Mechanical Properties Of Cold-Rolled Commercial Purity Aluminum And Its Annealing Dependence

Commercial purity aluminum has properties such as low density, easyfor processing, rich in minerals and low cost, which makes it wideapplications as a structural material. Suitable strengthening for improvingthe strength of commercial purity aluminum is the key to its application.Sever plastic deformation is one commonly used technology to improvethe strength of metallic materials. Annealing after plastic deformation is analternative way to control the mechanical properties of metallic materials.Therefore, to discover a feasible processing for commercial purityaluminum is of practical significance.In this paper, the impact of cold rolling on the mechanical propertiesof commercial purity aluminum, as well as changes in mechanicalproperties after traditional or electric pulse annealing was studied. Firstly,concepts of sever plastic deformation in metallic materials and hardeningby annealing were presented, as theoretical fundaments in strengtheningtechnology exploration and selection for industrial pure aluminum.Secondly, commercial purity aluminum was severely plastic deformedby means of cold rolling to various strains. Yield strengths of samples withdifferent strains were compared, with additional transmission electronmicroscopy characterization. A softening by further deformationphenomenon was discovered, resulted from the equiaxial structure withhigher density of dislocation and low angle grain boundaries in the samplewith lower strain. Theoretical calculation of the contribution of both grainboundaries and dislocations to yield strength was conducted, furthersupporting experimental observations. Thirdly, cold-rolled commercial purity aluminum with differentstrengths was annealed with electric furnace or oil bath in the sameconditions, and their changes in strength were compared. It was found thatwith the increase of yield strengths of cold-rolled materials, there existedthree regions:(i) hardening by annealing,(ii) no influence, and (iii)softening by annealing. Such phenomena could be explained by theprinciples of internal dislocations in ultrafine grains during the annealingprocess.Finally, cold-rolled commercial purity aluminum was annealed underelectric pulse, and mechanical properties of the materials were comparedwith those after conventional annealing. It was disclosed thathardening/softening trend by annealing was the same in conventional andelectrical pulse annealing, while the later was more effective. Higherefficiency in dislocations recovery and grain coarsening could be achievedby electrical pulse annealing, indicating worth explorations for the newtechnology.