Microstructures and tensile properties of an A1-12 wt pct Si alloy produced by reciprocating extrusion

Abstract

A reciprocating extrusion (RE) process has been developed for producing A1-12 wt pct Si bulk alloys with fine and uniform microstructures and superior properties. Two starting forms were used: disks produced by the hammer-and-anvil method and cast billets produced by casting. Variations of microstructure and mechanical properties with the number of extrusion passes are investigated for these two starting forms. The results show that the porosity along the interfaces between the rapidly solidified layers could be completely eliminated to give a sound matrix. The Si-phase particles in both cases could be refined and distributed uniformly. The strength and ductility of all specimens are also enhanced, until the microstructure reaches an optimum state, as the number of extrusion passes increases. The tensile properties of the rapidly solidified Al-Si alloys are found to be superior to those of ingot-processed alloys, due to the inherent finer particles produced by rapid solidification. The mechanism for the improvement of the microstructures and properties is also discussed.

Microstructure evolution in magnesium alloy AZ31 during cyclic extrusion compression

“…On the other hand, previous studies on materials such as pure Al [6,7], Al alloys [8,9], Mg-15Al-1Zn [10], Pb-50 vol.% Sn alloys [11] revealed that CEC can refine grains, second phase structures and inclusions. Regarding the refining mechanism, Yeh et al [10,12,13] proposed that particle fragmentation, dynamic recrystallization and repeated mass flow during deformation refine the grains and inclusions. Richert et al [7] suggested that the microstructure evolves from a cell block structure at lower strains into an equiaxed cell and subgrain structure assisted by localized glide and shear at higher strains.…”

Microstructural refinement and homogenization of Mg–SiC nanocomposites by cyclic extrusion compression

“…Due to its unique shear deformation mode and extremely high accumulated strains, SPD of metal matrix composites is particularly attractive. After light metal matrix composites, such as Al-Si and Mg-Al-Mg 2 Si, were processed by cyclic extrusion compression (CEC), the Si or Mg 2 Si phases were refined and distributed uniformly in the matrix [19][20][21]. Therefore, it is anticipated that the SPD process may be a good candidate for producing nanocomposites with a homogeneous dispersion of nanoparticles.…”

Investigation on effects of reciprocating extrusion process on microstructure of AA 6061 based composites

“…This was attributable to the fine, uniform silicon particle distribution, which not only resulted in a dispersion hardening effect but also raised the elongation and fracture strain. 9 Reciprocating extrusion is a novel method to refine the grains and inclusions of 7075 Al alloy. Reciprocatingly extruded 7075-T6 alloys exhibit superior strength-toughness combinations to conventional 7000 series alloys.…”

“…In comparison with the ingot processed Al–12 wt-Si alloy, the layer deposited alloy exhibited superior mechanical properties. This was attributable to the fine, uniform silicon particle distribution, which not only resulted in a dispersion hardening effect but also raised the elongation and fracture strain 9. Reciprocating extrusion is a novel method to refine the grains and inclusions of 7075 Al alloy.…”