新聞資訊
兩階段軋制變形過程中高強(qiáng)鋁合金析出相與晶粒結(jié)構(gòu)演變及其對性能的影響
發(fā)布人：上海艾荔艾合金股份有限公司www.shailiai.cn
更新時(shí)間：2016-06-24
與7055鋁合金的傳統(tǒng)熱軋(CHR)對比, 制定了新的兩階段熱軋工藝(DHR), 分別采用 CHR 和 DHR 對 7055 鋁合金板材進(jìn)行軋制, 研究了 DHR 工藝對7055鋁合金析出相和亞結(jié)構(gòu)的影響, 分析了 DHR 和 CHR 處理后合金組織、力學(xué)性能的差異.
兩階段軋制變形過程中高強(qiáng)鋁合金析出相與晶粒結(jié)構(gòu)演變及其對性能的影響PRECIPITATES AND THE EVOLUTION OF GRAIN
STRUCTURES DURING DOUBLE-STEP ROLLING OF
HIGH-STRENGTH ALUMINUM ALLOY AND RELATED
PROPERTIES
與 7055 鋁合金的傳統(tǒng)熱軋(CHR)對比, 制定了新的兩階段熱軋工藝(DHR), 分別采用 CHR 和 DHR 對
7055 鋁合金板材進(jìn)行軋制, 研究了 DHR 工藝對 7055 鋁合金析出相和亞結(jié)構(gòu)的影響, 分析了 DHR 和 CHR
處理后合金組織、力學(xué)性能的差異. 結(jié)果表明: 增加預(yù)變形量可提高析出相的球化程度(改變析出相形貌)
但不影響其面積分?jǐn)?shù); 中間高溫短時(shí)退火可形成大量有序排布的亞結(jié)構(gòu); 后續(xù)進(jìn)一步熱軋過程中, 仍存在
的大量球形析出相釘扎位錯(cuò)和亞晶界, 且隨累積應(yīng)變增大, 小角晶界逐漸轉(zhuǎn)變成大角晶界而使晶粒細(xì)化.
采用最佳的形變熱處理工藝(固溶+預(yù)變形(300 ℃, 20%+中間退火(430 ℃, 5 min)+熱變形(400 ℃, 60%))可在
保證高強(qiáng)度的同時(shí)使 7055 鋁合金板材斷后延伸率比 CHR 工藝提高約 25%.
The Al-Zn-Mg-Cu series alloys has been widely used in the aircraft, automotive, ship-building and
nuclear industries for the advantages of excellent combination of low density, high strength to weight ratio, good
toughness and high corrosion resistance, etc.. Most of the researchers focused on alloying and heat treatment at
aging temperature, however, rare work had paid attentions on the deformation process, and the microstructure
evolution and mechanical properties has not been analyzed completely. Grain refinement can not only improve the
strength and hardness, but also the plasticity and toughness of the alloy. Thermo mechanical treatment is an
efficient and economical treatment for obtain grain refinement by a combination the deformation and heat
treatment. In the present work, an improved thermo-mechanical processing, double step hot rolling (DHR),
including low temperature pre-deformation, intermediate short-term annealing and final hot rolling has been
proposed, aiming to investigate the microstructural evolution, deformation-induced precipitation and grain
refinement mechanism of the alloys during the DHR process. A 7055 aluminum plate has also been manufactured
by the conventional hot rolling (CHR) route. The corresponding microstructure evolution and mechanical
properties were investigated by OM, XRD, TEM, SEM, EBSD and tensile test. The results reveal that the grain
refinement is mainly preceded via dislocation rearrangement and low angle grain boundaries migration, which in
turn leads to the pinning effects of deformation induced precipitates. Low temperature pre-deformation can
accelerate the formation and spheroidization of fine precipitates. The pre-deformation makes influence on the
morphology and average size of precipitates without changing their area fraction. The precipitates generated by
the pre-deformation can exert significant drag force to the migration of the grain boundaries and dislocation
movements, which subsequently promotes the formation of dislocation cells. Although some smaller particles
have been dissolved into the matrix during intermediate annealing treatment, some particles are still fine and can
pin the dislocation boundaries. At the same time, the activated dislocation boundaries rearranged to form polygon
sub-grains. Grains are further elongated after the final hot rolling. The low angle grain boundaries (like sub-grain
boundaries) into high angle grain boundaries transition will be accelerated if the motion of boundaries is impeded
by the particles. And the new small grains formed near the original grain boundaries can finally cause the
fine-grained structures. The results indicate that the optimum thermo-mechanical treatment of 7055 aluminum
alloy may be solid heat treatment + pre-deformation (300 ℃, 20%) + intermediate annealing (430 ℃, 5 min) + hot deformation (400 ℃, 60%). The elongation of the alloy produced by the proposed process can increase by 25%
without strength loss comparing with that of conventional hot rolling. And the present DHR process is supposed to
be a good alternative manufacturing process for the Al alloys to obtain fine grain structured heat-treatable sheets. ?
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