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the application of SHT forming to form structural parts. The process steps in the SHT forming process chain are shown in Fig. 1. The origin of SHT forming came from retrogression and reageing heat treatment (RRA). BARUCH and RAMAT [4] invented a heat treatment for AW-7075-T6 known as retrogression and re-ageing (RRA). RRA was claimed to substantially reduce the susceptibility of the alloy to stress......
but was susceptible to SCC. Many efforts have been put forward to increase strength and SCC resistance. Retrogression and reaging (RRA) [10-13] decreased the SCC susceptibility and kept the strength levels similar to T6 temper. Repetitive- RRA could further improve SCC resistance with retention of strength compared to RRA temper [14-15]. However, the retrogression temperature was in the range of 180-260 °C......
内容之一.单级时效处理(T6)能析出高密度的晶内析出相,故可获得较高的强度,但耐蚀性较差[3];双级过时效处理(T7X)的晶界析出相变得粗大,连续,可得到较高的耐蚀性,但强度降低较多[4];回归再时效(Retrogression and re-ageing heat treatments, RRA)能同时兼顾强度和耐蚀性的要求,是目前较好的一种时效制度,但不利于厚板的处理[5].RRA是在峰时效..., LIU Y B, ZENG S M. Retrogression and re-aging treatment of Al-9.99%Zn-1.72%Cu- 2.5%Mg-0.13%Zr aluminum alloy[J]. Transactions of Nonferrous Metals Society of China, 2006, 16(5): 1163-1170. [2] 郑子樵, 李红英......
] known as retrogression and reaging (RRA) was developed to enhance the SCC resistance of 7xxx alloys without considerable change in strength when compared to the T6 temper. The RRA treatment consists of annealing process of T6 sample at 180-240 °C for 5-2400 s called as retrogression, which was followed by re-aging implementing similar conditions as used for the original T6 aging. During......
]. 1974-12-24. [6] WU X J, RAIZENNE M D, HOLT R T, et al. Thirty years of retrogression and re-aging (RRA)[J]. Canadian Aeronautics and Space Journal, 2001, 47(3): 131-138. [7] ROMETSCH P A, ZHANG Y, KNIGHT S... evolution rules for aluminum alloy 7050 during retrogression heating up[J]. Rare Metal Materials and Engineering, 2011, 40(7): 1295-1299. [11] REDA Y, ABDEL-KARIM R, ELMAHALLAWI I. Improvements......
and Engineering A, 2004, 379(1-2): 321-326. [8] TALIANKER M, CINA B. Retrogression and reaging and the role of dislocations in the stress corrosion of 7000-type aluminum alloys
, and the grain boundary precipitates change to be coarser and more discrete. Based on the DSC results of T651 sample mentioned above and some reported work[12], it can be considered that after retrogression... and boundaries) grow up. Fig.8 TEM micrograph of 7B04 alloy after retrogression at 180 ℃ for 1 h Fig.9(a) shows a TEM micrograph of the alloy after RRA treatment. It can be observed that the precipitates......
. However, the strength of the 7??? series Al alloys with these over-aging treatments is decreased. The 7??? series Al alloys with retrogression and re-aging (RRA) treatment possess high strength and good SCC resistance[4-5]. However, the RRA treatment can not be used for large-section Al alloys due to its very short retrogression time[6]. To keep the high strength of the 7??? series Al alloys......
of GBPs also improves SCC resistance by reducing the electrochemical activity to increase the crack initiation resistance, inversely for Zn [8]. Over-aging and retrogression and reaging (RRA) treatments..., 1972, 12(3): 3191-3200. [6] PARK J K, ARDELL A J. Effect of retrogression and reaging treatments on the microstructure of Al-7075-T651 [J]. Metallurgical and Materials Transactions A, 1984, 15 (8......
-Zn-Mg-Cu合金具有高的比强度,易加工成型以及较好的焊接性能,但其对应力腐蚀和剥落腐蚀比较敏感,能够提升该合金综合性能的回归再时效(Retrogression and reaging,RRA),热机械处理(TMT)等工艺越来越受到关注[4-8].CINA[6]提出的RRA工艺可保证该系合金同时拥有高强度和优异的耐腐蚀性能;OSTERMANN等[9]的研究结果表明,FTMT能够使Al-Zn-Mg... on precipitate composition in Al-Zn-Mg-Cu alloys[J]. Acta Materialia, 2010, 58(1): 248-260. [2] MARLAUD T, DESCHAMPS A, BLEY F, LEFEBVREC W. Evolution of precipitate microstructures during the retrogression......