Abstract
The properties of metal matrix composites (MMCs) can be optimized effectively through adjusting the type or the volume fraction of reinforcement. Generally, the coefficient of thermal expansion (CTE) of MMCs can be reduced by increasing the volume fraction of the reinforcement with lower CTE than metal matrix. However, it is great challenge to fabricate low CTE MMCs with low reinforcement volume fraction because of the limitation of reinforcement CTEs. SrxBa1−xTiO3 (SBT) powder presents negative thermal expansion behavior during the phase transformation from tetragonal to cubic phase. Here, we demonstrate that the phase transformation of SBT can be utilized to reduce and design the thermal expansion properties of SBT particle-reinforced Cu (SBT/Cu) composite, and ultralow CTE can be obtained in SBT/Cu composite. The X-ray diffraction analysis on heating indicates that the temperature range of phase transformation is extended greatly, therefore, the low CTE can be achieved within wide temperature range. Landau-Devonshire theory study on the phase transformation behaviors of SBT particles in the composite indicates that thermal mismatch stress significantly affects the Curie temperature of SBT particles and the CTE of the composite. The results given in the present study provide a new approach to design the MMCs with low CTE.
Highlights
Metal matrix composites (MMCs) have been intensively studied in the past few decades because of their excellent adjustable thermalphysics properties, such as a low coefficient of thermal expansion (CTE) and high thermal conductivity (TC)[1,2]
It is convenient method to utilize ceramic reinforcement with a low or negative CTE to reduce the ceramic volume fraction in Ceramic/Cu composite, and a low CTE and high TC can be simultaneously obtained for the composite
The X-ray diffraction (XRD) spectra indicate that no interfacial reaction and other impurities were introduced during the spark plasma sintering(SPS) process
Summary
Because Tm is higher than TC of the 20SBT powders, the Curie temperatures of some 20SBT particles in the composite increase upon heating This is different from the behavior upon cooling and will be analyzed later in this paper. The phase transformation of the SBT powders in the composite occurs over a wide temperature range owing to the inhomogeneous stress in different SBT particles, resulting in a low CTE for the composites over a wide temperature range. P and TC can be determined by as follows:
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