SiCw/Al-18Si composites were prepared by squeeze casting technique.Solidification behavior of SiCw/Al-18Si composites was studied by differential scanning calorimeter(DSC) and scanning electron microscopy(SEM).The re-...SiCw/Al-18Si composites were prepared by squeeze casting technique.Solidification behavior of SiCw/Al-18Si composites was studied by differential scanning calorimeter(DSC) and scanning electron microscopy(SEM).The re-melting temperature has little effect on the solidification behavior and microstructure of composites.With the increase of SiC whisker content,onset and peak temperatures of primary Si decrease and the average size of primary silicon becomes smaller and smaller.Sr addition lowers onset and peak temperatures of primary Si,however,onset and peak temperatures of eutectic were barely affected by Sr addition.The average sizes of primary Si and Al-Si eutectic both decrease by Sr addition.展开更多
By adding different amounts of Ti into the electromagnetic stirred Al-18wt.%Mg_(2)Si alloy,the effect of Ti element on the microstructure and mechanical properties of the alloy was studied.The experimental results sho...By adding different amounts of Ti into the electromagnetic stirred Al-18wt.%Mg_(2)Si alloy,the effect of Ti element on the microstructure and mechanical properties of the alloy was studied.The experimental results show that the microstructure is refined after modification with Ti,which is related to the heterogeneous nucleation of TiAl_(3) particles on theα-Al matrix.With the increase of Ti content and holding time after stirring,the primary Mg_(2)Si phase is refined firstly and then coarsened,and correspondingly,the mechanical properties of the alloy show a trend of increasing at first and then decreasing.When the addition of Ti is 0.5wt.%and the holding time is about 20 min,the refinement effect of primary Mg_(2)Si phase is the most significant and the mechanical properties of the alloy are optimal.展开更多
The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and...The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.展开更多
The cyclic semi-solid heat treatment represents a promising technique for improving microstructure and mechanical properties of a wide range of metallic alloys. In the current research the influence of cyclic semi-sol...The cyclic semi-solid heat treatment represents a promising technique for improving microstructure and mechanical properties of a wide range of metallic alloys. In the current research the influence of cyclic semi-solid heat treatment on microstructure of Al-18% Si alloy containing 0.8% Fe has been studied. All specimens were heated in an electrically heated resistance furnace with heating rate of 10°C·min-1 to 585°C. For a complete one cycle heat treatment (5 min heating time), samples after 5 min holding at 585°C were cooled to a temperature of 550°C in still air cooling and the samples were taken out immediately for water quenching. It was found that heat treatment cycles should be limited to 3 cycles or less in order to maintain fine grain size and globular structure without agglomeration and coalescence. Cyclic semi-solid heat treatment changes morphology of iron-rich intermetallics phases to be plate-like and fine plate iron-rich intermetallics phases, in stead of needle-like iron-rich intermetallics phases that are observed in as-cast samples. Cyclic heating shows a relatively higher hardness for all heating cycles compared with as-cast one due to its finer and globular structure. Cyclic semi-solid heat treatment technique results in lower coarsening rate constant compared with isothermal heat treatment one due to coarsening discontinuous effect.展开更多
文摘SiCw/Al-18Si composites were prepared by squeeze casting technique.Solidification behavior of SiCw/Al-18Si composites was studied by differential scanning calorimeter(DSC) and scanning electron microscopy(SEM).The re-melting temperature has little effect on the solidification behavior and microstructure of composites.With the increase of SiC whisker content,onset and peak temperatures of primary Si decrease and the average size of primary silicon becomes smaller and smaller.Sr addition lowers onset and peak temperatures of primary Si,however,onset and peak temperatures of eutectic were barely affected by Sr addition.The average sizes of primary Si and Al-Si eutectic both decrease by Sr addition.
基金financially supported by the Science and Technology Development Program of Shouguang(No.2019JH14)the Science and Technology Development Program of Weifang(No.2021GX052)the Natural Science Foundation of Liaoning Province(No.080137)。
文摘By adding different amounts of Ti into the electromagnetic stirred Al-18wt.%Mg_(2)Si alloy,the effect of Ti element on the microstructure and mechanical properties of the alloy was studied.The experimental results show that the microstructure is refined after modification with Ti,which is related to the heterogeneous nucleation of TiAl_(3) particles on theα-Al matrix.With the increase of Ti content and holding time after stirring,the primary Mg_(2)Si phase is refined firstly and then coarsened,and correspondingly,the mechanical properties of the alloy show a trend of increasing at first and then decreasing.When the addition of Ti is 0.5wt.%and the holding time is about 20 min,the refinement effect of primary Mg_(2)Si phase is the most significant and the mechanical properties of the alloy are optimal.
基金Project(51274245) supported by the National Natural Science Foundation of China
文摘The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.
文摘The cyclic semi-solid heat treatment represents a promising technique for improving microstructure and mechanical properties of a wide range of metallic alloys. In the current research the influence of cyclic semi-solid heat treatment on microstructure of Al-18% Si alloy containing 0.8% Fe has been studied. All specimens were heated in an electrically heated resistance furnace with heating rate of 10°C·min-1 to 585°C. For a complete one cycle heat treatment (5 min heating time), samples after 5 min holding at 585°C were cooled to a temperature of 550°C in still air cooling and the samples were taken out immediately for water quenching. It was found that heat treatment cycles should be limited to 3 cycles or less in order to maintain fine grain size and globular structure without agglomeration and coalescence. Cyclic semi-solid heat treatment changes morphology of iron-rich intermetallics phases to be plate-like and fine plate iron-rich intermetallics phases, in stead of needle-like iron-rich intermetallics phases that are observed in as-cast samples. Cyclic heating shows a relatively higher hardness for all heating cycles compared with as-cast one due to its finer and globular structure. Cyclic semi-solid heat treatment technique results in lower coarsening rate constant compared with isothermal heat treatment one due to coarsening discontinuous effect.
