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

Abstract

This study investigated the impact of the equal channel angular pressing (ECAP) combined with heat treatments on the microstructure and mechanical properties of AlSi10Mg alloys fabricated via selective laser melting (SLM) and gravity casting. Special attention was directed towards determining the effect of post-fabrication heat treatments on the microstructural evolution of AlSi10Mg alloy fabricated using two different routes. Three initial alloy conditions were considered prior to ECAP deformation: (1) as-cast in solution treated (T4) condition, (2) SLM in T4 condition, (3) SLM subjected to low-temperature annealing. Light microscopy, transmission electron microscopy, X-ray diffraction line broadening analysis, and electron backscattered diffraction analysis were used to characterize the microstructures before and after ECAP. The results indicated that SLM followed by low-temperature annealing led to superior mechanical properties, relative to the two other conditions. Microscopic analyses revealed that the partial-cellular structure contributed to strong work hardening. This behavior enhanced the material’s strength because of the enhanced accumulation of geometrically necessary dislocations during ECAP deformation.

Microstructural Evolution, Hardness, and Strengthening Mechanisms in SLM AlSi10Mg Alloy Subjected to Equal-Channel Angular Pressing (ECAP)

“…Taking into account the strengthening components, the increases in strength in the sample after two passes of ECAP can be expressed as follows: σ y = 72 f riction stress + 79 Orowan + 81.6 Hall−Petch + 186.7 dislocation = 419.3 MPa (7) According to Equation ( 7), the calculated yield strength of the AlSi10Mg alloy subjected to two passes of ECAP was equal to 419.3 MPa. This estimated value of YS was similar to the experimental value of 382 MPa obtained from the static compression test in our previous study [25].…”

“…Meanwhile, it is only very recently that the microstructure and mechanical properties of SLM-fabricated and then ECAP-processed AlSi10Mg alloy were investigated by the current authors [25]. In this article, it was found that the yield strength increased significantly (up to 382 MPa).…”

“…As discussed in the Introduction section, such a cellular (heterogeneous) microstructure offered outstanding strain hardenability; however, their partial disintegration resulted in the decrement of the alloy hardness, which is discussed later. A more detailed analysis of the decomposition of the cellular substructure after low-temperature annealing was discussed in our previous article [25].…”

“…where β is a material constant (0.16), M is the Taylor factor (3.06) [30,31], G is the shear modulus (taken as 26 GPa), ρ d is the dislocation density 1.23 × 10 15 m −2 (the dislocation density was taken from the XRD results published in our previous article [25]), and b is the Burgers vector of the Al (~0.286 nm). However, in the case of additively manufactured alloys, the strength increment should be considered as a sum of statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs) which is given by the following equation:…”

Evolution of Microstructure, Texture and Corrosion Properties of Additively Manufactured AlSi10Mg Alloy Subjected to Equal Channel Angular Pressing (ECAP)

“…More details about the applied scanning strategy and SLM process parameters can be found in our previous studies [33,34].…”