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The metallic element Mo has almost no solid solubility in copper and can be used as a nucleation particle to refine the grain size and increase the recrystallization temperature of the alloy during solidification. It is expected to obtain copper alloys with good comprehensive properties by reasonably controlling the addition amount of Mo. However, it is difficult to prepare Cu–Mo alloys with uniform structure and there are few related literatures. In this paper, the aluminothermic reaction method, which has the advantages of simple process, low cost, and large size of the prepared alloy, was adopted, and a cluster model with the atomic ratio of Mo and Ni of 1:12 was introduced to design the alloy composition. Here, five alloys with different copper contents were prepared and followed by room temperature rolling with 40%, 60%, and 80% deformation. The results show that the as-cast Cu–Ni–Mo alloys exhibit good formability, have no macroscopic defects and present a small amount of precipitates. With the increase of alloy elements Ni and Mo, the hardness and strength of the alloys increase obviously, while the electrical conductivity decreases gradually. For the rolled alloys, a large number of lamellar deformed structures are formed, the grains are obviously refined, the precipitated phases are broken and the distribution is more uniform, thus the strength and hardness of the alloy increase significantly, the plasticity decrease significantly, while the conductivity changed little. In this study, high-strength samples were obtained, which may be a valuable exploration for the preparation of Cu–Ni–Mo alloy sheets with excellent microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

Deformation-based friction rolling additive manufacturing (FRAM) is a promising solid-state additive manufacturing (AM) approach for producing non-fusible, weldable Al Li alloys. Along with the thermal cycles of conventional AM methods, the materials deposited during FRAM are affected by the repeated force of a tool head. However, the effect of repeated thermal–mechanical cycles on the microstructure and mechanical properties of a deposited material remains unclear. This study attempts to develop mechanisms by characterizing the microstructure and local mechanical properties of FRAM-ed Al Li alloys, with different deposition heights and those that underwent a different number of thermal–mechanical cycles. A recrystallized microstructure is successfully obtained and fine equiaxed grains are observed in the deposited material without pores and cracks. The value of ultimate tensile strength (UTS) reaches 98–91% of the base metal from the top to bottom regions. Under repeated thermal–mechanical cycles (from the top to bottom region), the grain size increases from 2.0 μm to 6.5 μm. The texture strength and diameter of δ' precipitate also increase, while the volume fraction decreases. Together, they lead to a decrease in local UTS and elongation, from 450.7 MPa to 415.1 MPa and from 10.4% to 6.3%, respectively. The relationship between thermal–mechanical cycles and microstructure established in this study provides the foundation for subsequent research on FRAM thermal balance and microstructure regulation. • UTS of the deposited material reached >91% of the Al Li alloy using deformation-based AM technology. • A non-planar connection interface with refine-equiaxed grains (2.0 μm) was formed between two adjacent layers. • The distribution and variation characteristics of microstructure under repeated thermal–mechanical cycles were investigated. • The relationship between the microstructure and mechanical properties was established. [ABSTRACT FROM AUTHOR]

Abstract Compound casting was performed to investigate the bonding of the molten A356 aluminum alloy cast onto the SiC p /8009Al composite that was preheated at 395–450 °C. The bonding strength was measured by carrying out a tensile test. The interfacial microstructures were characterized by scanning electron microscopy, energy dispersive spectroscope, X-ray diffraction and electron backscattered diffraction. The results showed that the bonding strength increased by 37% when the preheating temperature increased from 395 °C to 420 °C, and decreased by 6.8% as the preheating temperature further increased to 450 °C. A transition zone where the Al 4.5 FeSi phases were distributed was formed. The grain size of the Al 4.5 FeSi phase increased while its density decreased from the SiC p /8009Al composite to A356 aluminum alloy. The transition zone widened from 1350 μm to 3200 μm as the preheating temperature increased from 395 °C to 450 °C. In addition, at the preheating temperature of 450 °C, the fracture position changed from the interface between the A356 aluminum alloy and transition zone (at the preheating temperature of 395 °C and 420 °C) to the interior of the transition zone. The interface formation mechanism and its effect on the fracture mechanism were also discussed. [ABSTRACT FROM AUTHOR]

In this paper, a novel flat-top laser-aided cold metal transfer additive manufacturing (F-LCAM) method is proposed for titanium alloys to restrict internal defects and anisotropy of mechanical properties in large-scale additive-manufactured titanium structures. The proposed method uses a flat-top laser to stabilise the drifting cathode spot and suppress the irregular shape of the weld deposit by promoting thermionic emission on the molten pool surface. Compared to the cold metal transfer additive manufacturing (CMT-AM) process, the auxiliary flat-top laser promotes the wettability of the molten pool and increases the contact angle of deposition from 95° to 142° in an F-LCAM sample. The non-destructive X-ray testing (NDT) results of multi-bead multilayer deposition showed that the defects caused by the pool weld bead morphology were effectively suppressed. Attributed to fluid flow in the melt pool enhanced by the flat-top laser, the dendritic arms were broken, columnar β grains in the F-LCAM sample were finer than in CMT-AM sample, and the aspect ratios of prior-β grains decreased from approximately 6 to 1. The F-LCAM sample exhibited a higher elongation and lower anisotropy than the CMT-AM sample. Defects were observed on the fracture surfaces of the CMT-AM vertical samples, which reduced the elongation of the CMT-AM samples to lower than that of the F-LCAM sample. The ultimate tensile strength, yield strength, and elongation of the multi-bead multilayer deposition met the standards of as-forged Ti6321 titanium alloy, indicating that the Ti6321 titanium alloy structure fabricated by the F-LCAM process has acceptable tensile properties for engineering applications. [Display omitted] • A novel flat-top laser was introduced in cold metal transfer additive manufacturing (CMT-AM) process for titanium alloys. • The flat-top laser could stabilise the drifting arc cathode spot and suppress the irregular shape of the weld deposit. • Due to the flat-top laser, Marangoni flow was significantly enhanced, and the wettability of the molten pool was promoted. • The internal defects were effectively eliminated and coarse columnar grains were refined in the F-LCAM samples. • The tensile properties of F-LCAM samples met the standards of as-forged Ti6321 titanium alloy for engineering applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • More heat was generated using wire, resulting in a more uniform temperature distribution. • More deformation was generated using wire, resulting in a more significant grain refinement. • The gap between the two wires was filled with plasticization material, forming a dense and defect-free zone. • Regardless of utilizing strip or wire, a dense layer formed beneath the tool head, which leads to little difference in their mechanical properties. Friction rolling additive manufacturing (FRAM) is a solid-state additive manufacturing method capable of accommodating a wide range of material forms. However, there is a lack of comprehensive research on the optimal feedstock form. Thus, this study investigated the influence of feedstock shape on material formation, microstructure, and mechanical properties. The results revealed that irrespective of whether a strip or wire was used, the plasticized material flowed through a thin plastic flow channel (approximately 112 μm) between the tool head and the feedstock. Wire feedstock resulted in greater deformation and more significant grain refinement than strip feedstock, with grain refinements of 95 % and 81 %, respectively. Additionally, gaps between multiple wires were filled with plasticized material, forming a dense and defect-free mixing zone. Moreover, the tensile performances of the deposited samples obtained from wire and strip feedstocks exhibited no significant differences, measuring 143.9 MPa and 144.5 MPa, respectively. Numerical simulations were employed to elucidate the underlying mechanism of the temperature field and material flow behavior when strips and wires were used as feed materials. The findings of this study are anticipated to serve as a reference for selecting feedstock forms for FRAM. [ABSTRACT FROM AUTHOR]