Abstract
Mg_2Si (Magnesium silicide) has been expected as the materials used for thermoelectric (TE) technologies due to lightweight, abundance of its constituent elements and its non-toxicity. Because TE conversion devices are subjected to various thermo-mechanical loadings during operation, evaluation of the mechanical properties of Mg_2Si is necessary for designing reliable TE modules. Furthermore, Mg_2Si is used at 600℃ in the view of thermoelectric properties, however, the effect of heat exposure at 600 ℃ on the mechanical properties of Mg_2Si has not been sufficiently investigated. In the present study, therefore, mechanical properties of Mg_2Si after heat exposure at 600 ℃ were evaluated. The effect of holding time on the strength was also investigated. The specimen was cut from an as-sintered pellet and was polished and heated in Ar atmosphere at 600 ℃ for 100 h, 250 h, respectively. The four-point bending test was carried out on as-sintered and heat-exposed specimens to obtain bending strength at room temperature. The as-sintered specimen showed bending strength of 48 MPa on average. In case of 100 h heat-exposed specimen, the bending strength was almost equal to that of as-fabricated specimen. However, it increased after the heat exposure for 250 h up to about 90 MPa. The fracture surface observations revealed that the increase in strength is attributed to slight oxidation on the surface.
