扩散退火对2090-Ce铝锂合金组织和性能的影响

Effect of Diffusion Annealing on Microstructure and Mechanical Properties of 2090-Ce Al-Li Alloy

研究了含0．12％～0．15％Ce的2090合金铸锭扩散退火工艺参数对合金元素在晶粒内部的分布、合金板材力学性能及强化相的分布与形态的影响。研究结果表明，对于2090－Ce合金铸锭，采用350℃×10h＋500℃×16b的均匀化处理，可使板材最终固溶时效后的强度提高；采用450℃×10h＋500℃×10h＋520℃×6h的均匀化处理，可使板材最终固溶时效后的断裂韧度及伸长率提高。第一段和第三段均匀化温度越高，合金板材的强度越低。第一段均匀化温度越高或第二段均匀化时间越长，组织中的β′相越粗大。扩散退火工艺对2090－Ce合金板材固溶时效后的强化相δ′及T1的形态与分布能产生间接的影响。降低第一段的均匀化温度，可使组织中获得细小的δ′／β′复合相，但使T1相分布和尺寸不均匀；较高的第一段均匀化温度和较长的第二段均匀化时间可使δ′／β′复合相中的δ′包复层分解成细小的颗粒状，并使T1相粗化；较高的第三段均匀化温度除使T1根粗化外，并促使其沿晶析出，同时使δ′相减少。

The effect of the process parameters of diffusion annealing for the ingots of alloy 2090 containing 0.12% ~0.15% Ce on the distribution of alloying element inside the grains, mechanical properties of the alloy sheets and the distribution or morphology of the dispersoids formed during hornogenizlng and the precipitates formed during ageing was studied. The results indicate that with the increase of first-stage or third-stage homogenization temperature the strength ot the as-aged sheets decreases, and rnedium first-stage or third-stage temperature can bring a certain benefit of fracture toughness and elongation to the sheets. Therefore, the sheets willdisplay a higher strength by the diffusion annealing of 350℃×10h＋500℃×16h or may show a higher fracture toughness and elongation by 450℃×10h＋500℃×10h＋520℃ ×6h to ingots. Higher first-stage temperature orlonger second-stage time of homogenization can make β' (Al3Zr) and T1 (Al2CuLi) compounds thicker and δ'(Al3Li)coats in the duplex δ'/β' precipitates split into granular shape. In the microstructure of the sheets there are some finer and more dispersed duplex δ' /β' precipitates and non-uniform T1 phases in distribution and size under lower first-stage temperature. Higher third-stage temperature will cause the volume fraction of δ'particles to decreape and promote T1 phases to precipitate along grain boundaries with the addition of thick T1 phases inside grains.