低应力热膨胀系数测试方法开发及CoCrFeNiAl_{x (x = 0, 0.5, 1)}热膨胀系数测定

Development of Low Stress Thermal Expansion Coefficient Testing Method and Determination of CoCrFeNiAl_{x (x = 0, 0.5, 1)} Thermal Expansion Coefficient

摘要: 利用放电等离子烧结炉，开发了一种在真空和低应力下测试材料线热膨胀系数的方法，并测试了高熵合金CoCrFeNiAl_{x (x = 0, 0.5, 1)} 30~800℃的平均线热膨胀系数。将圆柱形高熵合金样品放入放电等离子烧结炉的上、下压头之间，压头与试样之间的接触压强为3.1 MPa，匀速升温样品并记录系统位移，采用已知线热膨胀系数的石墨样品对单位温度内的系统位移测试值进行校正，然后计算材料的线热膨胀系数。结果表明：新开发的测试方法可以精确计算出高熵合金的平均线热膨胀系数；CoCrFeNiAl_{x (x = 0, 0.5, 1)}的线热膨胀系数介于10.0~18.9 × 10⁻⁶℃⁻¹之间，主要取决于化学成份，并且随着Al含量的增加而减小。

Abstract: A method for testing the linear thermal expansion coefficient of materials under vacuum and low stress was developed using a Spark Plasma Sintering furnace, and the average linear thermal expansion coefficient of high entropy alloy CoCrFeNiAl_{x (x = 0, 0.5, 1)} was tested at 30~800˚C. The cylindrical samples of high entropy alloy were placed between the upper and lower pressure heads in the Spark Plasma Sintering furnace, and then the samples were invariably pressed by the pressure heads with 3.1 MPa pressure and heated at constant heating speed and the system displacements were recorded. A graphite sample with known linear thermal expansion coefficient was used to correct the system displacement test values within unit temperature, and then the linear thermal expansion coefficients of the materials could be calculated. The results show that the linear thermal expansion coefficients of the high entropy alloys were accurately calculated with the newly developed testing method; the expansion coefficients of CoCrFeNiAl_{x (x = 0, 0.5, 1)} range from 10.0 to 18.9 × 10⁻⁶˚C⁻¹, mainly depending on their chemical composition, and decrease with the increase of Al content.