Thermal management materials based on molybdenum (Mo) and copper (Cu): Elucidation of the rolling-induced evolution of thermo-physical properties (e.g. CTE)

• Published in: Journal of alloys and compounds Vol. 776; pp. 387 - 416
• Main Authors: Reiser, Jens, Hoffmann, Andreas, Hain, Johannes, Jäntsch, Ute, Klimenkov, Michael, Hohe, Jörg, Mrotzek, Tobias
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 05.03.2019; Elsevier BV
• Subjects: Coefficient of thermal expansion; Copper; Crystallographic texture; Crystallography; Electrical resistivity; Evolution; Heat conductivity; Heat transfer; Ingots; Liquid phases; Material properties; Modulus of elasticity; Molybdenum; Molybdenum-copper composites; Physical properties; Plastic deformation; Recrystallization; Reduction; Residual stress; Rolling; Thermal conductivity; Thermal expansion; Thermal management; Rolling; Thermal management; Thermal conductivity; Coefficient of thermal expansion; Molybdenum-copper composites; Crystallographic texture
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.10.235

This paper describes a systematic analysis of liquid-phase infiltrated molybdenum (Mo) copper (Cu) composites, deformed by various levels, and elucidates the impact of (i) the copper content, and (ii) the rolling reduction on the evolution of the material properties. The rolling-induced change of the thermo-physical properties can be traced back to (ii-a) the evolution of the geometry (viz. the flattening of the molybdenum and the copper phase during rolling) and (ii-b) the evolution of the crystallographic texture. Four infiltrated ingots with a copper content of 23, 39, 48 and 54 vol % were produced. Each ingot was gradually rolled down to a final degree of deformation of 0.5, 1, 1.5, 2 and 2.38, which corresponds to a rolling reduction of 39%, 63%, 78%, 86% and 90%. In summary, four material compositions (23, 39, 48 and 54 vol % Cu) in six conditions (as-infiltrated and five as-rolled conditions) were examined. The evolution of the microstructure is correlated with the evolution of the mechanical and thermo-physical properties such as hardness (HV2), Young's modulus, E, electrical conductivity, σ, thermal conductivity, k, and the coefficient of thermal expansion, α (CTE, in the range of 350 °C (623 K) – 750 °C (1023 K)). It was found, that the same thermal conductivity can be gained by using either a low copper-content composite that features a low degree of deformation or by using a high copper-content composite that was rolled down to a high degree of deformation. Furthermore, we were able to demonstrate that peculiarities in the CTE-over-T curves can be traced back to the plastic deformation of the copper phase, which is affected by rolling-induced residual stresses and recrystallisation processes during the CTE measurement. [Display omitted] •Four liquid-phase infiltrated MoCu ingots were produced (Cu: 23, 39, 48, 54 vol %).•The ingots were rolled down to five degrees of deformation (0.5, 1, 1.5, 2 and 2.38).•Evolution of the thermal conductivity and expansion behaviour were analysed.•Material properties = f (copper content, degree of deformation (geometry, texture)).•The peculiar expansion behaviour is caused by the plastic deformation of the Cu phase.