| 摘要 |
The present invention relates to a method for producing a high strength AI-Z n- Cu-Mg alloy with an improved fatigue crack growth resistance and a high dama ge tolerance, comprising the steps of casting an ingot with the following composition (in weight percent) Zn 5.5- 9.5, Cu 1.5 - 3.5, Mg 1.5 - 3.5, Mn < 0.25, Zr < 0.25, Cr < 0.10, Fe < 0.25, Si < 0.25, Ti < 0.10, Hf and/or V < 0.25, other elements each less than 0.05 and less than 0.15 in total, balanc e aluminium, homogenising and/or pre-heating the ingot after casting, hot working the ingot and optionally cold working into a worked product of more than 50 mm thickness, solution heat treating, quenching the heat treated product, and artificially aging the worked and heat-treated product, wherein the aging step comprises a first heat treatment at a temperature in a range of 105~C to 135~C for more than 2 hours and less than 8 hours and a second heat treatment at a higher temperature than 135~C but below 170~C for more than 5 hours and less than 15 hours. The product achieved by the method exhibits a compression yield strengh of at least 510 Mpa and an ST elongation at S/2 of at least 3.0 %. The invention concerns a weldable plate product of such high strength Al-Zn-Cu-Mg having a thickness of more than 50 mm and an aircraft structural member produced from such alloy.
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