Electronic Structures and Alloying Behaviors of Ferrite Phases in High Co-Ni Secondary Hardened Martensitic Steels

The electronic structure of ferrite (tempered martensite phase) in high Co-Ni secondary hardened martensitic steel has been investigated. The local density of states (LOOS) of alloying elements in the steel displays the relationship between solid solubility and the shape of the LDOS. The bond order integral (BOI) between atoms in the steel shows that the directional bonding of the p orbital of Si or C leads to the brittleness of the steel. At last, ΣBOI between atoms demonstrate that C, Co, Mn, Cr, Mo, Si strengthen the alloyed steel through solid-solution effects.

Electrodeposition of Ni-Co-Fe_2O_3 composite coatings

Ni-Co-Fe2O3 composite coatings were electrodeposited using cetyltrimethylammonium bromide(CTAB)-modified Watt's nickel bath with Fe2O3 particles dispersed in it.The effects of the plating parameters on the chemical composition,structural and morphological characteristics of the electrodeposited Ni-Co-Fe2O3 composite coatings were investigated by energy dispersive X-ray(EDS) spectroscopy,X-ray diffractometry(XRD) and scanning electron microscopy(SEM).The results reveal that Fe2O3 particles can be codeposited in the Ni-Co matrix.The codeposition of Fe2O3 particles with Ni-Co is favoured at high Fe2O3 particle concentration and medium stirring,and the deposition of Co is favoured at high concentration of CTAB.Moreover,the study of the textural perfection of the deposits reveals that the presence of particles leads to the worsening of the quality of the observed <220> preferred orientation.Composites with high concentration of embedded particles exhibit a preferred crystal orientation of <111>.The more the embedded Fe2O3 particles in the metallic matrix,the smaller the sizes of the crystallite for the composite deposits.

Co-deposition of Co-Ni alloys and their microstructure analysis by PoSAP

PULSED-co-electrodeposition （PCD） is a new and promising technique for producing alloymaterials of nanometer grain size. In this letter, Co-Ni alloys were produced by PCD, and theeffect of CO+2 ion concentration in the depositing baths on the Co content and the microstruc-ture in the corresponding deposit was studied by the position sensitive atom probe （PoSAP）,TEM and X-ray diffraction. The Co-Ni phase diagram shows that, at room temperature,there are two phases in Co-Ni alloys, one is εCo with hcp lattice, the other is αCo of fcc lat-tice. A Co-Ni alloy with a Ni content below 27% consists of single εCo, beyond 36% consistsof single αCo, in between consists of εCo + αCo. The examination results of TEM, SEM andX-ray diffraction indicated that the Co-Ni deposits with average grain size of 70 nm and thick-

A new model to describe composition and temperature dependence of thermal conductivity for solution phases in binary alloys

Modelling temperature-and composition-dependent thermal conductivity in alloys is challengeable and is seldom studied systematically.In the present work,a new model is developed to describe the temperature and concentration dependence of thermal conductivity for binary alloys.In this new model,firstly thermal conductivity of pure metals was modelled as the function of temperature for each phase and each magnetic state by the corresponding physically sound model.Secondly,in order to describe the composition and temperature dependence of thermal conductivity for solid phases,the combination of the theories of Nordheim and Mott for electric conductivity of alloys with the Wiedemann-Franz law was performed.Thirdly,the reliability of the new model was verified by presently measured thermal conductivities for pure Co,Ni and Co-Ni alloys at 300,600,900 and 1100 K as well as for binary Al-Zn,Mg-Zn and U-Zr systems using the data taken from the literature.The calculated thermal conductivities can well reproduce the measured ones in one-phase regions of a series of Co-Ni alloys.The thermal conductivity in a two-phase region of the Co-Ni system is reasonably predicted as well.It is demonstrated that the new model can be utilized to evaluate the thermal conductivity over the whole investigated composition and temperature ranges for the first time and is expected to be extended to ternary and multicomponent systems by CALPHAD method,which contributes significantly to the development of computational design of materials.