Thermal expansion behavior of MgO/Cu composite with lower MgO volume fraction

MgO/Cu composites reinforced with 1.0 vol.%, 1.5 vol.%, 2.0 vol.%, 2.5 vol.% and 3.0 vol.% MgO particles were fabricated by powder metallurgy. The effect of MgO particles on the thermal expansion behavior of MgO/Cu composites was studied, and the thermal expansion properties of MgO/Cu composites prepared were evaluated by the coefficient of thermal expansion at the temperatures range from 50 °C to 500 °C. The results show that the introduction of MgO particles significantly reduces the coefficient of thermal expansion of copper matrix. The increased temperature enhances the coefficient of thermal expansion of MgO/Cu composite, whereas more MgO content decreases the coefficient of thermal expansion of MgO/Cu composite. The thermal expansion properties of MgO/Cu composites were calculated by theoretical models. The calculated pressure values at the interface between MgO particles and copper matrix suggest that plastic deformation can occur at 350 °C, which is consistent with the variations of the measured coefficient of thermal expansion.

The graphical image shows that comparison of CTE behavior of MgO/Cu composite with different MgO particle volume percents. The increasing rate for the specimens over the temperature from 50 °C to 200 °C was much higher than that from 200 °C to 500 °C, and there was a common inflexion at temperature of 350 °C. It is generally known that a considerable amount of internal stress would be released and thermal stress be generated upon heating and cooling progresses. During heating process, the thermal stress exhibits as tensile stress on the MgO and compressive stress on the copper matrix. When heating all the specimens at the temperature among 50–200 °C, most of the residual stress generated during fabrication would be released immediately, resulting in higher CTE increasing rate.Figure optionsDownload as PowerPoint slideHighlights
► Revealed thermal expansion properties of MgOp/Cu composite.
► The thermal expansion behavior is associated with pressures at the interface.
► Variation of pressures at the interface is closely related to served temperature.
► The CTEs of composite were compared between experiment and theoretical models.