Mg-Zn-Ca-Mn series alloys are developed as promising candidates of 5G communication devices with excellent thermal conductivities,great ductility,and acceptable strength.In present paper,Mg-x Zn-0.4Ca-0.2Mn(x=2wt%,4wt...Mg-Zn-Ca-Mn series alloys are developed as promising candidates of 5G communication devices with excellent thermal conductivities,great ductility,and acceptable strength.In present paper,Mg-x Zn-0.4Ca-0.2Mn(x=2wt%,4wt%,6wt%)alloys were prepared by a near-solidus extrusion and the effect of Zn content on mechanical and thermal properties were investigated.The results showed that the addition of minor Ca led to the formation of Ca_(2)Mg_(6)Zn_(3) eutectic phase at grain boundaries.A type of bimodal microstructure occurred in the as-extruded alloys,where elongated coarse deformed grains were embedded in refined recrystallized grains matrix.Correspondingly,both yield strength and ductility of the alloys were significantly enhanced after extrusion due to the great grain refinement.Specially,higher Zn content led to the increment in yield strength and a slight reduction in elongation due to the larger fractions of second phase particles.The room temperature thermal conductivity of as-extruded alloys was also improved compared with that of as-cast counterparts.The increment of Zn content decreased the thermal conductivity of both as-cast and as-extruded alloys,which was due to the increased second phase fraction and solution atoms in the matrix,that hindering the motion of electrons.The as-extruded Mg-2Zn-0.4Ca-0.2Mn(wt%)alloy exhibited the highest elongation of 27.7% and thermal conductivity of 139.2 W/(m·K),combined with an acceptable ultimate tensile strength of 244.0 MPa.The present paper provides scientific guidance for the preparation of lightweight materials with high ductility and high thermal conductivity.展开更多
Dynamic recrystallization(DRX)plays significant roles in manipulating of microstructures during hot deformation and the result mechanical properties;however,the underling mechanism leading to multi scale-microstructur...Dynamic recrystallization(DRX)plays significant roles in manipulating of microstructures during hot deformation and the result mechanical properties;however,the underling mechanism leading to multi scale-microstructures remains poorly understood.Here,the DRX mechanism under wide processing conditions(i.e.950-1200°C,0.001-10 s-1)in Incoloy 028 alloy was investigated,where the relationships among flow stress,Z parameter and grain size,as well as the evolution of characteristic microstructures(grain size,sub-grain boundaries,and high angle grain boundaries),are established.As the values of Z parameters decrease(corresponding to decreased flow stresses),three typical softening mechanisms successively occur,ranging from continuous DRX controlled by dislocation glide,discontinuous DRX dominated by dislocation motion(climb and cross/multiple slip)and grain boundary migration,to dynamic normal/abnormal grain growth resulting from grain boundary migration,with transition regions where two adjacent mechanisms occur simultaneously.Correspondingly,these above three softening mechanisms result in ultrafine,fine and coarse grains,respectively.The present findings demonstrate a comprehensive understanding of DRX mechanism over a wide range of processing conditions,and further provide a new guideline for preparing single crystals.展开更多
基金supported by the Natural Science Basic Research Program of Shaanxi,China(Nos.2022JQ-305 and2022JQ-326)the Qin Chuang Yuan Platform High-Level Talent Project of Innovation and Entrepreneurship(No.QCYRCXM-2023-020)。
文摘Mg-Zn-Ca-Mn series alloys are developed as promising candidates of 5G communication devices with excellent thermal conductivities,great ductility,and acceptable strength.In present paper,Mg-x Zn-0.4Ca-0.2Mn(x=2wt%,4wt%,6wt%)alloys were prepared by a near-solidus extrusion and the effect of Zn content on mechanical and thermal properties were investigated.The results showed that the addition of minor Ca led to the formation of Ca_(2)Mg_(6)Zn_(3) eutectic phase at grain boundaries.A type of bimodal microstructure occurred in the as-extruded alloys,where elongated coarse deformed grains were embedded in refined recrystallized grains matrix.Correspondingly,both yield strength and ductility of the alloys were significantly enhanced after extrusion due to the great grain refinement.Specially,higher Zn content led to the increment in yield strength and a slight reduction in elongation due to the larger fractions of second phase particles.The room temperature thermal conductivity of as-extruded alloys was also improved compared with that of as-cast counterparts.The increment of Zn content decreased the thermal conductivity of both as-cast and as-extruded alloys,which was due to the increased second phase fraction and solution atoms in the matrix,that hindering the motion of electrons.The as-extruded Mg-2Zn-0.4Ca-0.2Mn(wt%)alloy exhibited the highest elongation of 27.7% and thermal conductivity of 139.2 W/(m·K),combined with an acceptable ultimate tensile strength of 244.0 MPa.The present paper provides scientific guidance for the preparation of lightweight materials with high ductility and high thermal conductivity.
基金This work was supported by the National Key R&D Program of China(grant numbers 2017YFB0703001,2017YFB0305100)the Natural Science Foundation of China(grant numbers 51431008,51790481,51804336,51901185)+1 种基金the Research Fund of the State Key Laboratory of Solidification Processing(grant numbers 2019-BJ-04,2019-TZ-01)and the Natural Science Basic Research Plan in Shaanxi Province of China(grant number 2019JM-132).We would like to thank the Analytical&Testing Center of Northwestern Polytechnical University for EBSD and TEM experiments.
文摘Dynamic recrystallization(DRX)plays significant roles in manipulating of microstructures during hot deformation and the result mechanical properties;however,the underling mechanism leading to multi scale-microstructures remains poorly understood.Here,the DRX mechanism under wide processing conditions(i.e.950-1200°C,0.001-10 s-1)in Incoloy 028 alloy was investigated,where the relationships among flow stress,Z parameter and grain size,as well as the evolution of characteristic microstructures(grain size,sub-grain boundaries,and high angle grain boundaries),are established.As the values of Z parameters decrease(corresponding to decreased flow stresses),three typical softening mechanisms successively occur,ranging from continuous DRX controlled by dislocation glide,discontinuous DRX dominated by dislocation motion(climb and cross/multiple slip)and grain boundary migration,to dynamic normal/abnormal grain growth resulting from grain boundary migration,with transition regions where two adjacent mechanisms occur simultaneously.Correspondingly,these above three softening mechanisms result in ultrafine,fine and coarse grains,respectively.The present findings demonstrate a comprehensive understanding of DRX mechanism over a wide range of processing conditions,and further provide a new guideline for preparing single crystals.