Suppression of discontinuous precipitation and strength improvement by Sc doping in Cu-6 wt%Ag alloys

In low-Ag Cu matrix alloys,the presence of coarse discontinuous precipitates may limit strength.We demonstrated that discontinuous precipitation was suppressed,and continuous precipitation was en-hanced by the doping of Cu-6 wt%Ag with Sc.A high-volume fraction of continuous precipitates,which nucleated on{111}planes,led to a 55 MPa increase in strength,with only a slight decrease in electri-cal conductivity.The addition of Sc inhibited the nucleation of discontinuous precipitates by causing the Sc and the Ag to co-segregate onto grain boundaries,thus forming a thin intermetallic compound layer between grains.After deformation,both discontinuous and continuous precipitates were drawn into Ag fibers.The combination of deformation strain and doping caused an increase in density and a decrease in the diameter of Ag fibers,resulting in about 205 MPa increase in doped samples when the deformation strain reached 4.9.The thinner,denser Ag fibers in the doped samples also caused higher electron scatter-ing at interfaces,leading to electrical conductivity that was 11%IACS lower than in non-doped samples.For reference,100%IACS(International Annealed Copper Standard)is equivalent to 1.7241μΩcm.

Magnetic properties and magnetocaloric effects of Gd65（Cu,Co,Mn）35 amorphous ribbons

The magnetic phase transition and magnetocaloric effects of Gd65(Cu,Co,Mn)35 amorphous ribbons were investigated. The increased Mn substitution for Co or Mn substitution for Cu led into a higher secondorder magnetic phase transformation temperature, near 200 K in all ribbons. Under the field change of 7T, a maximum entropy change(Sm max) of 6 J kg^-1K^-1 was achieved in Gd(65)Cu10Co20Mn5 ribbon and slightly dependent on the compositions. With varied composition, a full width at half of Sm maxwas greatly widened to be over than 180 K for Gd65Cu15Co10Mn(10) ribbon. The refrigeration capacity was also greatly enhanced to 1000J kg^-1 for Gd65Cu20Co10Mn5 ribbon, which was even excellent compared with other Gd-based amorphous systems.

Precipitation of α-Fe from Fe_(84-x)Si_(4)B_(12+x)(x=1,3) Amorphous Alloys Under High Magnetic Field Annealing

This work aims to investigate the effects of high magnetic field annealing(HMFA) on the precipitation of α-Fe from Fe_(84-x)Si_(4)B_(12+ x)( x = 1, 3) amorphous precursors. Isothermal annealing process for Fe_(81)Si_(4)B_(15) and Fe_(83)Si_(4)B_(13) amorphous ribbons has been performed with and without the magnetic field. The magnetic field shows the effects of increasing the nucleation rate and decreasing the grain size of α-Fe crystals simultaneously, during the crystallization processes of the investigated amorphous alloys. By applying HMF, α-Fe crystals with more homogeneous distribution and smaller grain size are achieved in the amorphous matrix, which is crucial helpful to improve the magnetic properties for Fe–Si–B amorphous alloys. The mechanism of HMFA affecting the crystallization microstructure is also discussed in the present work.

Synthesis of Ag-Cr thin film metallic glasses with enhanced sulfide-resistance

The thin film glass forming region of the immiscible Ag-Cr binary system was explored by combinatorial sputtering.The electrochemical behavior of Ag-Cr alloy films with different Cr content in different corrosive environments containing S^2-or Cl-were investigated in comparison with those of pure silver.The Ag-Cr thin film metallic glasses(TFMG)exhibit much enhanced corrosion resistance in 0.01 M K2S solution,comparing with that of the bulk silver,the Ag50 Cr50 TFMG exhibits much higher corrosion potential as well as two orders of magnitude lower corrosion current density.Nevertheless,no obvious improvement of the corrosion resistance can be found for the glassy films in 0.1 M NaCl solution.