Design of exceptionally strong and conductive Cu alloys beyond the conventional speculation via the interfacial energy-controlled dispersion of γ-Al2O3 nanoparticles

Abstract

The development of Cu-based alloys with high-mechanical properties (strength, ductility) and electrical conductivity plays a key role over a wide range of industrial applications. Successful design of the materials, however, has been rare due to the improvement of mutually exclusive properties as conventionally speculated. In this paper, we demonstrate that these contradictory material properties can be improved simultaneously if the interfacial energies of heterogeneous interfaces are carefully controlled. We uniformly disperse γ-Al2O3 nanoparticles over Cu matrix, and then we controlled atomic level morphology of the interface γ-Al2O3//Cu by adding Ti solutes. It is shown that the Ti dramatically drives the interfacial phase transformation from very irregular to homogeneous spherical morphologies resulting in substantial enhancement of the mechanical property of Cu matrix. Furthermore, the Ti removes impurities (O and Al) in the Cu matrix by forming oxides leading to recovery of the electrical conductivity of pure Cu. We validate experimental results using TEM and EDX combined with first-principles density functional theory (DFT) calculations, which all consistently poise that our materials are suitable for industrial applications.

Synergistic strengthening effect of nanocrystalline copper reinforced with carbon nanotubes

“…However, poor mechanical performances of pure copper limit the proliferation of the metal into other fields. Although the copper matrix composite (CMC) reinforced with ceramic fibers and particulates exhibit high specific strength and specific elastic modulus over their monolithic metal, the electrical and thermal properties of the composites are usually decreased 2 3 . Comparing with ceramic reinforcements, conducting carbon nanotubes (CNTs) are competitive reinforcing materials due to their high thermal conductivity, low CTE, high damping capacity and good self-lubricant property 4 5 .…”

Effects of solute content on microstructure of nano precipitate-fine grain synergistically reinforced copper alloys

“…cuboidal and petallike) shape with sharp corners. The refining of both grain and precipitate helps improve the strength and ductility [14,15,[25][26][27], while sphere-to-angular transition strengthens the possibility of precipitate corner fracturing accompanied with an undesirable strength and ductility reduction [21][22][23]. Noteworthy to mention is that excessive alloying of Sn causes serious tin segregation and formation of brittle tin-rich phase at grain boundaries, which greatly deteriorates the overall properties of the finished product such as the decline of ductility, impact toughness and corrosion resistance [5,54].…”

“…Finer grains accommodate more dislocations [3,25], and consequently stabilise the work hardening, which is beneficial to stable plastic deformation. The spherical morphology eliminates the sharp corners in the angular precipitate and thus alleviates the strain concentration around the particle corners [21][22][23]; and the particle-matrix decohesion at smaller precipitates will occur at much higher strain due to the more coherent interface [55], all of which reduce the possibility of particle fracturing and correspondingly increase the ductility. As a whole, the reasonable alloying of Sn content is vital for optimising the microstructure and improving the mechanical properties of NPFG copper.…”

“…The precipitate size determines, to a great extent, the precipitation strengthening effect no matter caused by particle shearing [14][15][16] or Orowan looping [14,15,17] mechanisms. The morphology transformation of precipitates produces a corresponding evolution in the mechanical properties [18][19][20][21]. Specifically, the spherical shape has been suggested to eliminate the sharp corners in angular precipitates and can thereby improve the ductility by reducing the plastic strain concentration within the matrix around the precipitate corners, therefore weakening the possibility of the precipitate corner fracturing [21][22][23].…”

“…The morphology transformation of precipitates produces a corresponding evolution in the mechanical properties [18][19][20][21]. Specifically, the spherical shape has been suggested to eliminate the sharp corners in angular precipitates and can thereby improve the ductility by reducing the plastic strain concentration within the matrix around the precipitate corners, therefore weakening the possibility of the precipitate corner fracturing [21][22][23]. In this context, it is crucial to obtain an in-depth understanding of the coarsening and morphological evolution of nano-sized iron-rich precipitates in NPFG copper alloys for developing optimum alloying and process parameters and reaching optimal mechanical performance.…”