Microstructure and Mechanical Properties Characteristics of 2319 Aluminum Alloy Fabricated Using Cold Metal Transfer Pulsed Advanced (CMT-PADV) Wire Arc Additive Manufacturing

This work examines the microstructure characteristics, evolution processes, and mechanical properties of wire arc additive manufactured specimens using cold metal transfer-pulse advanced (CMT-PADV). An arc extinguishing process occurs when the pulse cycle shifts to the cold metal transfer (CMT) cycle, resulting in a distinct microstructure known as "regularly distributed grain bands". Under thermal influence, the equiaxed dendrites in the upper region progressively transform into equiaxed grains with a random grain orientation. The microstructural precipitation process involves the sequential formation of G.P. zones (Guinier–Preston Zones), θ″ phases, θ′ phases, and θ phases. The initial three sub-stable phases introduce lattice distortion within the matrix, thereby enhancing the strengthening effects. Due to varying temperatures and thermal cycling, the sub-stable phase's composition changes, leading to a progressive increase in mechanical properties from the top to the bottom of the specimens. The ultimate tensile strength (UTS) of the thin wall gradually increased from 293.5 to 307.7 MPa, and the yield strength (YS) gradually increased from 127.4 to 134.2 MPa; the average elongation was recorded at 16%, with negligible variations. Furthermore, the alternating distribution of coarse and fine grains results in lower longitudinal properties compared to transverse properties. Specifically, the longitudinal UTS and YS decreased to 293.7 MPa and 123 MPa, respectively, while elongation reduced to 13.1%.

Graphical Abstract