Effect of sample orientation on the microstructure and microhardness of additively manufactured AlSi10Mg processed by high-pressure torsion

Abstract

For the first time, high-pressure torsion (HPT) was applied to additively manufactured AlSi10Mg built in two directions (vertical and horizontal) by selective laser melting (SLM), and the influence of extreme torsional strain on the porosity, microstructure and microhardness of the alloy was investigated. ImageJ analysis indicates that significant porosity reduction is achieved by 1/4 HPT revolution (low strain). Optical microscopy (OM) and scanning electron microscopy (SEM) observations reveal the steady distortion and elongation of the melt pools, the continuous elongation of the cellular-dendritic Al matrix and breakage of the eutectic Si phase network with increased HPT revolutions. Microhardness measurements indicate that despite the significant increase in hardness attained from HPT processing, hardness saturation and microstructural homogeneity are not achieved even after 10 HPT revolutions. X-ray diffraction (XRD) line broadening analysis demonstrates increased dislocation densities with increased HPT revolutions, which contributes to the considerably higher hardness values compared to as-received samples.

Effects of equal channel angular pressing and heat treatments on the microstructures and mechanical properties of selective laser melted and cast AlSi10Mg alloys

“…Additionally, considering strain gradient plasticity theory [34], a higher density of GNDs can accumulate near Al/Si interfaces in the S2 sample [35] during the severe plastic deformation, which increases strain hardening and improves mechanical properties [36]. The calculated dislocation density for the S2-2 sample (1.23 × 10 15 m -2 ) was slightly lower than the recently reported dislocation density (5.11 × 10 14 m -2 ) for the SLM AlSi10Mg alloy subjected to high-pressure torsion [10]. The values obtained from XRD analysis for the solution-treated, ECAP-processed samples were very close to the value reported by Cardoso et al [37] for as-cast Al-10wt.%Si (4.5 × 10 14 m -2 ), and by Zribi et al [38] for as-cast Al-7wt.%Si after ECAP (1.9 × 10 14 m -2 ).…”

“…(1), which demonstrates that the metal yield strength (σ y ) increases with decreasing grain sizes (d), i.e., "smaller is stronger". In this context, Yusuf et al [10] studied the effect of high-pressure torsion on the microstructural evolution and strength of SLM AlSi10Mg aluminum alloy and 316L steel. The results indicated a significant improvement in the hardness of the AlSi10Mg alloy (from 140 to 220 HV) and 316L steel (from ~ 240 to ~ 600 HV) which the authors of the following article [11] explained based on the extreme grain refinement and high dislocation densities originating from the unique heterogeneous microstructure.…”

Case Study of the Tensile Fracture Investigation of Additive Manufactured Austenitic Stainless Steels Treated at Cryogenic Conditions

“…Additive manufacturing (AM) technologies are currently considered to be a very promising solution to overcome such challenges, representing a quasi-pristine field of research for both metallurgists and process engineers. AM processes are a stimulating innovation, mainly in component design, enabling the manufacture of components not feasible via traditional methods [1,2].…”

“…The laser powder bed fusion process (LPBF), also known as selective laser melting (SLM), directly produces homogenous metal objects, layer by layer, from 3D Computer Assisted Drawing (CAD) data, by selectively melting fine layers of metal powder with a laser beam [1][2][3][4][5][6][7][8]. A considerable amount of material can be saved by designing properly for additive manufacturing with no loss in terms of mechanical properties [11][12][13].…”

“…Especially, in AM products, cryogenic treatment is still very rare. The austenitic 316L grade is a popular steel for cryogenics as demonstrated by the vast literature, with special applications in the field of liquid gas confinement and storage [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Mechanisms governing tensile properties at cryogenic temperatures for wrought materials have been extensively and deeply investigated [ 25 ].…”