Investigation On Processing Microstructure And Mechanical Properties Of Al-Zn-Mg-Cu Aluminum Alloy By High Pressure Torsion

The second phase particles dispersed in nanoscale size aluminum alloy material aresuccessfully prepared via using severe plastic deformation (SPD) of Al-Zn-Mg-Cu alloy(high strength aluminum alloy7075) experiment in high pressure torsion(HPT).Microstructure of nanoscale size bulk aluminum alloy material was characterizedusing metal ographic microscope (OM), X-ray diffraction (XRD), scanning electronmicroscopy (SEM) and transmission electron microscopy (TEM). Microstructuralevolution during high pressure torsion of block coarse grained material was analyzed anddiscussed in detail based on microstructural studies. Mechnical properties of nanoscalesize bulk coarse grained Al-Zn-Mg-Cu alloy, such as microhardness and tensile properties,were measured and studied in terms of microstructure and fracture morphology.Block7075of the initial condition were characterized using OM. It is shown thatthese sample are coarse grains crystals with equal geometry and the average grains size is600um. Al-Zn-Mg-Cu alloy of different heat treatment the initial state are prepared usingthe SPD technology by high pressure torsion (room temperature).This experiment underthe condition of high pressure to reverse the optimal processing technology Incombination with microhardness and TEM analysis for: room temperature,4Gpapressure, reverse ten laps. It is shown by XRD and TEM analysis that the average grainsize of Al-Zn-Mg-Cu alloy different the initial state heat treatment after high pressuretorsion is73~84nm, indicating very high dislocation density and severe grain sizedecrease as compared with the average block coarse grain size. Away from the center ofthe circle2mm sample overall organization to achieve uniform stable condition,microhardness of the three states after high pressure torsion are more than250HV onaverage, tensile properties significantly increased, solid solution state tensile strength of764MPa, peak aging state of tensile strength of916MPa and ageing state of tensilestrength are865MPa. TEM analysis shows that the second phase particle dispersiondistribution, grain size nano, dislocation multiplication is the root cause excellentmechanical properties. In order to compare with mechnical properties of Al-Zn-Mg-Cu alloy, twoapproaches including the conventional rolling and annealing processing follow-upmeasures with high pressure were applied. It is shown that, when subjected toconventional rolling, material hardness increased with the increase of reduction ofhardness rising, Al-Zn-Mg-Cu alloy craze which is rolled reduction90%, microhardnessis201HV, the tensile strength of616MPa; Sample of SS state after the HPT process5.5GPa,200℃heat1hour heat treatment, the results show that the high pressure of thesample after heat treatment, down significantly compared with before annealing, alongthe radius variation trend is consistent, the average microhardness is176HV.