新聞資訊
定向凝固U720Li合金的高溫塑性變形行為
發布人：上海艾荔艾合金股份有限公司www.shailiai.cn
更新時間：2016-01-12
采用熱模擬實驗研究了定向凝固與等軸晶 U720Li 合金的高溫塑性變形行為,利用 OM,SEM 和 EBSD 分析了不同變形條件下合金的組織特征及動態再結晶機制.
定向凝固U720Li合金的高溫塑性變形行為PLASTIC DEFORMATION BEHAVIOR OF DIRECTIONALLY SOLIDIFIED?U720Li ALLOY AT ELEVATED TEMPERATURE
采用熱模擬實驗研究了定向凝固與等軸晶 U720Li 合金的高溫塑性變形行為,利用 OM,SEM 和 EBSD 分析了不同變形條件下合金的組織特征及動態再結晶機制.結果表明,定向凝固與等軸晶合金的變形抗力均隨變形溫度升高而降低.定向凝固 U720Li 合金沿垂直柱狀晶方向變形時變形抗力較低,枝晶間協調變形能力良好,未出現裂紋.與等軸晶合金相比,相同變形條件下定向凝固合金的動態再結晶組織均勻;高溫塑性變形過程中,定向凝固合金的動態再結晶主要以晶界弓彎和位錯塞積方式形核.定向凝固 U720Li 合金的變形激活能為 766 kJ/mol,比等軸晶合金降低了 38.6 %,定向凝固合金呈現出更好的熱加工特性.?
U720Li, a kind of precipitation type nickel-based superalloy, shows excellent mechanical properties?at elevated temperature, which is also known as the difficult-to-deform alloy because of the high-alloying. To?solve its deformation problem, new methods would be developed to enlarge the temperature deforming window?and improve its plasticity. The hot compression deformation behaviors of directionally solidified and equiaxed?grain U720Li alloys were studied by the MMS-300 testing system, as well as the dynamic recrystallization?nucleation and growth mechanisms during the hot deformation were discussed. The microstructural characteristics?of the alloy under different deformation conditions were examined using OM, SEM and EBSD. The results show?that the deforming resistances of both directionally solidified and equiaxed grain U720Li alloys decrease with the?increasing of deforming temperature. When the angle between the compression deforming direction and?dendrite growth direction is 90°, the deforming resistance of directionally solidified U720Li alloy would be lower.?With this direction, the coordination deformation between the dendrites becomes better and no crack can be found?after deformation, which indicates that the deforming ability is best along ?90°and it can be considered as the?optimal deforming direction for directionally solidified U720Li alloy. Compared with equiaxed grain alloy,?directionally solidified U720Li alloy performs higher deformation ability and more homogenous microstructures.?During the deformation of directionally solidified U720Li alloy, bulging nucleation of grain boundary migration?and dislocation pile-up induced nucleation are found as the main mechanism for the nucleation of dynamic?recrystallization. In addition, the deformation activation energy of directionally solidified U720Li alloy is 766?kJ/mol, which is 482 kJ/mol lower than that of equiaxed grain alloy, indicating the directional solidified U720Li?alloy exhibits better hot-working plasticity.?
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