Formability of wire-arc deposited AISI 316L sheets for hybrid additive manufacturing applications

Abstract

This paper is focused on the formability of wire-arc additively manufactured AISI 316L stainless steel sheets with the purpose of analysing the feasibility of including this material in hybrid additive manufacturing chains involving sheet metal forming operations. Conventional tensile tests performed in specimens obtained from different orientations to the building direction were carried out to characterise the mechanical properties, the strain loading paths and the limiting strains at fracture. Microstructure observations combined with fractography analysis add insight to the results by establishing a link between the forming limits by fracture and the crack opening mechanisms. Results obtained for wrought commercial AISI 316L stainless steel sheets are included for comparison purposes and reveal that the additively manufactured sheets have a much stronger anisotropic behaviour and poorer formability due to their dendritic-based microstructure. Still, the forming limits obtained from the experiments allow concluding that the additively manufactured sheets can withstand large plastic deformations and, therefore, can be used in hybrid additive manufacturing routes.

Hybrid Manufacturing of Stiffening Grooves in Additive Deposited Thin Parts

“…Wrought commercial stainless-steel sheets are included for comparison purposes and the overall results show that the proposed analytical model can be successfully used to characterize plastic deformation and failure by the tearing in hybrid additive manufacturing of stiffening grooves. Microstructure observations and anisotropy justify the differences in the mechanical response of the additively deposited and wrought commercial stainless-steel sheets, in agreement with previous observations of the authors in the same material [14] and of other authors in different materials [15].…”

“…This type of texture is not visible in the corresponding specimen of the wrought commercial sheets and is attributed to the dendriticbased microstructure of the additively deposited sheets, which is made of columnar grains with primary arms aligned with the building direction and secondary arms bonding the neighboring grains together (Figure 6b). This type of microstructure, which was previously observed by the authors in tensile tests [14], is different from the equiaxial microstructure of the wrought commercial sheets and is the main reason behind the anisotropic behavior of the additively deposited sheets.…”

“…The formability limits of the additively deposited and wrought commercial AISI stainless-steel sheets were determined by combining the surface strains acquired by a ital image correlation (DIC) during tensile tests with measurements of the final thick of the cracked surfaces with a stereomicroscope to obtain the gauge length strains a fracture. The procedure is comprehensively explained in a previous paper publishe the authors [14], from where the fracture forming limits (FFLs) of the two types of sh that are shown in Figure 4 were retrieved. The formability limits of the additively deposited and wrought commercial AISI 316L stainless-steel sheets were determined by combining the surface strains acquired by a digital image correlation (DIC) during tensile tests with measurements of the final thickness of the cracked surfaces with a stereomicroscope to obtain the gauge length strains at the fracture.…”

“…The formability limits of the additively deposited and wrought commercial AISI 316L stainless-steel sheets were determined by combining the surface strains acquired by a digital image correlation (DIC) during tensile tests with measurements of the final thickness of the cracked surfaces with a stereomicroscope to obtain the gauge length strains at the fracture. The procedure is comprehensively explained in a previous paper published by the authors [14], from where the fracture forming limits (FFLs) of the two types of sheets that are shown in Figure 4 were retrieved.…”

“…Figure 4.Fracture forming limits of the additively deposited and wrought commercial AISI 316L stainless-steel sheets in principal strain space (data obtained from[14]). …”