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MICROSTRUCTURAL EVOLUTION OF AS-CAST ZA27 ALLOY DURING compressive creep

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Acta Metallurgica Sinica(English Letters) 2003年第5期16卷 335-341页

作者： X.W.Wei B.L.Shen DepartmentofMaterialsScienceandEngineering SichuanInstituteofTechnologyChengdu610039China DepartmentofMetalScience SichuanUniversityChengdu610065China

Phase transformation and micro structural change of an as-cast ZA27 alloy were investigated during compressive creep by X-ray diffraction technique, SEM and TEM. compressive creep induced decomposition of α metastable η' phase and a four-phase transformation, α + ε → T' + η and T' → θ, occurred during the compressive creep testing. The occurrence of negative creep in the alloy resulted from the volume expansion caused by the four-phase transformation. A micro structural change was also observed from a lamellar structure into a spheroidized structure in higher creep strain of tested specimens. It provided evidence of compressive creep induced phase transformation which occurred in ageing process.

关键词： microstructure change compressive creep ZA27 alloy

Microstructures,mechanical properties and compressive creep behaviors of as-cast Mg-5%Sn-(0-1.0)%Pb alloys

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Journal of Central South University 2011年第2期18卷 290-295页

作者：王卿陈云贵肖素芬刘红梅唐永柏赵源华 School of Materials Science and Engineering Sichuan University Department of Chemical and Materials Engineering The University of Auckland

The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-（0-1.0）%Pb （mass fraction） alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic a-Mg and Mg2Sn phase. The addition of Pb can refine the size of Mg2Sn phase and grain size, reduce the amount of Mg2Sn phase at grain or inter-dendrite boundaries and change the distribution of Mg2Sn phase. Pb exists in the Mg2Sn phase or dissolves in a-Mg matrix. The mechanical properties of the tested alloys at room temperature are improved with the addition of Pb. When the Pb content is over 0.5%, the mechanical properties are decreased gradually. The Mg-5%Sn-0.5%Pb shows the best ultimate tensile strength and elongation, 174 MPa and 14.3%, respectively. However, the compressive creep resistance of the Mg-Sn-Pb alloys is much lower than that of the Mg-Sn binary alloy at 175℃ with applied load of 55 MPa, which means that Pb has negative effects on the compressive creep resistance of the as-cast Mg-Sn alloys.

关键词： Mg-Sn-Pb alloy microstructures mechanical properties compressive creep Mg2Sn phase

Visco-elastoplastic damage constitutive model for compressed asphalt mastic

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Journal of Central South University 2014年第10期21卷 4007-4013页

作者：曾国伟杨新华白凡高虎 School of Civil Engineering and Mechanics Huazhong University of Science and Technology School of Science Wuhan University of Science and Technology

In order to describe the three-stage creep behavior of compressed asphalt mastic, a visco-elastoplastic damage constitutive model is proposed in this work. The model parameters are treated as quadratic polynomial functions with respect to stress and temperature. A series of uniaxial compressive creep experiments are performed at various stress and temperature conditions in order to determine these parameter functions, and then the proposed model is validated by comparison between the predictions and experiments at the other loading conditions. It is shown that very small permanent deformation at low stress and temperature increases rapidly with elevated stress or temperature and the damage may initiate in the stationary stage but mainly develops in the accelerated stage. Compared with the visco-elastoplastic models without damage, the predictions from the proposed model is in better agreement with the experiments, and can better capture the rate-dependency in creep responses of asphalt mastic especially below its softening point of 47 ℃

关键词： asphalt mastic visco-elastoplastic damage model compressive creep