The majority of industrial aluminum casting alloys exhibit low thermal conductivity,which is insufficient for effective heat transfer in electronic devices.The objective of this investigation was to develop new alumin...The majority of industrial aluminum casting alloys exhibit low thermal conductivity,which is insufficient for effective heat transfer in electronic devices.The objective of this investigation was to develop new aluminum casting alloys with high thermal conductivity.The impact of alloying elements on the thermal conductivity of pure aluminum was examined,and the relationships among microstructure,thermal conductivity,and the mechanical and corrosion properties of Al-Zn-Ca-(Cu,Mg)alloys were explored.The findings indicate that in the as-cast state,the structure of the alloys consists ofα-Al and a eutectic containing the(Al,Zn)4Ca phase.Following the solution heat treatment,the(Al,Zn)4Ca phase is spheroidised,and thermal conductivity of the alloys increases,reaching over 75%that of pure aluminum.However,the heat-treated alloys exhibit low mechanical properties:tensile yield strength<60 MPa,ultimate tensile strength<160 MPa,and elongation at fracture>15%.The alloys demonstrate satisfactory fluidity and low hot tearing susceptibility.With the exception of the alloy containing copper,the alloys exhibit low corrosion rates,estimated at approximately 0.02 mm/a.展开更多
Complex studies of new Mg-Zn-Y-Zr system alloys have been carried out.The content range for the formation of the two-phase structure MgSS(Mg solid solution)+LPSO(long-period stacking ordered)in alloys of the Mg-Zn-Y-Z...Complex studies of new Mg-Zn-Y-Zr system alloys have been carried out.The content range for the formation of the two-phase structure MgSS(Mg solid solution)+LPSO(long-period stacking ordered)in alloys of the Mg-Zn-Y-Zr system was determined by thermodynamic calculations.The effect of heat treatment regimes on microstructure,mechanical,and corrosion properties was invest-igated.The fluidity,hot tearing tendency,and ignition temperature of the alloys were determined.The best combination of castability,mechanical,and corrosion properties was found for the Mg-2.4Zn-4Y-0.8Zr alloy.The alloys studied are superior to their industrial counterparts in terms of technological properties,while maintain high corrosion and mechanical properties.The increased level of pro-perties is achieved by a suitable heat treatment regime that provides a complete transformation of the 18R to 14H modification of the LPSO phase.展开更多
The Mg–Zn–Y–Zr alloys with long-period stacking-ordered(LPSO)and W eutectic phases were investigated to develop new magnesium casting alloys.The temperatures for T6 heat treatment were selected based on the hardnes...The Mg–Zn–Y–Zr alloys with long-period stacking-ordered(LPSO)and W eutectic phases were investigated to develop new magnesium casting alloys.The temperatures for T6 heat treatment were selected based on the hardness and electrical conductivity measurements.The hot tearing susceptibility of the alloys with LPSO phase is lower than that of the alloys with W phase,which is associated with the freezing range of the alloys.However,the investigated alloys displayed the same fluidity.Under T6 conditions,increasing the Y content in the alloys resulted in increased yield strength,whereas other tensile properties were similar for the alloys.The corrosion resistance was higher for the alloys with LPSO phase compared to that of the alloys with W phase.Mg−2.5Zn−3.7Y−0.3Zr(mass fraction,%)alloy with LPSO phase possessed high castability and mechanical properties,with a corrosion rate of 2 mm/year.展开更多
The microstructure formation and strengthening of an Al-5 wt.%TiO2 composites with additions of 5 wt.%Cu and 2 wt.% stearic acid(as a process control agent, PCA) during mechanical alloying and subsequent thermal expos...The microstructure formation and strengthening of an Al-5 wt.%TiO2 composites with additions of 5 wt.%Cu and 2 wt.% stearic acid(as a process control agent, PCA) during mechanical alloying and subsequent thermal exposure were studied. The powder composites were prepared by high-energy ball milling for up to 10 h. Single line tracks of the powders were laser melted. Optical and scanning electron microscopy, XRD analysis and differential scanning calorimetry were used to study microstructural evolution. The results showed that the Cu addition promotes an effective mechanical alloying of aluminum with Ti O2 from the start of milling, resulting in higher microhardness(up to HV 290), while the PCA, on the contrary, postpones this process. In both cases, the composite granules with uniform distribution of Ti O2 particles were formed. Subsequent heating of mechanically alloyed materials causes the activation of an exothermic reaction of Ti O2 reduction with aluminum, the start temperature of which, in the case of Cu addition,shifts to lower values, that is, the transformation begins in the solid state. Besides, the Cu-added material after laser melting demonstrates a more dispersed and uniform structure which positively affects its microhardness.展开更多
This work studied the effects of adding Zr and Mn in amounts less than 1wt%on the microstructure,mechanical properties,casting properties,and corrosion resistance of Mg-Zn-Cu alloys containing 2.5wt%Cu and 2.5wt%-6.5w...This work studied the effects of adding Zr and Mn in amounts less than 1wt%on the microstructure,mechanical properties,casting properties,and corrosion resistance of Mg-Zn-Cu alloys containing 2.5wt%Cu and 2.5wt%-6.5wt%Zn.The hardness and electrical conductivity measurements were used to find an optimal heat treatment schedule with the best mechanical properties.It has been established that Zr significantly increases the yield strength of the alloys due to a strong grain refinement effect.However,the presence of Mn and Zr has a detrimental effect on alloy’s elongation at fracture.It was shown that the precipitation of the Mg_(2)Cu cathodic phase in the alloy structure negatively affects the corrosion behavior.Nevertheless,the addition of Mn decreases the corrosion rate of the investigated alloys.The best combination of the mechanical,casting,and corrosion properties were achieved in the alloys containing 2.5wt%Cu and 5wt%Zn.However,the Mn or Zr addition can improve the properties of the alloys;for example,the addition of Mn or Zr increases the fluidity of the alloys.展开更多
基金supported by the Russian Science Foundation(No.24-29-00682,https://rscf.ru/project/24-29-00682/).
文摘The majority of industrial aluminum casting alloys exhibit low thermal conductivity,which is insufficient for effective heat transfer in electronic devices.The objective of this investigation was to develop new aluminum casting alloys with high thermal conductivity.The impact of alloying elements on the thermal conductivity of pure aluminum was examined,and the relationships among microstructure,thermal conductivity,and the mechanical and corrosion properties of Al-Zn-Ca-(Cu,Mg)alloys were explored.The findings indicate that in the as-cast state,the structure of the alloys consists ofα-Al and a eutectic containing the(Al,Zn)4Ca phase.Following the solution heat treatment,the(Al,Zn)4Ca phase is spheroidised,and thermal conductivity of the alloys increases,reaching over 75%that of pure aluminum.However,the heat-treated alloys exhibit low mechanical properties:tensile yield strength<60 MPa,ultimate tensile strength<160 MPa,and elongation at fracture>15%.The alloys demonstrate satisfactory fluidity and low hot tearing susceptibility.With the exception of the alloy containing copper,the alloys exhibit low corrosion rates,estimated at approximately 0.02 mm/a.
基金the Ministry of Science and Higher Education of the Russian Federation for financial support under the Megagrant(No.075-15-2022-1133)by the Strategic Academic Leadership Program“Priority 2030”(No.K2-2022-001)For the sample preparation and TEM investigation,the authors thank the Collective Use Equipment Center“Material Science and Metallurgy”for the equipment modernization program represented by the Ministry of Higher Education and Science of Russian Federation(No.075-15-2021-696).
文摘Complex studies of new Mg-Zn-Y-Zr system alloys have been carried out.The content range for the formation of the two-phase structure MgSS(Mg solid solution)+LPSO(long-period stacking ordered)in alloys of the Mg-Zn-Y-Zr system was determined by thermodynamic calculations.The effect of heat treatment regimes on microstructure,mechanical,and corrosion properties was invest-igated.The fluidity,hot tearing tendency,and ignition temperature of the alloys were determined.The best combination of castability,mechanical,and corrosion properties was found for the Mg-2.4Zn-4Y-0.8Zr alloy.The alloys studied are superior to their industrial counterparts in terms of technological properties,while maintain high corrosion and mechanical properties.The increased level of pro-perties is achieved by a suitable heat treatment regime that provides a complete transformation of the 18R to 14H modification of the LPSO phase.
基金the Ministry of Science and Higher Education of the Russian Federation in the framework of Increase Competitiveness Program of NUST«MISiS»(No.К2-2020-025),implemented by a governmental decree dated 16th of March 2013,N 211.
文摘The Mg–Zn–Y–Zr alloys with long-period stacking-ordered(LPSO)and W eutectic phases were investigated to develop new magnesium casting alloys.The temperatures for T6 heat treatment were selected based on the hardness and electrical conductivity measurements.The hot tearing susceptibility of the alloys with LPSO phase is lower than that of the alloys with W phase,which is associated with the freezing range of the alloys.However,the investigated alloys displayed the same fluidity.Under T6 conditions,increasing the Y content in the alloys resulted in increased yield strength,whereas other tensile properties were similar for the alloys.The corrosion resistance was higher for the alloys with LPSO phase compared to that of the alloys with W phase.Mg−2.5Zn−3.7Y−0.3Zr(mass fraction,%)alloy with LPSO phase possessed high castability and mechanical properties,with a corrosion rate of 2 mm/year.
基金the Ministry of Education and Science of the Russian Federation in the framework of the State Assignment to the Universities(Project No.11.7172.2017/8.9).
文摘The microstructure formation and strengthening of an Al-5 wt.%TiO2 composites with additions of 5 wt.%Cu and 2 wt.% stearic acid(as a process control agent, PCA) during mechanical alloying and subsequent thermal exposure were studied. The powder composites were prepared by high-energy ball milling for up to 10 h. Single line tracks of the powders were laser melted. Optical and scanning electron microscopy, XRD analysis and differential scanning calorimetry were used to study microstructural evolution. The results showed that the Cu addition promotes an effective mechanical alloying of aluminum with Ti O2 from the start of milling, resulting in higher microhardness(up to HV 290), while the PCA, on the contrary, postpones this process. In both cases, the composite granules with uniform distribution of Ti O2 particles were formed. Subsequent heating of mechanically alloyed materials causes the activation of an exothermic reaction of Ti O2 reduction with aluminum, the start temperature of which, in the case of Cu addition,shifts to lower values, that is, the transformation begins in the solid state. Besides, the Cu-added material after laser melting demonstrates a more dispersed and uniform structure which positively affects its microhardness.
基金financial support form the Ministry of Science and Higher Education of the Russian Federation in the framework of MegaGrant(No.220-7868-7477)。
文摘This work studied the effects of adding Zr and Mn in amounts less than 1wt%on the microstructure,mechanical properties,casting properties,and corrosion resistance of Mg-Zn-Cu alloys containing 2.5wt%Cu and 2.5wt%-6.5wt%Zn.The hardness and electrical conductivity measurements were used to find an optimal heat treatment schedule with the best mechanical properties.It has been established that Zr significantly increases the yield strength of the alloys due to a strong grain refinement effect.However,the presence of Mn and Zr has a detrimental effect on alloy’s elongation at fracture.It was shown that the precipitation of the Mg_(2)Cu cathodic phase in the alloy structure negatively affects the corrosion behavior.Nevertheless,the addition of Mn decreases the corrosion rate of the investigated alloys.The best combination of the mechanical,casting,and corrosion properties were achieved in the alloys containing 2.5wt%Cu and 5wt%Zn.However,the Mn or Zr addition can improve the properties of the alloys;for example,the addition of Mn or Zr increases the fluidity of the alloys.
