Thermal expansion and thermal diffusivity properties of Co-Si solid solutions and intermetallic compounds

• Length change difference between rapidly and slowly solidified Co-Si alloy occurs at high temperature.
• Generally CTE increases with an increasing Si content.
• The thermal diffusion abilities are CoSi2 > Co95Si5 > Co90Si10 > Co2Si > CoSi if T exceeds 565 K.
• All the CTE and thermal diffusivity variations with T satisfy linear or polynomial relations.

The thermal expansion of Co-Si solid solutions and intermetallic compounds was measured via dilatometric method, compared with the results of first-principles calculations, and their thermal diffusivities were investigated using laser flash method. The length changes of rapidly solidified Co-Si alloys are larger than those of slowly solidified alloys when temperature increases to around 1000 K due to the more competitive atom motion. The coefficient of thermal expansion (α) of Co-Si alloy increases with an increasing Si content, except that the coefficient of thermal expansion of Co95Si5 influenced by both metastable structure and allotropic transformation is lower than that of Co90Si10 at a higher temperature. The thermal expansion abilities of Co-Si intermetallic compounds satisfy the relationship of Co2Si > CoSi > CoSi2, and the differences of the coefficients of thermal expansion between them increase with the rise of temperature. The thermal diffusivity of CoSi2 is evidently larger than the values of other Co-Si alloys. If temperature exceeds 565 K, their thermal diffusion abilities are CoSi2 > Co95Si5 > Co90Si10 > Co2Si > CoSi. All the coefficient of thermal expansion and thermal diffusivity variations with temperature satisfy linear or polynomial relations.