1.IntroductionMedium Mn steel was developed be-cause the wear resistance of Hadfield steel(Mn13)is poor under low or medium im-pact and extrusion abrasion[1-4].In theforegoing investigations[2-4]we found thatwith the ...1.IntroductionMedium Mn steel was developed be-cause the wear resistance of Hadfield steel(Mn13)is poor under low or medium im-pact and extrusion abrasion[1-4].In theforegoing investigations[2-4]we found thatwith the increase of C content,theneedle-like and network carbide in mediumMn steel increased(as shown in Fig.1(a)and(c)).Although its wear resistance was largelyimproved,its impact toughness was greatlydecreased.In order to increase toughness,along-term high temperature heat-treatmentwas needed.But the treatment caused cracks展开更多
The thermal stability and glass-forming ability of Y56-xCexCo20Al24(x=15,20,25,28,38,41,44)bulk metallic glasses with a diameter of 5 mm were investigated by differential scanning calorimetry and X-ray diffraction.The...The thermal stability and glass-forming ability of Y56-xCexCo20Al24(x=15,20,25,28,38,41,44)bulk metallic glasses with a diameter of 5 mm were investigated by differential scanning calorimetry and X-ray diffraction.The results show that the thermal stability of the alloys decreases with the addition of Ce.It has the best glass-forming ability when x=25,whose calculated values can reach about 30 mm in diameter.The effect of Ce element could be explained on the view of Miedema’s theory and elec-tronegativity difference of amorphous alloys.展开更多
We report the results of dc resistivity, ac susceptibility, and thermopower study of partial substitution at Y (A site by Ca) and at Cu (B site by Ni) polycrystalline superconductors. The iodometric analysis reveals t...We report the results of dc resistivity, ac susceptibility, and thermopower study of partial substitution at Y (A site by Ca) and at Cu (B site by Ni) polycrystalline superconductors. The iodometric analysis reveals that the oxygen deficiency,δ,for YBa2Cu3O7-δ(S-I),Y0.9Ca0.1 Ba2Cu3O7-δ(S-II),Y0.8Ca0.2Ba2Cu3O7-δ(S-III) and Y0.9Ca0.1 Ba2(Cu0.99Ni0.01)3O7-δ(S-IV) samples are 0.16, 0.30, 0.39 and 0.29 respectively. The x-ray powder diffraction pattern indicates that all samples are in orthorhombic phase. The dc resistivity, ac susceptiblity and the thermopower measurements shows that the divalent Calcium doping at the trivalent Y site and transition metal Ni doping at Cu site causes a suppression of the superconducting transition temperature (Tc) from 89 to 81 K. The ac susceptibility confirms the ferromagnetic to antiferromagnetic phases at a defined Tc. The room temperature S value increases for Ca substituted YBa2Cu3O7-δwhile to that it decreases for Y0.9Ca0.1Ba2(Cu0.99Ni0.01)3O6.71. The above feature is an indicative of enhanced number of mobile holes for the Ca doped YBa2Cu3O7-δ, while to that the charge carrier density is reduced in simultaneous A (Ca) and B (Ni) site doped sample.展开更多
文摘1.IntroductionMedium Mn steel was developed be-cause the wear resistance of Hadfield steel(Mn13)is poor under low or medium im-pact and extrusion abrasion[1-4].In theforegoing investigations[2-4]we found thatwith the increase of C content,theneedle-like and network carbide in mediumMn steel increased(as shown in Fig.1(a)and(c)).Although its wear resistance was largelyimproved,its impact toughness was greatlydecreased.In order to increase toughness,along-term high temperature heat-treatmentwas needed.But the treatment caused cracks
基金This work was financially supported by the National Natural Science Foundation of China(No.50201009).
文摘The thermal stability and glass-forming ability of Y56-xCexCo20Al24(x=15,20,25,28,38,41,44)bulk metallic glasses with a diameter of 5 mm were investigated by differential scanning calorimetry and X-ray diffraction.The results show that the thermal stability of the alloys decreases with the addition of Ce.It has the best glass-forming ability when x=25,whose calculated values can reach about 30 mm in diameter.The effect of Ce element could be explained on the view of Miedema’s theory and elec-tronegativity difference of amorphous alloys.
文摘We report the results of dc resistivity, ac susceptibility, and thermopower study of partial substitution at Y (A site by Ca) and at Cu (B site by Ni) polycrystalline superconductors. The iodometric analysis reveals that the oxygen deficiency,δ,for YBa2Cu3O7-δ(S-I),Y0.9Ca0.1 Ba2Cu3O7-δ(S-II),Y0.8Ca0.2Ba2Cu3O7-δ(S-III) and Y0.9Ca0.1 Ba2(Cu0.99Ni0.01)3O7-δ(S-IV) samples are 0.16, 0.30, 0.39 and 0.29 respectively. The x-ray powder diffraction pattern indicates that all samples are in orthorhombic phase. The dc resistivity, ac susceptiblity and the thermopower measurements shows that the divalent Calcium doping at the trivalent Y site and transition metal Ni doping at Cu site causes a suppression of the superconducting transition temperature (Tc) from 89 to 81 K. The ac susceptibility confirms the ferromagnetic to antiferromagnetic phases at a defined Tc. The room temperature S value increases for Ca substituted YBa2Cu3O7-δwhile to that it decreases for Y0.9Ca0.1Ba2(Cu0.99Ni0.01)3O6.71. The above feature is an indicative of enhanced number of mobile holes for the Ca doped YBa2Cu3O7-δ, while to that the charge carrier density is reduced in simultaneous A (Ca) and B (Ni) site doped sample.
