首页|采用原位热机械处理技术避免时效强化合金的晶界析出和强韧损失

采用原位热机械处理技术避免时效强化合金的晶界析出和强韧损失

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为了避免时效强化合金的晶界析出对断裂伸长率造成致命损失,提出一种原位热机械处理技术新方案.对7075Al合金在250℃下进行8道次等径角挤压变形,在制备超细晶基体的同时,将高密度纳米析出相引入晶粒内部,从而避免晶界析出.拉伸实验结果表明,该超细晶7075Al合金具有优异的力学性能(屈服强度350 MPa、抗拉强度500 MPa、均匀伸长率18％和断裂伸长率19％),而相应的超细晶1050Al合金仅具有170 MPa的屈服强度、180 MPa的抗拉强度、2.5％的均匀伸长率和7％的断裂伸长率.断口分析结果表明,超细晶7075Al和1050Al合金颈缩区的高密度微观剪切变形带由晶界集体滑动所致;超细晶7075Al合金中纳米析出相的引入能减弱剪切断裂的趋势,从而使塑性变形更加均匀,拉伸塑性提高.与变形处理后的时效退火不同,在原位热机械处理过程中超细晶晶界的动态形成晚于晶内纳米析出,从而避免晶界析出.
In situ thermomechanical processing to avoid grain boundary precipitation and strength-ductility loss of age hardening alloys
To avoid grain boundary (GB) precipitation during aging, a new strategy of in situ thermomechanical processing for age hardening alloys was proposed. Specifically, high-density nanoscale precipitates were introduced into ultrafine grain (UFG) interiors of 7075Al alloy by equal-channel-angular (ECAP) processing at 250℃ for 8 passes, thus avoiding GB precipitation. Tensile test results indicated that the UFG 7075Al alloy exhibits superior mechanical properties (yield strength of 350 MPa, ultimate tensile strength of 500 MPa, uniform elongation of 18％and tensile ductility of 19％) compared with the UFG 1050Al counterpart (yield strength of 170 MPa, ultimate tensile strength of 180 MPa, uniform elongation of 2.5％ and tensile ductility of 7％). Fracture surface morphology studies revealed numerous homogeneous micro shear bands in necking shrinkage areas of both UFG 7075Al and 1050Al alloys, which are controlled by cooperative GB sliding. Moreover, the introduction of nanoscale precipitates in UFG 7075Al matrix weakened the tendency of shear fracture, resulting in a higher tensile ductility and more homogeneous deformation. Different from the GB precipitation during postmortem aging, in situ thermomechanical treatment dynamically formed GBs after precipitation, thus avoiding precipitation on GBs.

age hardening alloysstrengthfracture elongationgrain boundary precipitationin situ thermomechanical processing

赵永好

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南京理工大学 材料科学与工程学院 纳米异构中心,南京 210094

时效强化合金 强度 断裂伸长率 晶界析出 原位热机械处理技术

National Key R&D Program of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaFundamental Research Funds for the Central Universities,China

2017YFA0204403519711125122510230919011405

2021

10.1016/S1003-6326(21)65572-3

中国有色金属学报(英文版)
中国有色金属学会

中国有色金属学报(英文版)

CSTPCDCSCDSCI
影响因子：1.183
ISSN：1003-6326
年,卷(期)：2021.31(5)
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