Effect of Solution Treatment on Recrystallization,Texture and Mechanical Properties of 7A65-T74 Aluminum Alloy Super-thick Hot Rolled Plate

The effects of the solution treatment on the microstructure,recrystallization,texture composition and properties of 7A65-T7451(120 mm)hot rolled plates at H/2(1/2 thickness)and H/4(1/4 thickness)were studied.The results show that the hot rolled microstructure mainly contains a large amount of MgZn_(2) phases and minor Al_(7)Cu_(2)Fe phase.After solid solution treatments,a large amount of MgZn_(2) phases are dissolved back into the aluminum matrix.The main texture types at H/4 are R-Cube,Cube and part of Brass texture,and the main texture types at H/2 are Cube,R,and Copper texture.The qualitative analysis by Schmidt's law reveals that Copper texture at H/2 will deepen the anisotropy of plate metal properties.For the plate with the same thickness,the two-stage solution state has better mechanical properties due to the lower degree of recrystallization and stronger grain boundary strengthening effects.Under the two-stage solution system of 460℃/165 min+477℃/165 min,the composite mechanical properties of the alloy plate at H/4 are the best and the anisotropy is not obvious.The tensile strength,yield strength,and elongation along the rolling direction are 561.9 MPa,523.4 MPa,and 10.6%,respectively..

Improvement of microstructure and mechanical properties of Al−Cu−Li−Mg−Zn alloys through water-cooling centrifugal casting technique

The microstructure and mechanical properties of as-cast Al−Cu−Li−Mg−Zn alloys fabricated by conventional gravity casting and centrifugal casting techniques combined with rapid solidification were investigated.Experimental results demonstrated that compared with the gravity casting technique,the water-cooling centrifugal casting technique significantly reduces porosity,refinesα(Al)grains and secondary phases,modifies the morphology of secondary phases,and mitigates both macro-and micro-segregation.These improvements arise from the synergistic effects of the vigorous backflow,centrifugal field,vibration and rapid solidification.Porosity and coarse plate-like Al13Fe4/Al7Cu2Fe phase result in the fracture before the gravity-cast alloy reaches the yield point.The centrifugal-cast alloy,however,exhibits an ultra-high yield strength of 292.0 MPa and a moderate elongation of 6.1%.This high yield strength is attributed to solid solution strengthening(SSS)of 225.3 MPa,and grain boundary strengthening(GBS)of 35.7 MPa.Li contributes the most to SSS with a scaling factor of 7.9 MPa·wt.%^(-1).The elongation of the centrifugal-cast alloy can be effectively enhanced by reducing the porosity and segregation behavior,refining the microstructure and changing the morphology of secondary phases.

Microstructure and rheological properties of a semisolid A356 alloy with erbium addition

The effects of erbium addition on the rheological properties and microstructure of a semisolid A356 alloy were studied.The semisolid slurries were prepared through the serpentine channel technique before they were thixoformed using parallel-plate compre ssion with cylindrical discs.The grain and globule size decreases as the Er content increases,resulting in an improved and uniform distribution of spherical primaryα-Al phase within the semisolid slurry.The addition of the Er modifies the grain morphology and size of theα-Al grains,resulting in a better and more uniform distribution of spherical primaryα-AI phase within the semisolid slurry.As a result,rheocast quality index increases with the addition of Er,which is suitable for the thixoforming process.The A356 alloy without Er has the highest viscosity herein.The viscosity decreases,and the flow characteristics of the semisolid feedstock are expected to improve when Er is added as a result of the refinement of primary a-Al and modification of eutectic silicon.Furthermore,the refined semisolid A356 alloys with Er show a slightly larger fraction of highangle grain boundaries compared to that for the unrefined alloy.