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Fatigue and dynamic aging behavior of a high strength Al-5024 alloy fabricated by laser powder bed fusion additive manufacturing.

Fatigue and dynamic aging behavior of a high strength Al-5024 alloy fabricated by laser powder bed fusion additive manufacturing.

Authors :
He, Peidong
Webster, Richard F.
Yakubov, Vladislav
Kong, Hui
Yang, Qin
Huang, Shuke
Ferry, Michael
Kruzic, Jamie J.
Li, Xiaopeng
Source :
Acta Materialia. Nov2021, Vol. 220, pN.PAG-N.PAG. 1p.
Publication Year :
2021

Abstract

A high strength Al-5024 alloy containing Sc and Zr with a bi-modal microstructure consisting of fine equiaxed and coarse columnar grains was successfully fabricated by laser powder bed fusion (LPBF) additive manufacturing. The formation of the bi-modal microstructure was mainly due to both the formation of primary Al 3 Sc precipitates that act as nucleation sites and the steep temperature gradient during LPBF. By simulating the thermal field of a single melt pool, the formation mechanism of the bi-modal microstructure was explained. It was found by simulation that a solidification interface velocity less than 110 mm/s was beneficial to the nucleation of Al 3 Sc precipitates and, hence, facilitated the formation of a fine grain microstructure. Applying different heat treatments revealed a trade-off trend between yield strength and ductility as a function of the heat treatment time, and a correlation in fatigue life and yield strength was observed, both of which were closely related to the status of the secondary Al 3 Sc precipitates. The highest ultimate tensile strength of 450 MPa and corresponding 107 cycle fatigue strength of 105 MPa were achieved after hot isostatic pressing for 4 h at 325 °C with 100 MPa pressure. Dynamic strain aging was found to occur in both as-built and some heat treated samples, which was related to magnesium (Mg) solute atom clustering attributed to: (i) the formation of a diffuse "Mg wall" due to the repetitive melting and rapid cooling in LPBF, and (ii) the growth of intragranular (Al 3 Sc) and intergranular precipitates (Fe-, Mn-rich) during subsequent heat treatment, thereby leading to an increasing number of misfit dislocations that promote the formation of Mg atom clusters. [Display omitted] [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
13596454
Volume :
220
Database :
Academic Search Index
Journal :
Acta Materialia
Publication Type :
Academic Journal
Accession number :
153433418
Full Text :
https://doi.org/10.1016/j.actamat.2021.117312