernucleation theory [17], and the duplex nucleation theory [18]. Fan et al [12]

Methods

Results

Discussion

Conclusion