Mg_(2)Si reinforced Mg-Al based composite with high amount o/silicon was prepared by permanent mould casting,and then extruded by reciprocating extrusion(RE)after the composite was processed by homogenization heat tre...Mg_(2)Si reinforced Mg-Al based composite with high amount o/silicon was prepared by permanent mould casting,and then extruded by reciprocating extrusion(RE)after the composite was processed by homogenization heat treatment.The effect of RE processing on the morphology and size of M92Si and the mechanical properties of the com-posite were investigated,to develop new ways to refine the M928i phase and improve its shape.The result showed that RE was very useful in refining the M92Si phase.The more the RE processing passes,the better the refining effect would be.Moreover,the uniform distribution of M928i phases would be more in the composite.After the composite was processed by RE for 12 passes,most M92Si phases were equiaxed,with granular diameter below 20μm,and distributed uniformly in the matrix of the composite.The mechanical properties of the composite could be increased prominently by RE processing,and were much higher than that in the as-cast state.As the temperature rises,the tensile strength is reduced.For the composite RE processed for 12 passes,the tensile strength,yield strength,and elongation are 325.9 MPa,211.4 MPa,and 3.3%at room temperature,whereas,288.2 MPa,,207.7 MPa,and 7.8%,respectively,at 150℃.In comparison with the properties at room temperature,the tensile strength and yield strength are high and only decrease by 11.6%and 1.8%at 150℃.The M928i reinforced Mg-Al based composite possesses good heat resistance at 150℃.The excellent resistance to effect of heat is attributed to the high melting tempera-ture and good thermal stability of fine Mg2Si phases,which are distributed uniformly in the composite,and effectively hinder the grain boundary gliding and dislocation movement.展开更多
Directionally solidified binary Mg-Al eutectic alloy wires of approximately 5 mm in diameter were produced by the Ohno continuous casting(OCC)process and the microstructure was examined.It was found that the wires pos...Directionally solidified binary Mg-Al eutectic alloy wires of approximately 5 mm in diameter were produced by the Ohno continuous casting(OCC)process and the microstructure was examined.It was found that the wires possess obvious unidirectional growth characteristic along its axial direction.The microstructure consists of parallel columnar grains that resulted from the competitive growth of equiaxed grains solidified on the head of dummy bar.Each columnar grain comprises regular eutectic a-Mg andβ-Mg17 Al12 phases,which grew along the axial direction of the wires.The morphology of the eutectic is mainly lamellar,meanwhile rod eutectic exists.The formation of rod eutectic was attributed to the"bridging effect"caused by incidental elements in the alloy.展开更多
In order to explore the methods to prepare high-strength quasicrystal-reinforced magnesium alloys,the flakes of rapidly solidified Mg-6.4Zn-1.1 Y magnesium alloy with a thickness of 50-60μm were obtained by a melt sp...In order to explore the methods to prepare high-strength quasicrystal-reinforced magnesium alloys,the flakes of rapidly solidified Mg-6.4Zn-1.1 Y magnesium alloy with a thickness of 50-60μm were obtained by a melt spinning single-roller device,and the flakes were then processed into rods by reciprocating extrusion and direct extrusion.The microstructure of the alloy was analyzed by optical microscope and SEM,and the constituent phases were identified by XRD.Phase transformation and its onset temperature were determined by differential thermal analyzer(DTA).The analysis result shows that rapid solidification for Mg-6.4Zn-I.IY alloy can inhibit the eutectic reactions,broaden the solid solubility of Zn inα-Mg solute solution,and impede the formation of Mg3 Y2Zn3 and MgZn2 compounds,and thus help the icosahedral Mg3 YZn6 quasicrystal formed directly from the melt.The microstructure of the flakes consists of theα-Mg solid solution and icosahedral Mg3 YZn6 quasicrystal.Dense rods can be made from the flakes by two-pass reciprocating extrusion and direct extrusion.The interfaces between flakes in the rods can be welded and jointed perfectly.During the reciprocating extrusion and direct extrusion process,more Mg3 YZn6 compounds are precipitated and distributed uniformly,whereas the rods possess fine microstructures inherited from rapidly solidified flakes.The rods contain only two phases:α-magnesium solid solution as matrix and fine icosahedral Mg3 YZn6 quasicrystal which disperses uniformly in the matrix.展开更多
An icosahedral Mg3 YZn6 quasicrystalline phase can be produced in Mg-Zn-Y system alloys when a proper amount of Zn and Y is contained,and it is feasible to prepare the quasicrystal phase-reinforced low-density magnesi...An icosahedral Mg3 YZn6 quasicrystalline phase can be produced in Mg-Zn-Y system alloys when a proper amount of Zn and Y is contained,and it is feasible to prepare the quasicrystal phase-reinforced low-density magnesium alloy.In this article,phase constituents and the effect of reciprocating extrusion on microstructures and properties of the as-cast Mg-6.4Zn-1.1 Y alloy are analyzed.The microstructure of the as-cast Mg-6.4Zn-1.1 Y alloy consists of theα-Mg solid solution,icosahedral Mg3YZn6 quasicrystal,and Mg3 Y2Zn3 and MgZn2 compounds.After the alloy was reciprocatingly extruded for four passes,grains were refined,Mg3 Y2 Zn3 and MgZn2 phases dissolved into the matrix,whereas,Mg3 YZn6 precipitated and distributed uniformly.The alloy possesses the best performance at this state;the tensile strength,yield strength,and elongation are 323.4 MPa,258.2 MPa,and 19.7%,respectively.In comparison with that of the as-cast alloy,the tensile strength,yield strength,and elongation of the reciprocatingly extruded alloy increase by 258.3%,397.5%,and 18 times,respectively.It is concluded that reciprocating extrusion can substantially improve the properties of the as-cast Mg-6.4Zn-1.1 Y alloy,particularly for elongation.The high performance of the Mg-6.4Zn-1.1 Y alloy after reciprocating extrusion can be attributed to dispersion strengthening and grain-refined microstructures.展开更多
基金supported by the Scientific Research Project of Education Department of Shaanxi Province(No.07JK358)the National Natural Science Foundation of China(No.50271054)+1 种基金the Shaanxi Provincial Natural Scientific Research Project(No.2003E111)SRF for ROCS,SEM(101-220325).
文摘Mg_(2)Si reinforced Mg-Al based composite with high amount o/silicon was prepared by permanent mould casting,and then extruded by reciprocating extrusion(RE)after the composite was processed by homogenization heat treatment.The effect of RE processing on the morphology and size of M92Si and the mechanical properties of the com-posite were investigated,to develop new ways to refine the M928i phase and improve its shape.The result showed that RE was very useful in refining the M92Si phase.The more the RE processing passes,the better the refining effect would be.Moreover,the uniform distribution of M928i phases would be more in the composite.After the composite was processed by RE for 12 passes,most M92Si phases were equiaxed,with granular diameter below 20μm,and distributed uniformly in the matrix of the composite.The mechanical properties of the composite could be increased prominently by RE processing,and were much higher than that in the as-cast state.As the temperature rises,the tensile strength is reduced.For the composite RE processed for 12 passes,the tensile strength,yield strength,and elongation are 325.9 MPa,211.4 MPa,and 3.3%at room temperature,whereas,288.2 MPa,,207.7 MPa,and 7.8%,respectively,at 150℃.In comparison with the properties at room temperature,the tensile strength and yield strength are high and only decrease by 11.6%and 1.8%at 150℃.The M928i reinforced Mg-Al based composite possesses good heat resistance at 150℃.The excellent resistance to effect of heat is attributed to the high melting tempera-ture and good thermal stability of fine Mg2Si phases,which are distributed uniformly in the composite,and effectively hinder the grain boundary gliding and dislocation movement.
基金the Shaanxi Provincial Natural Science Research Project(No.2003E111)Scientific research project of Education Department of Shaanxi Province(No.07JK358)the Industrialization Cultivation Project of Education Department of Shaanxi Province(No.04JC24).
文摘Directionally solidified binary Mg-Al eutectic alloy wires of approximately 5 mm in diameter were produced by the Ohno continuous casting(OCC)process and the microstructure was examined.It was found that the wires possess obvious unidirectional growth characteristic along its axial direction.The microstructure consists of parallel columnar grains that resulted from the competitive growth of equiaxed grains solidified on the head of dummy bar.Each columnar grain comprises regular eutectic a-Mg andβ-Mg17 Al12 phases,which grew along the axial direction of the wires.The morphology of the eutectic is mainly lamellar,meanwhile rod eutectic exists.The formation of rod eutectic was attributed to the"bridging effect"caused by incidental elements in the alloy.
基金funded by the National Natural Science Foundation of China(Grant No.50271054)the Shaanxi Provincial Nature Scientific Research Project(Grant No.2003E111)SRF for ROCS,SEM(101-220325).
文摘In order to explore the methods to prepare high-strength quasicrystal-reinforced magnesium alloys,the flakes of rapidly solidified Mg-6.4Zn-1.1 Y magnesium alloy with a thickness of 50-60μm were obtained by a melt spinning single-roller device,and the flakes were then processed into rods by reciprocating extrusion and direct extrusion.The microstructure of the alloy was analyzed by optical microscope and SEM,and the constituent phases were identified by XRD.Phase transformation and its onset temperature were determined by differential thermal analyzer(DTA).The analysis result shows that rapid solidification for Mg-6.4Zn-I.IY alloy can inhibit the eutectic reactions,broaden the solid solubility of Zn inα-Mg solute solution,and impede the formation of Mg3 Y2Zn3 and MgZn2 compounds,and thus help the icosahedral Mg3 YZn6 quasicrystal formed directly from the melt.The microstructure of the flakes consists of theα-Mg solid solution and icosahedral Mg3 YZn6 quasicrystal.Dense rods can be made from the flakes by two-pass reciprocating extrusion and direct extrusion.The interfaces between flakes in the rods can be welded and jointed perfectly.During the reciprocating extrusion and direct extrusion process,more Mg3 YZn6 compounds are precipitated and distributed uniformly,whereas the rods possess fine microstructures inherited from rapidly solidified flakes.The rods contain only two phases:α-magnesium solid solution as matrix and fine icosahedral Mg3 YZn6 quasicrystal which disperses uniformly in the matrix.
基金supported by the National Natural Science Foundation of China(Grant No.50271054)Shaanxi Provincial Nature Scientific Research Project(Grant No.2003E111)SRF for ROCS,SEM(101-220325).
文摘An icosahedral Mg3 YZn6 quasicrystalline phase can be produced in Mg-Zn-Y system alloys when a proper amount of Zn and Y is contained,and it is feasible to prepare the quasicrystal phase-reinforced low-density magnesium alloy.In this article,phase constituents and the effect of reciprocating extrusion on microstructures and properties of the as-cast Mg-6.4Zn-1.1 Y alloy are analyzed.The microstructure of the as-cast Mg-6.4Zn-1.1 Y alloy consists of theα-Mg solid solution,icosahedral Mg3YZn6 quasicrystal,and Mg3 Y2Zn3 and MgZn2 compounds.After the alloy was reciprocatingly extruded for four passes,grains were refined,Mg3 Y2 Zn3 and MgZn2 phases dissolved into the matrix,whereas,Mg3 YZn6 precipitated and distributed uniformly.The alloy possesses the best performance at this state;the tensile strength,yield strength,and elongation are 323.4 MPa,258.2 MPa,and 19.7%,respectively.In comparison with that of the as-cast alloy,the tensile strength,yield strength,and elongation of the reciprocatingly extruded alloy increase by 258.3%,397.5%,and 18 times,respectively.It is concluded that reciprocating extrusion can substantially improve the properties of the as-cast Mg-6.4Zn-1.1 Y alloy,particularly for elongation.The high performance of the Mg-6.4Zn-1.1 Y alloy after reciprocating extrusion can be attributed to dispersion strengthening and grain-refined microstructures.
