Grain refinement and mechanical properties of pure aluminum processed by accumulative extrusion bonding

Ultrafine-grained aluminum processed by a new severe plastic deformation technique, accumulative extrusion bonding (AEB), was investigated. Microstructural characterization indicated good interfacial bonding and an average grain size of ~440 nm was obtained after six passes. Tensile testing revealed that the strength reached the maximum value of 195 MPa and the total elongation exceeded 16% after five passes. The hardness was also significantly improved and almost reached saturation after the first pass. SEM fractography of AEB-processed specimens after tensile test showed that failure mode was shear ductile fracture with elongated shallow dimples. Comparison with conventional accumulative roll bonding indicates that this new AEB technique is more effective in refining grain and improving mechanical properties of the specimens.

Effects of Ni content on microstructure and properties of aged Cu−0.4Be alloy

The effects of Ni content(0−2.10 wt.%)on the precipitated phase,strength and electrical conductivity of Cu−0.4wt.%Be alloy were investigated,and the influencing mechanism was analyzed.The results showed that the addition of Ni promoted the precipitation of strengthening phase in the alloy and remarkably enhanced the strengthening effect.When the Ni content was increased from 0 to 2.10 wt.%,the strength of the aged alloy initially increased and then decreased,and approached the maximum when the Ni content was 1.50 wt.%.The peak-aging parameters of the alloy containing 1.50 wt.%Ni were the aging temperature of 400℃ and the aging time of 60 min,where the tensile strength and yield strength of the aged alloy were 611 and 565 MPa,respectively,which were 2.8 times and 6.1 times those of the alloy without Ni.The electrical conductivity of the alloy with Ni increased with the aging time,and decreased with the increase of Ni content.With an increase of the aging time at 400℃,phase transition sequence of the Cu−0.4Be−1.5Ni alloy wasγ″phase→γ′phase→γphase.For the aging time of 60 min,a large number of dispersed nano-scale coherentγ″phase andγ′phase formed in the alloy with a remarkable strengthening effect,which was mainly responsible for the high strength of the alloy.

Effect of Cu on microstructure,mechanical properties,and texture evolution of ZK60 alloy fabricated by hot extrusion−shearing process

As-cast Mg-6Zn-xCu-0.6Zr(x=0,0.5,1.0,wt.%)alloys were fabricated by permanent mold casting;then,the alloys were subjected to homogenization heat treatment and extrusion-shearing(ES)process.The microstructure and mechanical properties of the alloys were evaluated by OM,SEM/EDS,XRD,TEM,EBSD and tensile tests.The results show that the hard MgZnCu phase in Cu-added alloy can strengthen particle-stimulated nucleation(PSN)effect and hinder the migration of dynamic recrystallization(DRX)grain boundary at an elevated temperature during ES.The ZK60+0.5Cu alloy shows an optimal tensile strength–ductility combination(UTS of 396 MPa,YS of 313 MPa,andδ=20.3%)owing to strong grain boundary strengthening and improvement of Schmid factor for{0001}■basal slip.The aggregation of microvoids around the MgZnCu phase mainly accounts for the lower tensile elongation of ZK60+1.0Cu alloy compared with ZK60 alloy.

Effect of cold rolling deformation on microstructure evolution and mechanical properties of spray formed Al−Zn−Mg−Cu−Cr alloys

The impact of cold rolling deformation,which was introduced after solid solution and before aging treatment,on microstructure evolution and mechanical properties of the as-extruded spray formed Al−9.8Zn−2.3Mg−1.73Cu−0.13Cr(wt.%)alloy,was investigated.SEM,TEM,and EBSD were used to analyze the microstructures,and tensile tests were conducted to assess mechanical properties.The results indicate that the D1-T6 sample,subjected to 25%cold rolling deformation,exhibits finer grains(3.35μm)compared to the D0-T6 sample(grain size of 4.23μm)without cold rolling.Cold rolling refines the grains that grow in solution treatment.Due to the combined effects of finer and more dispersed precipitates,higher dislocation density and smaller grains,the yield strength and ultimate tensile strength of the D1-T6 sample can reach 663 and 737 MPa,respectively.In comparison to the as-extruded and D0-T6 samples,the yield strength of the D1-T6 sample increases by 415 and 92 MPa,respectively.