https://research.birmingham.ac.uk/portal/files/19592544/NR_mod_CL31_12_9_14_F4.pdf

Selective laser melting of AlSi10Mg alloy: Process optimisation and mechanical properties development

The aluminum alloys of the 6xxx series contain an excess of Si above that required to form stoichiometric Mg 2 Si, which is added to improve the age hardening due mostly to precipitation of metastable β″ precipitates. The excess Si is not believed to alter the precipitation sequence, structure and lattice parameters of the different metastable precursors, but rather promotes formation of additional particles/phases which do not contribute to hardening significantly. The presence of excess Si changes the composition and density of metastable β″ particles, although a systematic study of the Mg/Si ratio in particles from alloys of different composition is lacking. In this paper, it is shown that the precipitation sequence in the balanced alloy is independent of the composition and the strength increases with Mg 2 Si level. This is due primarily to both a higher volume fraction and a refined distribution of the β″ particles. Excess Si increases the effective amount of the hardening phases above ∼0.9 wt.% Si. It modifies the Mg/Si ratio in the clusters/zones and β″ precipitates and improves strength by altering their size, number density and distribution. In addition, the extent and rate of strengthening increases until the overall Mg to Si ratio in the alloy is close to approximately 0.4. The hardening precipitates with reduced Mg to Si ratio become less stable with aging and cause a decrease in strength during over aging.

Precipitation hardening in Al–Mg–Si alloys with and without excess Si

Influence of heat treatment on the microstructure and mechanical properties of 6005 and 6082 aluminium alloys

Quantification and characterisation of porosity in selectively laser melted Al–Si10–Mg using X-ray computed tomography

https://hal.archives-ouvertes.fr/hal-00664802/document

Integrated modeling of friction stir welding of 6xxx series Al alloys: Process, microstructure and properties

Aluminum alloys containing Mg and Si as the major solutes are strengthened by precipitation of the metastable precursors of the equilibrium β (Mg2Si) phase in one or more sequences. There are several metastable particles that can form during ageing, but the strengthening potential of these particles relative to one another is not extensively studied. In this paper, the precipitation and hardening potential of different metastable precursors in an Al–0.4%Mg–1.3%Si–0.25%Fe (wt.%) alloy is studied with the help of differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and hardness measurements. It has been found that the hardness increase in a freshly solutionized alloy during natural ageing occurs primarily due to precipitation of clusters and zones, while peak hardness is achieved due to precipitation of β” particles. The particles formed following β” phase are not effective hardeners.

A.K. Gupta

Papers

Precipitation hardening in Al–Mg–Si alloys with and without excess Si

Precipitation hardening processes in an Al–0.4%Mg–1.3%Si–0.25%Fe aluminum alloy