Effect of Si and Ti on dynamic recrystallization of high-performance Cu-15Ni-8Sn alloy during hot deformation

Effect of Si and Ti on dynamic recrystallization(DRX)of Cu-15Ni-8 Sn alloy was studied using hot compression tests over deformation temperature range of 750-950℃and strain rate range of 0.001-10 s^-1.The results show that the dynamic recrystallization behavior during hot deformation is significantly affected by the trace elements of Si and Ti.The addition of Si and Ti promotes the formation of Ni16Si7Ti6 particles during hot deformation,which promotes the nucleation of dynamic recrystallization by accelerating the transition from low-angle boundaries(LABs)to high-angle boundaries(HABs).Ni16Si7Ti6 particles further inhibit the growth of recrystallized grains through the pinning effect.Based on the dynamic recrystallization behavior,a processing map of the alloy is built up to obtain the optimal processing parameters.Guided by the processing map,a hot-extruded Cu-15 Ni-8Sn alloy with a fine-grained microstructure is obtained,which shows excellent elongation of 30%and ultimate tensile strength of 910 MPa.

Wear map for sliding wear behavior of Cu-15Ni-8Sn alloy against bearing steel under oil-lubricated condition

Wear behaviors of a peak-aged Cu-15Ni-8Sn alloy fabricated by powder metallurgy were investigated.The results indicated that the friction coefficients and the wear rates of Cu-15Ni-8Sn alloy within a normal load range of 50−700 N and a sliding speed range of 0.05−2.58 m/s were less than 0.14 and 2.8×10−6 mm3/mm,respectively.Stribeck-like curve and wear map were developed to describe the oil-lubrication mechanism and wear behavior.The equation of the dividing line between zones of safe and unsafe wear life was determined.Lubricating oil was squeezed into micro-cracks under severe wear conditions.In addition,the lubricating oil reacted with Cu-15Ni-8Sn alloy to generate the corresponding sulfides,which hindered the repair of micro-cracks,promoted cracks growth,and led to delamination.This work has established guidelines for the application of the Cu-15Ni-8Sn alloy under oil-lubricated conditions through developing wear map.

Effect of applied load on transition behavior of wear mechanism in Cu-15Ni-8Sn alloy under oil lubrication

Tribological behavior of Cu-15Ni-8Sn(mass fraction, %) alloy against GCr15 ring under various loads was investigated on a ring-on-block tester in oil lubrication. The results showed that the wear rate increased slowly from 1.7×10^(-7) to 9.8× 10^(-7) mm^3/mm under the load lower than 300 N, and then increased dramatically to the climax of 216×10^(-7) mm^3/mm under the load over 300 N, which indicated the transition of wear mechanism with the increase of applied load. The wear mechanism mainly was plastic deformation and abrasive wear under the load less than 300 N. As the applied load was more than 300 N, the wear mechanism of Cu-15Ni-8Sn alloy primarily was delamination wear. Besides, the transition can also be confirmed from the different morphologies of worn surface, subsurface and wear debris. It is distinctly indicated that the appearance of flaky debris at the applied load over 300 N may be a critical point for the change of wear mechanism.

Microstructures of spinodal phases in Cu-15Ni-8Sn alloy

The microstructures of spinodal phases in Cu-15Ni-8Sn alloy were studied by TEM. It was found that when the alloy is completely in a as-quenched state, spinodal decomposition is quick. Ordering appears after spinodal decomposition. The ordered phase with DO22 structure has three variants obtained from coarsening spinodal structure. The reason of ordering appeared after spinodal decomposition is that the content of solute atoms needed by ordering is higher than the average, which can be reached by the composition fluctuation of spinodal decomposition. It was speculated that the morphology of the ordered phase is needle-like.

The Strengthening of Cu-15Ni-8Sn Alloy

The microstructure, property and relation between them of Cu-15Ni-8Sn alloy are studied by means of TEM and the measurement of hardness. The results show that y ’ metastable phase strengthens alloy because of its ordering structure. The ordering structure includes two types of and L12 ordering. Their strengthening for the alloy is much stronger than that of spinodal decomposition.

Ageing behavior of Cu-15Ni-8Sn alloy prepared by mechanical alloying

The ageing behavior of the mechanically alloyed Cu-15Ni-8Sn alloy has been studied. Compared with the alloys prepared by casting and rapid solidification, the modulation structure developed during ageing process of those prepared by mechanical alloying is finer and much more uniform, which leads to a higher peak hardness. However, their spinodal decomposition temperature are almost the same. Cold deformation prior to ageing not only accelerates the ageing process but also increases the peak hardness of the alloy.

Precipitation evolution and properties of Cu-15Ni-8Sn alloys via Al microalloying during ageing

Studies have shown that microalloying Cu-Ni-Sn alloys using Al inhibits discontinuous precipitation reactions;however,the mechanism has not been investigated yet.Thus,this study explored the properties and precipitation evolution of Cu-15Ni-8Sn alloys without and with 1 wt%Al(Cu-15Ni-8Sn-1Al)during ageing at 500℃ through X-ray diffraction(XRD),scanning electron microscopy and high-angle annular dark-field scanning transmission electron microscopy.The results revealed that in Cu-15Ni-8Sn alloy,DO_(22)ordering first occurred after spinodal decomposition,subsequently transitioning to an L1_(2)ordering phase,during which the discontinuous precipitates gradually nucleated at the grain boundaries and formed ingrains.The alloy hardness increased sharply with ordering and then decreased rapidly after reaching its peak value,due to the dominance of the discontinuous precipitation reaction.However,the DO_(22)ordered phase did not appear during the ageing of Cu-15Ni-8Sn-1Al alloy,and a Ni_(3)(Al_(x),Sn_(1-x))intermetallic compound with L1_(2)structure was formed,consuming Ni and Sn atoms,thereby significantly suppressing the discontinuous precipitation reaction and improving the stability during prolonged ageing.The tensile strength(yield strength)of Cu-15Ni-8Sn and Cu-15Ni-8Sn-1Al alloys at peak hardness were 855(755)and 936 MPa(892 MPa),respectively,and their main strengthening mechanisms were solid solution strengthening and precipitation strengthening.The addition of 1 wt%Al effectively improved the precipitation strengthening effect of Cu-Ni-Sn alloys but severely decreased the ductility.

放电等离子烧结Cu-15Ni-8Sn/石墨自润滑复合材料摩擦磨损性能研究

以Cu-15Ni-8Sn合金为基体,石墨为润滑剂,采用放电等离子烧结技术制备了Cu-15Ni-8Sn/石墨自润滑复合材料.使用扫描电子显微镜、X射线衍射仪和万能试验机研究了复合材料的微观组织、物相组成和室温力学性能,通过球-盘式摩擦试验机测试复合材料的摩擦磨损性能,利用三维轮廓仪测量材料磨损体积,借助扫描电子显微镜对磨痕形貌进行表征.结果表明:向Cu-15Ni-8Sn基体材料中添加石墨后,材料的硬度明显降低;随着石墨含量的提高,复合材料的抗压强度逐渐降低.当添加质量分数为3%的石墨时,Cu-15Ni-8Sn/石墨自润滑复合材料的耐磨性最好,磨损率最小为3.0×10^(-6)mm^(3)/(N·m),其磨损机理主要以磨粒磨损为主.

制备工艺对Cu-15Ni-8Sn合金晶粒特征和力学性能的影响

对比了Cu-15Ni-8Sn合金铸态、均匀化退火态(850℃×8 h)、锻造态、固溶态(840℃×1 h)和时效态(400℃×6 h)的硬度、强度和伸长率变化规律,分析了不同工艺状态下合金的显微组织和断口形貌。结果表明:铸态合金的组织为发达的树枝晶;经均匀化退火后,枝晶组织消失,层片状组织完全溶于铜基体;均匀化退火态合金经锻造后,晶粒尺寸明显减小,平均晶粒尺寸从58.78μm减小到4.22μm,抗拉强度由395.39 MPa提高到659.50 MPa,细晶强化为主要强化机制;固溶态合金由于溶质原子的充分固溶,伸长率大幅提升到46.7%;进一步经时效处理后,抗拉强度提高到802.50 MPa。

干摩擦条件下载荷和频率对Cu-15Ni-8Sn合金摩擦磨损性能影响研究

目的研究不同摩擦载荷及频率条件下Cu-15Ni-8Sn合金摩擦因数及磨损率的变化规律,探明机械参量变化对合金摩擦学性能的影响机制。方法采用熔炼法制备Cu-15Ni-8Sn合金,在干摩擦条件下对合金进行变载荷/变频率的销盘式往复摩擦实验,并对其摩擦因数、磨损率、磨损形貌及摩擦界面进行形貌及成分分析。结果随摩擦载荷的增大,2种载荷下Cu-15Ni-8Sn合金摩擦因数均呈现先增大后减小的趋势,整体在0.5~0.8之间;磨损体积随载荷的增加而增加;在2 Hz条件下合金的比磨损率随摩擦载荷的增大先降低后升高,在5 Hz条件下合金的比磨损率随摩擦载荷的增大先升高后降低;在高频高载条件下,磨损最为严重。磨痕及摩擦副表征结果显示,在干摩擦条件下,Cu-15Ni-8Sn合金主要以磨粒磨损和疲劳磨损为主;在摩擦过程中,合金基体及对偶同时发生磨损,剥落物以磨屑形式参与摩擦,因此在摩擦界面间发生元素转移。结论在干摩擦条件下,相较于摩擦频率,Cu-15Ni-8Sn合金受摩擦载荷的影响更大。合金磨屑以细小的颗粒状为主,但在低频率、高载荷条件下,会有大块片状磨屑。在干摩擦过程中,对磨副与合金之间会发生相互转移。随着载荷、频率的增加,摩擦层厚度也会变大,且摩擦过程中摩擦层内无剧烈氧化。

Effects of nanoscale Sn segregation on corrosion behavior of laser powder bed fusion Cu-15Ni-8Sn alloy

Corrosion resistance of laser powder bed fusion(LPBF)Cu-15Ni-8Sn alloys is crucial towards its practical application in marine engineering.In this work,corrosion behavior of LPBF Cu-15Ni-8Sn alloy was com-prehensively investigated.The results suggest that LPBF Cu-15Ni-8Sn alloy exhibits superior corrosion re-sistance than the conventional casting counterpart and their corrosion behavior is highly associated with Sn segregation.Generally,a triple-layer film will be formed on the surface of LPBF Cu-15Ni-8Sn alloy when being exposed to 3.5 wt%NaCl solution.To be more detailed,the abundance of nanoscale Sn-rich precipitates at the molten pool boundaries promotes the initial formation of a thick inner layer,where Ni and Sn tend to be distributed at inner and outer positions of the layer,respectively.In contrast,the inner layer on molten pools is much thinner ascribed to a lower Sn content,facilitating the earlier nucleation and growth of a compact middle layer that is mainly composed of numerous Cu-rich nanoparticles.At the outmost position,CuO,Cu(OH)_(2) and Ni(OH)_(2) constitute the major composition of the loose layer.The results of this study could contribute to the optimal design and processing of additively manufactured Cu-Ni-Sn alloys.

Effect of solidification rate on dendrite segregation and mechanical properties of Cu-15Ni-8Sn alloy prepared by directional solidification

The microstructures and mechanical properties of the directionally solidified Cu-15Ni-8Sn alloy were investigated at solidification rates ranging from 100 to 3000μm/s.The results showed that the solidification rate significantly affects the phase distribution of the as-cast Cu-15Ni-8Sn alloy.The primary and secondary dendritic spacing reduces and eventually becomes stable as the solidification rate increases.Meanwhile,the size of the primary phase decreases,and its distribution becomes more uniform.The most severe segregation problem of this alloy has been greatly improved.Upon solidification at 100μm/s,the as-cast Cu-15Ni-8Sn alloy consists of the α-Cu matrix,γ-CuNi_(2)Sn phase,discontinuous precipitation structure,modulated structure,and DO_(22) ordered phases.However,as the solidification rate increases,the discontinuous precipitation structure,modulated structures,and DO_(22) ordered phases decrease and even disappear,reducing hardness.As the solidification rate increases,after homogenization treatment,the composition and microhardness distributions of Cu-15Ni-8Sn alloy become more uniform.The time for homogenization is also shortened.It reduces production energy usage and facilitates further mechanical processing.

Age-hardening behavior and microstructure of Cu-15Ni-8Sn-0.3Nb alloy prepared by powder metallurgy and hot extrusion

Cu-15Ni-8Sn-0.3Nb alloy rods were prepared by means of powder metallurgy followed by hot extrusion.Element maps obtained by electron probe micro analyzer(EPMA)showed that Nb-rich phases were formed and distributed within grains and at grain boundaries of the Cu-15Ni-8Sn-0.3Nb alloy.Transmission electron microscope(TEM)results indicated that there was no obvious orientation relationship between these phases and the matrix.Spinodal decomposition and ordering transformation appeared at early stages of aging at400°C and caused significant strengthening.Cu-15Ni-8Sn-0.3Nb alloy exhibited both higher strength(ultimate tensile strength>1030MPa)and higher tensile ductility(elongation>9.1%)than Cu-15Ni-8Sn alloy after aging treatment.The improvement was caused by Nb-rich phases at grain boundaries which led o the refinement of grain size and postponed the growth of discontinuous precipitates during aging.

添加Si对Cu-15Ni-8Sn合金组织和性能的影响

利用金相显微分析、SEM、TEM及能谱分析对添加Si的Cu 15Ni 8Sn合金的组织结构和性能进行了研究。结果表明 ,添加的Si与Ni原子相结合 ,形成新相Ni3Si和Ni2 Si。在时效过程中 ,由于Ni2 Si相的析出 ,试验合金的电导率和硬度相对于Cu 15Ni 8Sn合金都有所提高。

Cu-15Ni-8Sn导电弹性材料的研究现状与进展

综述了Cu-15Ni-8Sn合金的研究概况,分析了合金性能的优势与不足。着重介绍了对合金性能的改进,并展望了合金的应用方向和发展趋势。

Evolutionary artificial neural network approach for predicting properties of Cu-15Ni-8Sn-0.4Si alloy

A novel data mining approach,based on artificial neural network(ANN) using differential evolution(DE) training algorithm,was proposed to model the non-linear relationship between parameters of aging processes and mechanical and electrical properties of Cu-15Ni-8Sn-0.4Si alloy.In order to improve predictive accuracy of ANN model,the leave-one-out-cross-validation (LOOCV) technique was adopted to automatically determine the optimal number of neurons of the hidden layer.The forecasting performance of the proposed global optimization algorithm was compared with that of local optimization algorithm.The present calculated results are consistent with the experimental values,which suggests that the proposed evolutionary artificial neural network algorithm is feasible and efficient.Moreover,the experimental results illustrate that the DE training algorithm combined with gradient-based training algorithm achieves better convergence performance and the lowest forecasting errors and is therefore considered to be a promising alternative method to forecast the hardness and electrical conductivity of Cu-15Ni-8Sn-0.4Si alloy.

铸造Cu-15Ni-8Sn合金的组织和力学性能

研究了铸造Cu-15Ni-8Sn合金时效过程中组织和力学性能的变化规律。固溶处理获得的单相α固溶体经适当的时效热处理会产生Spinodal调幅结构,亚稳态γ′相,以及不连续沉淀γ相。伴随着组织的变化合金的力学性能也相应发生变化,时效初期合金的强度和硬度随时效时间的延长或温度的升高而升高,而经过最大值后,则随时间的延长或温度的升高而下降;时效过程中合金塑性变化规律与强度和硬度规律相反。

铸造Cu-15Ni-8Sn-xTi合金的组织和硬度

研究了铸造Cu-15Ni-8Sn-xTi合金时效过程中组织和硬度的变化规律。研究表明,与Cu-15Ni-8Sn合金一样,含Ti的Cu-15Ni-8Sn合金能通过调幅结构及γ′强化相的形成而得到强化。0.073%的Ti能完全固溶于Cu-15Ni-8Sn合金中,并加速基体中γ′相和晶界胞状组织的形成和生长。当Ti含量超过0.300%时,Ni与Ti形成新相Ni3Ti,抑制γ′相的形成和生长,并完全抑制胞状组织的形成。

机械合金化和熔炼法制备的Cu-15 Ni-8Sn合金的Spinodal分解

利用透射电子显微镜 (TEM)和X射线多晶衍射仪 (XRD)观察分析了机械合金化 (MA)和熔炼两种方法制备的Cu 15Ni 8Sn(质量分数 ,% )合金在 40 0℃不同时效时间Spinodal分解产生的调幅组织结构和边带卫星峰 ,及合金固溶体的晶格参数变化。同时用维氏硬度计测量了合金的时效硬度变化。结果表明 ,与熔炼法相比 ,MA制备的该合金时效过程中 ,Spinodal分解初期的调幅组织结构波长较大 ,调幅分解速度也慢慢 ,延缓了γ′相的析出 ,但时效过程中二者硬度达到峰值的时间几乎是一致的。

Cu-15Ni-8Sn-0.4Si合金时效过程研究

用相对电导率、硬度的测量、金相分析及透射电镜等方法,研究了Cu 15Ni 8Sn 0.4Si合金在380℃时效过程中组织结构及性能的变化。结果表明,时效过程中,细小Ni2Si颗粒的析出对不连续沉淀有一定抑制作用;随时效时间增加,抑制作用减弱;Cu 15Ni 8Sn 0.4Si合金的电导率、硬度比Cu 15Ni 8Sn合金高。