【正文】 ? metallographic examination shall be carried out at 500 times magnification。s facility for not less than five years. EN 4852:2020 (E) 9 Licensed Copy: Institute Of Technology Tallaght, Institute of Technology, Tue Nov 14 09:45:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI For lot acceptancepurposes resistance to stresscorrosion cracking for each lot of material shall be established by testing the previously selected tensile test specimens to the criteria shown in Table 38. 8 Exfoliation corrosion resistance (5xxx series alloys) Products made of alloys EN AW5086, EN AW5083 and EN AW5383 in the H116 temper shall be capable of exhibiting no evidence of exfoliation corrosion when subjected to ASTM G6695 accelerated exfoliation corrosion susceptibility test. The test shall be carried out on full thickness testpieces for material less than 2,5 mm in thickness. For material 2,5 mm or more in thickness, 10 % of the thickness shall be removed by machining, from one asrolled surface, and both the machined and asrolled surfaces submitted to the test and evaluated. For lotacceptance purposes, the acceptability of each lot of material mentioned in shall be determined by the producer, by metallographic examination of one specimen per lot selected from midsection at one end of a random sheet, plate or coil, using the following procedure: ? a section perpendicular to the rolling surface and parallel to the rolling direction shall be polished (preferably electrolytic polish) and then microetched for 3 min, using a solution of 40 ml 85 % phosphoric acid in 60 ml distilled water, at (35 ? 5) 176。 ? testpieces shall be stressed in the short transverse direction with a stress level of 75 % of the specified proof stress。 it can also be used for a quick semiquantitative check of the thermal treatment to which the material has been submitted or, as a first approach, for material identification purpose. However its accuracy is generally less than can be expected from a tensile test which it cannot replace. EN 4852:2020 (E) 8 Licensed Copy: Institute Of Technology Tallaght, Institute of Technology, Tue Nov 14 09:45:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI NOTE Hardness can be measured at different locations, . on the surface of the product or on the tensile specimen. For some materials, results can be different. The values in Tables 2 to 39 are typical Brinell hardness (HBW) values for a test carried out according to EN ISO 65061 with a 2,5 mm diameter steel ball. They are given for information only. If the Brinell hardness test is not possible (because of thin gauge or soft temper) then Vickers hardness test, according to EN ISO 65071, can be used. In that case the values wi ll be approximately 10 % above the stated Brinell values. Table 1, given for convenience, shows for several HBW values the minimum gauge down to which the hardness measurement remains valid, according to the rules stated in EN ISO 65061, using a 2,5 mm diameter steel ball and a load of 612,9 N. Table 1 — Minimum material gauge and Brinell hardness values Brinell hardness (HBW) 30 40 50 60 70 80 90 100 minimum gauge (mm) 2,1 1,6 1,3 1,1 0,91 0,80 0,71 0,64 Brinell hardness (HBW) 110 120 130 140 150 160 170 180 minimum gauge (mm) 0,58 0,53 0,49 0,45 0,42 0,40 0,37 0,35 6 Electrical conductivity Electrical conductivity measurements are required for lot acceptancepurposes, in the case of alloy EN AW7075 in the tempers T73, T7351, T76 and T7651, in order to assess the resistance to stresscorrosion cracking or the exfoliationcorrosion resistance of the material as applicable. The specimen for electrical conductivity testing shall be taken adjacent to the tensile test specimen. The measurement shall be carried out by the eddycurrent method as specified in EN 20201. The reference blocks to be used shall be agreed between producer and purchaser. The results shall be rounded to the nearest 0,1 MS/m, using the rounding rules set out in annex A. The acceptance criteria are specified in Table 38. 7 Stresscorrosion resistance Plate made of alloy EN AW7075 in the T73 and T7351 tempers and over 25 mm in thickness, shall be capable of exhibiting no evidence of stresscorrosion cracking when subjected to ISO 9591 accelerated stresscorrosion cracking test. For the purpose of this standard the following provisions shall apply: ? a minimum of three adjacent replicate test pieces shall be taken from each specimen and submitted to the test。 ? width of the test piece shall be at least 20 mm and preferably 40 mm to 50 mm. For material less than 20 mm wide, the width of the testpiece shall be the full width of the material。, as applicable, around a pin having a radius equal to k times the thickness t of the sheet, strip or plate (. 2,5 t) without cracking. Remended values of the minimum bend radii for different alloys, tempers and thicknesses are given in Tables 2 to 39. Compliance with these values and/or conduct of the test is only required when so specified on the order. The test shall be carried out in accordance with EN ISO 7438, particular attention being paid to the following: ? bend test shall be carried out on a specimen taken adjacent to the tensile test specimen。 ? for determination of pliance, proof stress and tensile strength values shall be rounded to the nearest 1 MPa and elongation values to the nearest 1 % using the rounding rules set out in annex A. 4 Bend test Sheet, strip and plate shall be capable of being bent cold throu