Microstructural evolution and strengthening mechanism of an Al–Si–Mg alloy processed by high-pressure torsion with different heat treatments

Laser powder bed fusion (L-PBF) is an additive manufacturing technology that is gaining increasing interest in aerospace, automotive and biomedical applications due to the possibility of processing lightweight alloys such as AlSi10Mg and Ti6Al4V. Both these alloys have microstructures and mechanical properties that are strictly related to the type of heat treatment applied after the L-PBF process. The present review aimed to summarize the state of the art in terms of the microstructural morphology and consequent mechanical performance of these materials after different heat treatments. While optimization of the post-process heat treatment is key to obtaining excellent mechanical properties, the first requirement is to manufacture high quality and fully dense samples. Therefore, effects induced by the L-PBF process parameters and build platform temperatures were also summarized. In addition, effects induced by stress relief, annealing, solution, artificial and direct aging, hot isostatic pressing, and mixed heat treatments were reviewed for AlSi10Mg and Ti6AlV samples, highlighting variations in microstructure and corrosion resistance and consequent fracture mechanisms.

“…Thus, the high mechanical properties can be expressed through the following sum of strengthening effects [ 182 , 183 ]:

where

(MPa) is the friction stress of the lattice,

(MPa) is the solid solution strengthening,

(MPa) is the strength obtained by the grain size (Hall–Petch equation),

(MPa) is the Orowan strengthening,

(MPa) is the dislocation hardening and

Section: L-pbfed Alsi10mg: Mechanical Propertiesmentioning

confidence: 99%

“…Hadadzadeh et al [ 182 ] proposed the use of the Hall–Petch equation (considering the cellular structure of the L-PBFed AlSi10Mg):

where

is a material constant (~0.04 MPa m 1/2 , [ 184 ]), and

is the average cell size (m). The Orowan strengthening was expressed by Dieter [ 185 ], as follows:

where

(GPa) is the Al shear modulus (26.5, [ 158 , 183 ]),

is the Burgers vector (0.286 nm), [ 158 , 184 ],

is the interparticle spacing (nm)

[ 148 ], and

is the particle radius (nm). Figure 25 a,b show the schematic interaction between a dislocation and the cell boundaries via Orowan looping in a full-cellular AlSi10Mg structure [ 164 ].…”

Section: L-pbfed Alsi10mg: Mechanical Propertiesmentioning

confidence: 99%

Additive Manufacturing of AlSi10Mg and Ti6Al4V Lightweight Alloys via Laser Powder Bed Fusion: A Review of Heat Treatments Effects

Ghio

Cerri

2022

“…As widely reported in the literature, the strengthening mechanisms of AlSi10Mg samples change before and after the various heat treatments affecting the mechanical properties, as previously discussed. This behavior is described by all contributions of the following equation [65,66]:…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Work Hardening of Heat-Treated AlSi10Mg Alloy Manufactured by Selective Laser Melting: Effects of Layer Thickness and Hatch Spacing

Ghio

Cerri

2021

The present study analyzed the microstructure and the mechanical properties of AlSi10Mg SLMed bars (10 × 10 × 300 mm) and billets (10 × 100 × 300 mm) before and after the direct aging at 200 °C for 4 h and the T6 heat treatment. The discussed results are compared to those obtained by the AlSi10Mg samples manufactured with the same geometry but using different process parameters (layer thickness higher than 40 μm and a hatch spacing lower than 100 μm) and also through the Quality Index (QI). These work conditions allow the obtaining of a microstructural variation and different tensile properties in as-built top samples. In both batches, the cycle time was 45 h and together with the preheated build platform at 150 °C, induced an increase of UTS (Ultimate Tensile Strength) and yield strength on the bottom rather than the top samples due to the aging phenomena. Upon completion of the direct aging heat treatment, the effects induced by the platform were cancelled, keeping a full cellular microstructure that characterized the as-built SLMed (Selective Laser Melted) samples. Moreover, the Considère criterion and the work hardening analysis showed that the failure occurs after the necking formation in some of the T6 heat-treated samples. In this last case, the Si eutectic network globularized into Si particles, causing a decrease of UTS (from around 400 MPa to 290 MPa) in favour of an increase of ductility up to 15% and reaching a QI in the range 400 ÷ 450 MPa. These values place these samples between the high-quality aluminium cast alloy and T6 heat-treated ones.

“…The chemical modification and heat treatment methods are constrained by economy, resources, and environment. In recent years, high-pressure torsion, hot rolling, equal channel angular pressing and semi-solid die casting, have been employed to obtain the ideal microstructures of Al-Si alloys [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. Huang et al [ 26 ] found that hot deformation could not only effectively eliminate casting defects, but also make the distribution of eutectic Si particles of Al-Si alloy even.…”

Section: Introductionmentioning

confidence: 99%

Influence of Modification on Flow Stress Behavior and Corrosive Properties of a Hypoeutectic Al-Si Alloy

Song

Huang³

et al. 2022

The flow stress behavior and corrosive properties of Al-7Si alloy were studied by thermal compression test, electrochemical test, and electron probe microanalysis. The influences of temperatures, strain rates, strains, and morphology of Si particles on stress-strain curves of Al-7Si alloy were analyzed. The peak stress of unmodified-Al-7Si alloy is higher than that of Sr-modified-Al-7Si alloy at the same deformation conditions, and the phenomenon is obviously relevant to the distribution and morphology of Si particles. The morphology of Si particles of unmodified-undeformed-Al-7Si alloy is a typical thick layer, and that of unmodified-deformed-Al-7Si alloy is broken into relatively small particles and the distribution is relatively even in homogeneous deformation zone II. The distribution of Si particles in Sr-modified-deformed-Al-7Si alloy is obviously more even than undeformed alloy. The effect of a small deformation of 20% on the distribution and morphology of Si particles is obviously smaller than that of a large deformation of 50%. The electrochemical self-corrosion potential of Sr-modified-Al-7Si alloy is higher than that of unmodified-Al-7Si alloy, and it proves that the distribution and morphology of Si particles have a certain influence on the corrosive properties of Al-7Si alloy. That is, the even fine Si particles are more conducive to improving the corrosive properties of Al-7Si alloy.