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Grain size dependence of annealing strengthening of an extruded Mg-Gd-Zn alloy subjected to pre-compression deformation

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Journal of Magnesium and Alloys 2022年第12期10卷 3576-3588页

作者： Qinghang Wang Siyuan Chen Bin Jiang Zhaoyang Jin Lingyu Zhao Junjie He Dingfei Zhang Guangsheng Huang Fusheng Pan School of Mechanical Engineering Yangzhou UniversityYangzhou225127China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing400044China School of Materials and Energy Yunnan UniversityKunming650599China

In this work, pre-strain annealing strengthening(PSAS) effect was investigated in an extruded Mg-1.0Gd-1.5 Zn(wt.%) alloy with respect to different grain sizes. The evolution of microstructures was provided by scanning electron microscopy(SEM), electron backscattered diffraction(EBSD), transmission electron microscopy(TEM) and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM) under the initial state, pre-compression, intermediate annealing and re-compression conditions. The obtained results showed a grain size-dependent PSAS effect in the alloy. The sample with larger grain sizes corresponded to a higher strengthening effect, which mainly resulted from a more remarkable hindrance for the growth of existing twins and a larger proportion of activation for the nucleation of new twins. This was closely associated with the increase of back stress and friction stress for twin boundary motion impeded by the larger restraint of dislocations, the higher stress field surrounding solutes and the more Zn segregation. In addition to twinning behavior, Guinier preston(G.P.) zones on basaldislocations were found after intermediate annealing and provided an extra strengthening by inhibiting the motions of gilding pre-existing dislocations and newly formed ones, but it was independent on the grain size.

关键词： Mg-Gd-Zn alloy Grain size pre-compression Annealing strengthening Twinning

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Numerical Investigation of a Centrifugal Compressor with a pre-compression Wedge Diffuser under High Subsonic Conditions

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Journal of Thermal Science 2020年第4期29卷 945-954页

作者： WANG Yi LI Qingkuo BAI Huan ZHOU Xueqi LU Xin’gen School of Aeronautics and Astronautics Central South UniversityChangsha 410083China AECC Hunan Aviation Powerplant Research Institute Hunan Key Laboratory of Turbomachinery on Small and Medium Areo-EngineZhuzhou 412002China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China

As the total pressure ratio of centrifugal compressors increases, the diffuser inlet flow becomes highly subsonic or even supersonic, which causes additional shock loss. The shock loss leads the stage performance to drop greatly. pre-compression is an efficient method for reducing shock loss and improving the stage performance. To study the effect of wedge diffusers with pre-compression blades on centrifugal compressor performance, wedge diffusers with various pre-compression angles, divergence angles and numbers of blades were designed and investigated via a numerical method. As a result, it is found that the compressor stage achieves high peak efficiency when the pre-compression angle ranges from 2.5° to 5.5° and when the divergence angle ranges from 7° to 9°. As the number of blades increases, the total pressure ratio and adiabatic efficiency of the compressor stage increase slightly, whereas the surge margin of the stage decreases.

关键词： wedge diffuser pre-compression high Subsonic centrifugal compressor

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Improving the room-temperature bendability of Mg-3Al-1Zn alloy sheet by introducing a bimodal microstructure and the texture re-orientation

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International Journal of Minerals,Metallurgy and Materials 2022年第7期29卷 1322-1333页

作者： Chao He Yibing Zhang Ming Yuan Bin Jiang Qinghang Wang Yanfu Chai Guangsheng Huang Dingfei Zhang Fusheng Pan State Key Laboratory of Mechanical Transmissions College of Materials Science and EngineeringChongqing UniversityChongqing 400044China School of Chemistry and Materials Science Hubei Engineering UniversityXiaogan 432000China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China School of Mechanical Engineering Yangzhou UniversityYangzhou 225127China School of Mechanical and Electrical Engineering Shaoxing UniversityShaoxing 312000China

A significant enhancement of bendability was achieved by the introduction of bimodal microstructure for AZ31B alloy sheets via pre-compression and subsequent annealing(PCA)process.This combined treatment led to the c-axis of the extracted samples that were inclined by 30°to the rolling direction(30°sample)further shifting toward the rolling direction(RD)and resulting in a higher Schmid factor(SF)value of basal slip under the RD tensile stress.Furthermore,the bimodal microstructure that was introduced by the PCA process broke the damage bands(DBs)in the initial hot rolled AZ31B alloy sheets and gave rise to a more uniform strain distribution in the outer tension region of the bending samples,in which the tensile deformation was accommodated by the equally distributed{101^(-)2}tension twinning and basal slip.Consequently,the bimodal microstructure,shifted basal texture and the modification of DBs were responsible for the significant enhancement in the bendability of the AZ31 alloys.

关键词： magnesium alloy pre-compression texture bimodal microstructure bendability

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