Cu-Ti alloys exhibit excellent mechanical properties and high-temperature stability, and are among the environmentally friendly ultra-high strength copper alloys that can replace Cu-Be alloys. However, ultra-high-strength Cu-Ti alloys (>1000 MPa) typically suffer from low electrical conductivity (<15% IACS). To address this trade-off, this study uses the Cu-3Ti-1.2 Mg alloy established in our previous studies as the base material, coupled with a combined thermomechanical treatment consisting of aging, cold rolling, secondary aging, cold rolling, and tertiary aging. This approach achieves a synergistic enhancement in the overall alloy performance: a tensile strength of 1182 MPa, a yield strength of 1088 MPa, and an electrical conductivity of 20.04% IACS. Microstructural analysis reveals that the peak-aged alloy exhibits a microstructure characterized by high dislocation density, substructures dominated by low-angle grain boundaries and cold-deformation textures, with precipitates mainly composed of β’-Cu₄Ti, accompanied by a small amount of Cu₂Mg phase, nanoscale twins, and very few β-Cu₄Ti phases. The high strength of the alloy primarily originates from the significant precipitation strengthening induced by the strong interactions between finely dispersed β’-Cu₄Ti precipitates and dislocations within the matrix. Meanwhile, the precipitation of Ti atoms from the matrix in the form of precipitates effectively reduces electron scattering, thereby significantly improving the electrical conductivity while maintaining high strength. Furthermore, the precipitation kinetic equations established based on conductivity evolution at different temperatures, together with the constructed time-temperature-transformation (TTT) curves, indicate that the activation energy for the precipitation reaction in this alloy is 44 kJ/mol. This work aims to provide a feasible processing route and theoretical support for the development of copper alloys with ultra-high strength and high electrical conductivity.

To address the challenge of synergistically enhancing strength, ductility, and electrical conductivity in copper alloys for connector applications, this study designed Cr-content-graded (0-0.4 wt%) Cu-Ni-Co-Si-Mg-xCr alloys. Employing a two-stage cold rolling and aging treatment (50 % initial rolling + aging + 88.9 % finish rolling + Two-Stage Aging), combined with microstructural characterization (SEM/TEM/EBSD/XRD) and performance testing (hardness/elongation/electrical conductivity), we systematically investigated the effects of Cr content on aging precipitation behavior, microstructural evolution, and resultant properties. The optimal aging regime was established as 450 degrees Cx 6 h + 450 degrees Cx 8 h. Results indicate that increasing Cr content to 0.4 wt% induces a marginal strength reduction (827.6 -> 748 MPa), whereas electrical conductivity and fracture elongation exhibit substantial enhancements-increasing from 45.2 % to 56.2 %IACS and 5.6-10.0 %, respectively. The variation in strength originates from the synergistic effects of texture evolution and precipitation behavior: After cold rolling, the alloy primarily develops Brass, S, Goss, and Copper textures. Alloys with 0 % and 0.15 % Cr exhibit higher proportions of Brass and S textures, resulting in superior strength. During aging, Cr reacts with Co and Si to form Cr3Co5Si2 and Cr15Co9Si6 phases, reducing the solid-solution content of Ni, Co, and Si in the matrix. This effectively "purifies" the matrix, thereby enhancing electrical conductivity. When Cr content reaches >= 0.32 wt%, Cr serves as nucleation sites for delta-(Ni,Co)2Si phases, promoting their precipitation. However, the coarse Cr15Co9Si6 phase may act as stress concentration sites, resulting in a reduction of the alloy's strength. Moreover, Cr addition enhances alloy ductility through a synergistic mechanism: suppressing microcrack nucleation by grain size enlargement while promoting homogeneous dislocation slip via precipitate refinement.

Precipitation strengthening in engineering alloys arises from the interaction of moving dislocations with second-phase particles, yet experiments rarely separate the contributions of precipitate size, morphology, interface character, spatial distribution, and external loading. This review organizes the computational evidence using precipitate parameters as the primary axis, so that the descriptor controlling strength in a given alloy state can be identified. Evidence is surveyed from molecular dynamics (MD), discrete dislocation dynamics (DDD), phase-field modelling (PFM), and Kampmann–Wagner numerical (KWN) models across age-hardenable Al, Mg, Cu-, Ni-, Fe-base, and high-entropy alloy systems, comparing how each parameter shifts the cutting-to-bypass transition. Several mechanisms move the effective resistance away from uniform-array, single-radius estimates. Lower-tail size statistics and soft-channel percolation lower the bypass threshold, off-centre slip-plane cutting reduces local cross sections, coherency loss drives interface-mediated transformations, and modulus mismatch produces anomalous strengthening even for soft particles. Temperature and strain rate move the boundary between shearing, bypassing, and interface-mediated transformation, so that the power-law superposition exponent for combined mechanisms is state-dependent rather than a material constant. The parameter-level view points out which descriptor controls strength in a given alloy state and helps connect atomistic, mesoscale, and microstructure-evolution evidence in a common picture.

As electronic products advance toward higher integration and miniaturization, the performance demands on filament materials have increased significantly. These materials now require excellent continuous deformation processing capabilities, along with improved electrical conductivity and signal transmission stability. In response to these challenges, this study separately prepares polycrystalline copper wire and single-crystal copper wire, focusing on their distinct structural characteristics. Key microstructural aspects examined include grain morphology, recovery and recrystallization behavior, texture evolution, and twinning features. The results indicate that as the degree of deformation increases, the Schmid factor and small angle grain boundary content inside polycrystalline copper wire and single crystal copper wire decrease, while the large angle grain boundary content show an increasing trend. Moreover, this increasing trend is more pronounced in the accumulated micro wire diameter state of large deformation. Compared to polycrystalline copper wire, single crystal copper wire has a higher proportion of Schmidt factor and small angle grain boundaries. In addition, the deformation twinning structure and recovery recrystallization structure inside single crystal copper wire appear later than polycrystalline copper wire, The recovery degree of single crystal copper wire is much higher than that of polycrystalline copper wire. Due to the higher Schmid factor of <100> compared to <111>, the higher the Schmid coefficient, the stronger the deformation ability. In the state of micro-wire diameter, the main texture type of single crystal copper wire is <111> + <100>, and the main texture type of polycrystalline copper wire is <111> + <112>. Therefore, single crystal copper wire has higher deformation ability compared to polycrystalline copper wire.

This study investigates the influence of Zr addition on the microstructural evolution and mechanical properties of Cu-3Ti alloys. After peak aging at 450 °C for 1 h, the Cu-3Ti alloy exhibited a tensile strength of 936 MPa and an elongation of 7.5

To improve the plastic deformation capacity of the immiscible Cu-7Fe alloy, this study investigated the effects of Ag and Al additions on the stacking fault energy (SFE) and microstructural properties by combining first-principles calculations with experimental methods. The results demonstrate that both Ag and Al effectively modified the morphology and distribution of the second phases in the Cu-Fe alloy. Specifically, the addition of Ag eliminated coarse dendritic Fe phases, while the addition of Al promoted the spheroidization of some Fe phases. In terms of mechanical properties, the addition of Ag increased the alloy strength from 308 MPa to 318 MPa and the elongation from 30

Ag microalloying offers a potential route to regulate the cryogenic deformation response of Cu-Fe alloys, but its effect on deformation substructures and heterogeneity in the Cu matrix remains unclear. In this study, molecular dynamics simulations and multiscale microstructural characterization were combined to investigate cryorolled Cu-6.2 wt% Fe-xAg alloys with x = 0, 0.17, 0.51, and 0.85 wt%. GSFE calculations on composition-corresponding Cu-7 at% Fe-xAg model alloys show that Ag addition decreases the intrinsic stacking fault energy and increases the GSFE-derived twinnability parameter. These results suggest that Ag modifies stacking-fault-related deformation tendencies in the fcc Cu matrix. SEM/EDS and XRD results reveal a Cu-Fe dual-phase structure without detectable coarse Ag-rich phases or independent Ag diffraction peaks. EBSD analysis shows that local orientation gradients, grain-scale orientation spread, and LAGB network density vary non-monotonically with Ag content. The 0.51Ag alloy exhibits the highest mean KAM value of 0.93 degrees, the largest area fraction of regions with KAM > 1.0 degrees of 35.0%, the highest mean GOS value of 9.74 degrees, and the largest LAGB length per unit area of 1.13 mu m(-1). Texture and TEM observations further reveal a more dispersed orientation distribution, pronounced dislocation tangles, and localized defect bands in this alloy. The 0.51Ag and 0.85Ag alloys exhibit higher hardness values of 155.96 +/- 2.97 HV and 158.82 +/- 2.01 HV, respectively. Their electrical conductivities decrease to 37.85 +/- 1.64%IACS and 36.48 +/- 1.92%IACS, respectively. These results indicate that appropriate Ag microalloying, particularly 0.51 wt% Ag, facilitates defect storage, orientation distortion, and deformation substructure development during cryorolling. This provides a GSFE-guided microstructural basis for improving deformation resistance and controlling cryorolled substructures in Cu-Fe alloys.

This study investigates the effects and mechanisms of Mg addition on the microstructure, precipitation behavior, strength, and electrical conductivity of Cu-3Ti alloys. The work seeks to balance the inherent trade-off between strength and conductivity via Mg alloying combined with thermomechanical processing. A pre-aging (pre-aging + cold rolling + aging) process was applied to Cu-3Ti-xMg alloys with varying Mg contents (0, 0.3, 0.6, 1.2 wt%). Characterization techniques including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were employed to analyze the microstructural evolution and precipitation characteristics. The results indicate that Mg addition effectively refines the dendritic structure of the as-cast alloy and promotes a more uniform distribution of Ti in the matrix. After aging treatment, Mg optimizes the precipitation behavior through two synergistic mechanisms. Firstly, it promotes dislocation multiplication, which enhances the interaction between precipitates and dislocations. This results in a significant refinement of the continuous beta'-Cu4Ti precipitates, reducing their average size from 22.96 nm to 13.73 nm. Secondly, Mg increases the interplanar spacing and interfacial energy of the discontinuous beta-Cu4Ti precipitates, thereby effectively suppressing their nucleation and growth. Consequently, the content of detrimental cellular structures is markedly reduced. Furthermore, Mg addition further refines the grains, increases the proportion of low-angle grain boundaries, enhances local strain (as indicated by KAM values), and raises the overall content of cold deformation textures (Brass, Copper, S). The synergistic regulation of these multi-scale microstructural features enables the Cu-3Ti-1.2Mg alloy to achieve a strength of 1022 MPa while maintaining electrical conductivity exceeding 15%IACS. Quantitative analysis of strengthening mechanisms reveals that precipitation strengthening and dislocation strengthening are the primary contributors, and the introduction of Mg significantly enhances both. This work systematically elucidates the influence of Mg on the microstructure, properties, and precipitation behavior of Cu-3Ti alloy, providing an important theoretical foundation and practical guidance for the development of high-performance high-strength conductive Cu-Ti based alloys.

Cu-Ni-Co-Si-Mg-xCr alloys (where x = 0, 0.15, 0.32, or 0.4 wt%) were prepared, and stress relaxation tests were conducted at 50 degrees C, 100 degrees C, and 150 degrees C for 48 h. The results showed that the addition of Cr considerably enhanced the stress relaxation resistance of the Cu-Ni-Co-Si-Mg alloys at 150 degrees C. Compared with that of the 0 % Cr alloy, the stress relaxation resistance improved by 29.7 %, 22.6 %, and 23.3 % as the Cr content increased. To understand the underlying mechanisms, the microstructure of the alloys, the morphology of the precipitates, and the dislocation density before and after the stress relaxation tests were analyzed via electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The differences in precipitates and grain size were the primary reasons for the variations in stress relaxation resistance. The delta-(Ni, Co)2Si phase constitutes the main precipitate in the alloys. Adding 0.15 % Cr can produce Cr precipitates with non-coherent orientation relationship with Cu matrix, which are effective in pinning dislocations. Moreover, the addition of Cr increased the grain size, which reduced the preferential orientation of the grains and the activation of the dislocation sources during microplastic deformation. Both factors suppressed dislocation movement, which is the fundamental reason for the enhanced stress relaxation resistance of the Cu-Ni-Co-Si-Mg-0.15Cr alloy.

In this work, significant grain refinement of pure titanium (Ti) was achieved via trace yttrium (Y) addition and a series of mechanical processes. The grain refinement mechanism, static recrystallization and texture evolution of pure Ti with Y addition were studied systematically. Three mechanisms by which Y refines grains of as-cast pure Ti were revealed: heterogeneous nucleation of prior (3 grain facilitated by in-situ formed Y2O3 particles with monoclinic structure; Y2O3 particles inhibits prior (3 grain growth by pinning grain boundaries to; solute Y provides constitutional supercooling. In addition, grain refinement and randomly oriented alpha grains promoted the decreased texture density in casting materials with Y addition. After a series of thermo-mechanical treatments, the monoclinic structure of Y2O3 particles was transformed into a body-centred cubic (BCC) structure, and the grains of pure Ti, Ti-0.1Y alloy and Ti-0.5Y alloy with completely recrystallized microstructure were refined to 4.05 mu m, 2.96 mu m and 2.82 mu m, respectively. The Y2O3 particles with BCC structure effectively inhibited grain growth during recrystallization annealing. Furthermore, it was revealed that the recrystallization mechanism was mainly dominated by the synergy of discontinuous static recrystallization (DSRX) and continuous static recrystallization (CSRX) during annealing. Nano-Y2O3 particles with BCC structure inhibited CSRX and promoted DSRX, whilst coarse particles initiated the PSN recrystallization mechanism.

With the development of high-end integrated circuits toward higher integration and ultra-thin designs, the comprehensive performance requirements for Cu-Ni-Si alloys as lead frame materials continue to increase. In this paper, the microstructure of the alloy is optimized by adjusting the deformation and aging parameters during the two-stage rolling process to enhance its performance and reveal the underlying mechanism. It was found that the hardness and strength of the alloy were enhanced while the conductivity remained unchanged or even slightly improved. With an increase in two-stage rolling deformation, the dislocation density of the alloy increases, promoting the rapid precipitation of the second phase and a reduction in grain size. The improvement in strength is primarily attributed to the synergistic effects of dislocation strengthening, precipitation strengthening, and grain boundary strengthening. In addition, with an increase in deformation, the texture strength of Cube, S, and Copper gradually decreases, while that of Brass increases significantly. This texture transformation is positively correlated with the comprehensive properties of the alloy.

The effects of trace cerium (Ce) addition on the microstructural and textural evolution and the dynamic recrystallization (DRX) of the ultrahigh-purity copper (Cu) containing small amounts of sulfur (S) were investigated using a Gleeble-1500 thermal simulation tester at 600 degrees C. The results show that with increasing Ce content, the grain size of the Cu-S (S2) alloy gradually decreases and the grain boundary embrittlement induced by S impurities is considerably inhibited. The addition of Ce promotes the DRX process of the S2 alloy and changes its DRX mechanism from discontinuous to continuous and twinning-induced DRX mechanisms. The texture component and intensity of the S2 alloy vary with the increase of Ce content. The addition of 120x10-6 Ce (mass fraction) is favorable for the grain orientation randomization, which is attributed to the promoted DRX.

Cu–Ti alloy has excellent mechanical properties and high‐temperature stability. It is an ultra‐high‐strength, environmentally friendly copper alloy that serves as a substitute for Cu–Be alloys. However, high‐strength copper titanium alloy (strength > 1000 MPa) generally has low conductivity (<20% international annealed copper standard (IACS)) and poor elongation (about 6%). This study utilizes an integrated approach of aging, cold rolling, and subsequent aging to develop a Cu–3Ti alloy with a balanced combination of high strength, superior electrical conductivity, and enhanced plasticity. The alloy achieves high strength, with a tensile strength of 1043 MPa and a yield strength of 1017 MPa, while also exhibiting excellent electrical conductivity (24.13%IACS) and elongation (10%). Transmission electron microscopy analysis demonstrates that the abundant presence of β ′‐Cu 4 Ti precipitation phases, combined with dense dislocation networks in the Cu–3Ti alloy matrix, plays a crucial role in enhancing its mechanical performance. The emergence of β ′‐Cu 4 Ti phases induces Ti depletion in the copper solid solution, thereby suppressing lattice distortion‐induced carrier scattering. The dominant strengthening mechanism is identified as Orowan bypassing mechanism. Through thermodynamic analysis, a modified Johnson–Mehl–Avrami–Kolmogorov model is formulated to describe precipitation kinetics and an activation energy of Q = 60 kJ mol −1 determined via Arrhenius equation fitting.

In this study, C1720W microfilament was used to produce fuzz buttons, and their service performance was examined under mechanical compression at 125 degrees C to simulate actual operating conditions. The microstructural evolution and failure mechanisms of the C1720W microfilament fuzz buttons during service were investigated. The results show that after mechanical compression, the surface coating of the fuzz buttons began to detach and fracture. As the number of compression cycles increased, the areas of detachment and fracture expanded, causing a transition from elastic to plastic deformation, weakening the elastic recovery, and making the fuzz buttons unable to connect the circuit boards. TEM analysis revealed that before service, the fuzz buttons contained BeCo, Be2Cu, and BeCu phases. After service, the Be2Cu phase disappeared, while BeCo and BeCu phases remained. However, their interfaces changed from coherent to semi-coherent and even incoherent, leading to a performance decline. New phases, such as Co, Be, and Be12Co, appeared after service. Nano-twin phenomena were observed both before and after service, with the average nano-twin width decreasing from 21.09 nm to 8.40 nm, and the nano-twin density also decreasing. These changes may be one of the reasons for the performance decline of the C1720W microfilament fuzz buttons.

This study systematically investigated the effects of Cr, Zr and Mg additions combined with thermomechanical processing on grain refinement, precipitation behavior, electrical conductivity, and mechanical properties in CuZn-Ni-Si alloys. The addition of Cr, Zr and Mg maintains the electrical conductivity between 28.60 % IACS and 28.95 % IACS by altering solute scattering, grain boundary density, and dislocation scattering within the alloy. Increased grain boundary density and dislocation scattering partially counteracted solute purification benefits, with stable conductivity maintained through solute-defect scattering modulation. However, more importantly, a dual-phase heterostructure comprising Cr3Si and delta-Ni2Si phases was successfully introduced into the system of microalloyed materials. Thermodynamic competition drove the preferential formation of uniformly distributed Cr3Si phases, which act as heterogeneous nucleation sites to refine and disperse delta-Ni2Si precipitates during aging. The Cr3Si phase enhanced work-hardening capacity by impeding dislocation motion via the Orowan mechanism, while semi-coherent delta-Ni2Si interfaces delayed necking through dislocation storage. On this basis, the microstructural innovations enabled significant concurrent improvements in strength and plasticity. Through synergistic interactions of precipitation strengthening, dislocation strengthening, and grain refinement mechanisms under dual-phase heterogeneous microstructure, the newly developed Cu-8.75Zn-1.2Ni-0.4Si-0.25Mg-0.2Cr0.1Zr-0.1Sn (wt%) alloy demonstrated optimized mechanical properties with yield strength, tensile strength, and elongation reaching 509 MPa, 563 MPa, and 18.50 %, respectively. The optimized alloy exhibits substantial improvements in mechanical properties compared to the counterpart without Cr, Zr and Mg additions, achieving a 14.38 % enhancement in yield strength, 18.0 % increase in tensile strength, and remarkable 117.65 % elevation in elongation. These findings provide a theoretical foundation for designing advanced Cu alloy strips for highperformance connectors in new energy vehicles.

Cu-Ni-Si alloys are extensively employed across the electronics industry and diverse sectors because of their unparalleled blend of strength, electrical conductivity, and stress relaxation resistance. The Cu-Ni-Si-Co-Mg-(Cr/ Mn) alloy was prepared via the vacuum induction melting process. The effects of Cr and Mn on the microstructure and characteristics of the alloy were examined through transmission electron microscopy, electrical conductivity tests, tensile tests, and stress relaxation tests. The incorporation of Cr and Mn considerably increased the mean precipitate size within the Cu-Ni-Si-Co-Mg alloy, as evident in a comparative analysis with the control sample. For the Cu-Ni-Si-Co-Mg-(Cr/Mn) alloy, (Ni, Co)2Si was the main precipitated phase, with Cr coprecipitating as elemental Cr particles and some Cr particles together with (Ni, Co)2Si particles, whereas Mn existed in the solid solution. To elucidate the effects of Mn and Cr on the precipitated phase in the Cu-Ni-Si-CoMg-(Cr/Mn) alloy, a precipitation kinetics equation was formulated to govern the phase evolution during the aging process. The "S" curve of the isothermal phase transition kinetics was subsequently plotted. The incorporation of Cr and Mn into the Cu-Ni-Co-Si-Mg-(Cr/Mn) alloy accelerated the nucleation rate of the precipitates. The addition of Mn and Cr to the alloy negligibly affected its tensile strength and yield strength. The tensile strength exhibited a narrow variation range of 763-783 MPa. The incorporation of Mn notably enhanced the stress relaxation resistance of the alloy but slightly reduced its electrical conductivity. In contrast, the addition of Cr had a more modest positive influence on the stress relaxation resistance, yet it clearly increased the electrical conductivity by 11.9 %. Furthermore, the individual effects of Mn and Cr on the stress relaxation resistance properties of these alloys were comprehensively investigated.

This study investigates the effects of dual-stage rolling and double aging on the microstructural evolution and performance of Cu-Ni-P alloys, maintaining a total rolling reduction of 75 %. Results show that after two-stage rolling and aging, the alloy achieves optimal performance: 66.1 %IACS electrical conductivity, 213.7 HV hardness, 630 MPa ultimate tensile strength, and 616 MPa yield strength. Cold rolling promotes extensive precipitation of Ni and P within the Cu matrix, forming phases like Ni3P, Ni12P5, and Ni2P, enhancing both electrical conductivity and strength. Dual-stage rolling further refines the grain size from 3.3 mu m to 2.2 mu m, enhancing grain boundary strengthening. The study found that dislocation strengthening and aging strengthening contribute 30 % and 48 %, respectively, to the total yield strength. This work provides experimental evidence for optimizing thermomechanical treatments of Cu-Ni-P alloys, supporting performance improvements in industrial applications.

With the rapid advancement of the high-end electronic information industry, there is an increasing demand for metallic wires featuring ultra-fine diameters and high strength. Due to their superior strength and plastic deformability compared to pure copper wires, Cu-Ag alloy wires have attracted significant attention. In this study,Cu-20Ag alloy wires with various diameters were fabricated, and the evolution of their microstructure and twinning characteristics under large cumulative deformation was systematically investigated. The results show that the as-cast Cu-20Ag alloy rod exhibits a continuous eutectic network structure. As the wire diameter decreases, this network-like grain structure gradually transforms into fibrous grains. When the wire reaches the micron-scale, significant mutual diffusion between the Cu and Ag phases occurs, resulting in the formation of an abnormal interfaces induced by mechanical alloying. With further deformation, the Ag phase thickness is reduced, interdiffusion between Cu and Ag phases becomes more pronounced, and the interaction with twinning becomes increasingly significant. Moreover, cumulative deformation leads to a gradual refinement in both the twin width and twin boundaries within the Cu-20Ag wires. These findings provide theoretical insights for the development of ultrafine Cu-Ag wires and help to bridge the research gap in understanding the extreme deformation mechanisms of Cu-Ag alloys with high silver content.

Oxygen is an important strengthening element for titanium (Ti) alloys. The face-centered cubic (fcc) structure in Ti alloys attracts attention due to its formation mechanism and superior mechanical properties. This study utilized high-pressure torsion to create a nanocrystalline hexagonal close-packed (hcp) Ti matrix with fcc phase lamellae in various Ti-O alloys. We show that both oxygen content and strain can be tuned to control the formation of the fcc phase. At low oxygen concentrations, the fcc phase appears as an intergranular structure, while at higher oxygen levels, it evolves into a lath-like morphology. In addition to the hcp/fcc normal orientation relationships, a new w/fcc interface orientation of {0002}w||{220}fcc is identified. Oxygen atoms are found to preferentially distribute in fcc lamellae, which is supported by density functional theory. Energy loss near-edge structure analysis indicates that oxygen atoms become more interstitial in fcc lamellae than in the matrix. This oxygen-mediated fcc structure enhances strength while maintaining ductility, providing a novel mechanism for stabilizing the fcc phase at grain boundaries. It demonstrates a new strategy for producing Ti alloys with high strength and reasonable ductility by controlling the O level and strain.

The effects of Mn content on the Sn distributions, grain sizes, second phases, and mechanical properties of Cu-9Ni-6Sn-XMn alloys (wt.%, X = 0, 0.1, 0.5, and 1.0) were studied in this paper. The mechanisms of acting and strengthening through which Mn could promote grain refinement in the alloy were discussed. The results showed that the addition of Mn transforms the as-cast microstructure of the alloy into equiaxed grains, and the grains are obviously refined. When the amount of Mn is approximately 0.1 wt%, the average grain size of this alloy is 91.75 mu m, and the grain refinement effect is greatest in the experimental range. In addition, Mn increases the uniformity of the distribution of Sn in the as-cast microstructure. Differential scanning calorimetry (DSC) analysis revealed that the addition of Mn increases the undercooling of the as-cast Cu-9Ni-6Sn alloy and decreases in the critical nucleation radii of the grains. Further microstructure observation showed that Mn is dissolved mainly in the gamma-(Cu,Ni)3Sn phase. Consequently, the interfacial relationship between the gamma-(Cu,Ni)3Sn phase and the matrix transforms from incoherent to semicoherent. Compared with those of the Cu-9Ni-6Sn alloy, the strength and elongation of the alloy with added Mn are relatively great. When the content of Mn is 0.1 wt%, the strength of the alloy increases from 359.75 MPa to 423.54 MPa, while the elongation remains at 19.14 %. The synergistic effect of solution strengthening and fine grain strengthening of Mn is the main reason for the great improvement in the mechanical properties of the alloy.