Study On The Anisotropy Of Aluminum Alloy Sheets

For its excellent lightweight, high strength, high corrosion resistance and easy-forming, etc, aluminum alloy sheets are widely used in all the field.The differences in the aluminum sheet mechanical properties under conditions of different orientations,is called anisotropy. Anisotropy affected by alloying elements, heat treatments and rolling conditions is an important aspect of sheets applications research. Strength of the sheets in the rolling direction generally exceed the rolling direction, but sometimes the strength vertical rolling direction exceed rolling direction,called reverse anisotropy.In this paper, tensile mechanical properties test,OM microstructure observation,SEM and TEM electron microscopy observation to organization have been used, so that to study the anisotropy of 7050、2024、5083、Al-Mg-Si、 mid-strength and weldable Al-5.0Zn-1.6Mg alloy sheets and 7050 alloy sheets of different heat treatments,7150 alloy sheets contain different Zr.The results summarized are as follows:(1)In addition to the 7050 and mid-strength and weldable 6#Al-5.0Zn-1.6Mg alloy,2024,5083,1#、2#、3#、4#、5#mid-strength and weldable Al-5.0Zn-1.6Mg,31 #Al-0.5Mg-0.3Si,40#Al-1.0Mg-0.9Si-0.8Mn-0.4Cu alloy sheets after heat treatments do not show reverse anisotropy of mechanical properties,aluminum alloy sheets add Zr elements tend to show reverse anisotropy of mechanical properties.(2)Add about 0.2% Zr refine grains significantly in mid-strength and weldable Al-5.0Zn-1.6Mg alloy sheets after heat treatments,sheets contain Al3Zr,needle phase, length 900nm～9μm,grain boundaries precipitates composition close to Al2Mg3Zn3 phase, size of about 50nm, the tissue partly occurs uneven fibrous structure of non-recrystallized,the strength of sheet increase and tend to show reverse anisotropy, while elongation decrease.(3) 7050 alloy sheets containing Zr after heat treatment appear reverse anisotropy of mechanical properties, the second stage 482 ℃ increase sheets’degree of reverse anisotropy after 470 ℃× 1h+482℃×different times of the two-stage solution treatments.(4) 7050 alloy sheets after 470℃ ×1h+482 ℃ × different times of the two-stage solution treatments contain excess phase of undissolved circular Al2CuMg, irregular oval Al7Cu2Fe,and rectangular Al3 (Zr1-xTix), after 470℃×1h+482℃×30min solution treatment,the coarse phase fully dissolves, the level of recrystallization is low, the subgrain organization grow slowly, the average grain size of the alloy maintains at a lower level, matrix after aging has the maximum strength.(5) Al-6.4Zn-2.35Mg-2.2Cu alloy sheets contained Zr appear reverse anisotropy of mechanical properties, Zr refines grain size significantly so that grain with Zr content from 0.04%to 0.20%reduces largely, when content of Zr reach to 0.16%, tissue of rolling surface largely occurs uneven fibrous band of non-recrystallized,which increases gradually.(6) Al-6.4Zn-2.35Mg-2.2Cu alloy sheets having different amounts of Zr mainly contain excess phase of regular circular S(Al2CuMg),which size about 2-6μm, irregular elongate Fe containing phase,which size about 3μm, and elongated or rectangular Al3Zr phase,while Zr content reaches 0.16%, Al3Zr type of dispersed phase begin to appear obviously.