Effect of Ti addition on tensile properties of Cu-Ni-Si alloys

This study examines how varying Ni and Si contents and the addition of Ti affect the tensile behavior of Cu-Ni-Si alloys with different aging conditions. Cu-3Ni-0.7Si and Cu-6Ni-1.4Si alloys, both with and without the addition of Ti, were prepared by solution-heat treatment at 950 °C for 2 h, then aged at 500 °C for 1/ 6 h, 1/3 h, 1/2 h, 1 h, 3 h and 6 h, before tensile tests were conducted. Doubling the Ni and Si contents in Cu-Ni-Si alloys greatly increased the tensile strength and grain refinement, while marginally reducing the tensile elongation. Meanwhile, adding Ti to Cu-Ni-Si alloys reduced the grain size and greatly increased the tensile elongation. The aging response was also significantly accelerated by the addition of Ti. However, the expected improvement in tensile strength was not obtained by adding Ti, addition due to the agglomeration of coarse Ni₂Si precipitates and the accelerated lamellar structure formation. Finally, we discuss the microstructural changes that result from variations in aging time, different Ni and Si contents and the addition of Ti on Cu-Ni-Si alloys based on detailed optical, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographic observations and SEM fractographic analysis.     

添加Ce与P+Sr复合变质对高硅耐热铝合金组织与性能的影响

研究了添加Ce与P+Sr复合变质对Al-21Si-1．5Cu-0．5Mg-2．5Fe合金显微组织与性能的影响。结果表明:添加1．5％Ce使粗大针状铁相消失,形成富Ce富Fe的鱼骨状相;P+Sr复合变质可使初晶硅平均尺寸由70 mm细化到20mm,共晶硅平均截线长降到2．1 mm,合金室温抗拉强度比未变质前提高21．5％,与P+Sr+Ce复合变质的Al-21Si-1．5 Cu-1．5Ni-2．5Fe-0．5Mg合金相当。     

Effect of Magnesium on Microstructure Refinements and Properties Enhancements in High-Strength CuNiSi Alloys

Microalloying is an effective method to improve the comprehensive properties of copper alloys.The effects of magnesium on the microstructure,mechanical properties and anti-stress relaxation properties of CuNiSi alloys have been investigated.Results demonstrated that magnesium plays significant roles in refining the dendritic microstructure of the as-cast ingot,accelerating the precipitation decomposition,improving the mechanical properties and increasing the anti-stress relaxation properties.The incremental strength increase is due to the Orowan strengthening from the nanoscale Ni_2 Si and Ni_3 Al precipitates.As compared with the Cu-6.0 Ni-1.0 Si-0.5 Al(wt%) alloy,the ultimate tensile strength of the designed Cu-6.0 Ni-1.0 Si-0.5 Al-0.15 Mg(wt%) alloy increases from 983.9 to 1095.7 MPa,and the electrical conductivity decreases from 27.1 to 26.6% IACS,respectively.The stress relaxation rates of the designed Cu-6.0 Ni-1.0 Si-0.5 Al-0.15 Mg alloy are 4.05%at 25℃,6.62% at 100℃and 9.74% at 200℃after having been loaded for 100 h,respectively.Magnesium significantly promotes nucleation during precipitation and maintains small precipitate size.     

冷加工Cu-Ni-Si和Cu-Ni-Si-Cr合金的分析(英文)

研究经冷加工和退火处理的过饱和Cu-2.65Ni-0.6Si和Cu-2.35Ni-0.6Si-0.6Cr合金。采用软件MAUD分析其显微组织参数的演变,包括晶粒尺寸、应变均方根和位错密度等。结果表明,经过冷加工和退火处理的两种合金的显微组织参数都具有特定值。在450℃时效2.5～3h的合金,其晶粒尺寸、应变均方根和位错密度等参数的净变化量与回复和再结晶过程相关。Cr作为第四组元添加到合金中没有明显改变形变和时效处理后合金的结构参数,因此也不影响合金的回复再结晶动力学。     

Influence of Si and Ti contents on the microstructure, microhardness and performance of TiAlSi intermetallics in Al-Si-Ti alloys

In this study, the influence of Si and Ti contents on the microstructure, microhardness and morphology of TiAlSi intermetallics in ternary Al-Si-Ti alloys was investigated. The increase of Si addition in Al-xSi-2Ti alloys leads to an increase of Si content in TiAlSi phase as well as an increase of microhardness. A phase evolution from Ti(Al_1−xSi_x)₃ to Ti₇Al₅Si₁₂ at about 14 wt.% Si was detected, while all the TiAlSi intermetallics exhibit flake-like. The increase of Ti content promotes the morphological transformation of TiAlSi from flake-like to block-like and primary Si particles are replaced by blocky TiAlSi particles in hypereutectic Al-Si alloy. The high-temperature strengthening effect of TiAlSi particles in a piston alloy was investigated and the strength is increased by 11.9% in this article, while the elongation and yield strength are increased by 17.6% and 10.1%, respectively.     

高强度Cu-Ni-(Al)-Si合金的组织和性能

通过光学显微镜、维氏硬度计、双臂电桥、扫描电子显微镜、透射电子显微镜等测试手段对Cu-5.2Ni-1.2Si和Cu-5.2Ni-1.5Al-1.2Si合金的组织结构和性能进行了表征与测试。结果表明:2种合金的铸态组织均为发达的树枝晶组织,包括白亮的枝晶区、非平衡凝固相粒子及中间过渡区。其中枝晶为富Cu区,凝固相为富Ni和Si区,Al元素则比较均匀地分布在铸态组织中。峰值时效后,Cu-5.2Ni-1.5Al-1.2Si合金具有比Cu-5.2Ni-1.2Si合金更高的硬度。Al元素不但促进了Ni2Si的沉淀析出,还形成了Ni3Al沉淀相,从而大大提高合金强度。2种合金的时效早期均出现了有序化,峰时效时主要为沉淀析出强化,合金具有较好的抗过时效能力。     

Microstructure and properties of high silicon aluminum alloy with 2% Fe prepared by rheo-casting

The morphology changes of both Fe-containing intermetallic compounds and the primary Si phase of Al-20Si-2Fe- 2Cu-0.4Mg-1.0Ni-0.5Mn (mass fraction, %) alloy produced by semi-solid rheo-diecasting were studied. The semi-solid slurry of high silicon aluminum alloy was prepared by direct ultrasonic vibration (DUV) which was imposed on the alloy near the liquidus temperature for about 2 min. Then, standard test samples of 6.4 mm in diameter were formed by semi-solid rheo-diecasting. The results show that the DUV treatment suppresses the formation of needle-like β-Al₅(Fe, Mn)Si phase, and the Fe-containing intermetallic compounds exist in the form of fine Al₄(Fe, Mn)Si₂ particles. Additionally, the primary Si grows up as fine and round particles with uniform distribution in a(Al) matrix of this alloy under DUV treatment. The tensile strengths of the samples at the room temperature and 573 K are 230 MPa and 145 MPa, respectively. The coefficient of thermal expansion (CTE) between 25 °C and 300 °C is 16.052 8×10^?6 °C^?1, and the wear rate is 1.55%. The hardness of this alloy with 2% Fe reaches HB146.3. It is discovered that modified morphology and uniform distribution of the Fe-containing intermetallic compounds and the primary Si phase are the main reasons for reducing the CTE and increasing the wear resistance of this alloy.     

Effect of V addition on hardness and electrical conductivity in Cu-Ni-Si alloys

The effect of vanadium (V) addition on the microstructure, the hardness and the electrical conductivity of Cu-2.8Ni-0.7Si alloys was investigated. The V-free, the 0.1 wt% V-added, the 0.2 wt% V-added Cu base alloys were exposed to the same experimental conditions. After the cold rolling of the studied alloys, the matrix was recrystallized during the solution heat treatment at 950 °C for 2 h. However, small amounts of vanadium substantially suppressed the recrystallization and retarded the grain growth of the Cu base alloys. The added vanadium accelerated the precipitation of Ni₂Si intermetallic compounds during aging and therefore it contributed positively to the resultant hardness and electrical conductivity. It was found that the hardness and the electrical conductivity increased simultaneously with increasing aging temperature and time with accelerated precipitation kinetics by the addition of vanadium. In the present study, the Cu-2.8Ni-0.7Si alloy with 0.1 wt%V was found to have an excellent combination of the hardness and the electrical conductivity when it was aged at 500 °C.     

Interfacial Bonding Strength Between Brazing Alloys and CVD Diamond

Three groups of brazing alloys were compared in brazing chemical-vapor-deposited (CVD) diamond, including two nickel-based alloys (Ni-3Fe-7Cr-3B-0.5Si-0.02C and Ni-14Cr-10P-0.02C), one copper-based alloy (Cu-10Sn-15Ti), and two silver-based alloys (Ag-5Cu-1Al-1.25Ti and Ag-34.25Cu-1In-1.75Ti). The nickel-based alloys catalytically transformed the sp³-bonded diamond into sp²-bonded carbon during high-temperature brazing operation though with the existence of Cr as the active metal. The bonding strength was very low and the fracture primarily propagated through the sp²-bonded carbon. For Cu-10Sn-15Ti brazing alloy, the transformation of the sp³-bonded diamond into sp²-bonded carbon during high-temperature brazing operation was marginal. The bond strength was adequate and fracture took place primarily through the brazing alloy bulk, due to the high concentrations of Sn and Ti that caused the precipitation of abundant intermetallic compounds in the brazing alloy bulk. For Ag-based alloys having very low concentrations of Ti, no visible degradation of diamond was observed and the bonding strength was very high. Crack primarily propagated through the brazed interface or even the CVD diamond bulk.     

Copper-titanium diboride coatings obtained by plasma spraying reactive micropellets

Electrotribological applications require materials with both high electrical conductivity and wear resisance. For this purpose, a copper- base plasma sprayed coating containing titanium diboride particles was developed. The process for fabricating this CU- TiB₂ coating consists of plasma spraying reactive powders that contain a Cu- Ti alloy and boron. The reaction between the copper alloy and boron proceeds in different steps going from solid- state diffusion of titanium and copper to the synthesis of TiB₂ in a liquid below 1083 ‡C. Plasma sprayed copper coatings contain finer TiB₂ crystals than Cu- TiB₂ materials synthesized in a furnace at 1200 ‡C. Coatings with 25 vol% TiB2 have hardnesses that are comparable to Cu- Co- Be and Cu- Ni- Be alloys and to Cu- W and Cu- Mo alloys used in spot welding. Their low electrical resistivity of 52 ΜΩ cm could be increased by lowering the oxygen content with coatings and controlling the formation of TiB₂ clusters, the titanium content in solution in copper remaining low after the synthesis reaction.     

Brazing of 6061 aluminum alloy/Ti-6Al-4V using Al-Si-Cu-Ge filler metals

Al-8.4Si-20Cu-10Ge and mixed rare-earth elements (Re) containing Al-8.4Si-20Cu-10Ge-0.1Re filler metals were used for brazing of 6061 aluminum alloy/Ti-6Al-4V. The addition of 20 wt.% copper and 10 wt.% germanium into the Al-12Si filler metal lowered the solidus temperature from 586 °C to 489 °C and the liquidus temperature from 592 °C to 513 °C. The addition of 0.1 wt.% rare-earth elements into Al-8.4Si-20Cu-10Ge alloy caused remarkable Al-rich phase refinement and transformed the needle-like Al₂Cu intermetallic compounds into block-like shapes. Shear strengths of the 6061 aluminum alloy/Ti-6Al-4V joints with the two brazing filler metals, Al-8.4Si-20Cu-10Ge and Al-8.4Si-20Cu-10Ge-0.1Re, varied insignificantly with brazing periods of 10-60 min. The average shear strength of the 6061 aluminum alloy/Ti-6Al-4V joints brazed with Al-8.4Si-20Cu-10Ge at 530 °C was about 20 MPa. Rare-earth elements appeared to improve the reaction of the Al-8.4Si-20Cu-10Ge filler metal with Ti-6Al-4V. The joint shear strength of the 6061 aluminum alloy/Ti-6Al-4V with Al-8.4Si-20Cu-10Ge-0.1Re reached about 51 MPa.     

A Novel Cu-10Zn-1.5Ni-0.34Si Alloy with Excellent Mechanical Property Through Precipitation Hardening

A novel Cu-10Zn-1.5Ni-0.34Si alloy was designed to replace the expensive tin-phosphor bronze in this paper. The alloy had better comprehensive mechanical properties than traditional C5191 alloy. The aged Cu-10Zn-1.5Ni-0.34Si alloy had a hardness of 220 HV, electrical conductivity of 28.5% IACS, tensile strength of 650 MPa, yield strength of 575 MPa and elongation of 13%. Ni₂Si precipitates formed during aging, and the crystal orientation relationship between matrix and precipitates was: (001)_α//(001)_δ, and [110]_α//[100]_δ. Ductile fracture surface with deep cavities was found in the alloy. Solid solution strengthening, deformation strengthening and precipitation strengthening were found to be core strengthening mechanisms in the alloy.     

Heat treatment effects on the corrosion resistance of some HVOF-sprayed metal alloy coatings

The present study evaluates the effects of a 600 °C, 1 h heat treatment on the corrosion resistance of three High Velocity Oxygen Fuel (HVOF) flame-sprayed alloy coatings: a Co-28Mo-17Cr-3Si (similar to Tribaloy-800) coating, a Ni-20Cr-10W-9Mo-4Cu-1C-1B-1Fe (Diamalloy-4006) coating and a Ni-32Mo-16Cr-3Si-2Co (similar to Tribaloy-700) coating. Electrochemical polarization tests and free corrosion tests were performed in 0.1 M HCl aqueous solution. The corrodkote test (ASTM B380-97R02) was also performed, to evaluate the coatings qualitatively. The heat treatment improves the corrosion resistance of the Co-28Mo-17Cr-3Si coating and of the Ni-20Cr-10W-9Mo-4Cu-1C-1B-1Fe coating by enhancing their passivation ability. The precipitation of sub-micron sized secondary phases after the treatment may produce galvanic microcells at intralamellar scale, but the beneficial contribution provided by the healing of the very small but dangerous interlamellar defects (normally present in thermal spray coatings but not detectable using ordinary scanning electron microscopy) prevails. The effect on Ni-32Mo-16Cr-3Si-2Co coatings is more ambiguous: its sensitivity to crevice corrosion is worsened by the heat treatment.     

Al-12Si-6Cu-1.5Ni-0.3Cr-0.2La-0.8Ce合金双级固溶处理工艺研究

以Al-12Si-6Cu-1.5Ni-0.3Cr-0.8Ce-0.2La铸造耐热铝合金为研究对象,对其进行双级固溶处理,以及人工时效。通过OM、SEM观察以及拉伸性能测试等手段,研究不同二级固溶温度和时间对合金显微组织和力学性能的影响。结果发现,随二级固溶温度升高和固溶时间延长,合金初生Si相钝化,共晶Si和网状相溶断成颗粒状或块状,室温和高温抗拉强度呈先增加后降低的趋势,当二级固溶温度达到530℃,时间为2h时综合性能最好。对试样进行200℃×6h的时效处理,并进行室温和高温(300℃)拉伸试验,结果表明,当合金经过490℃×2h+530℃×2h+200℃×6h热处理后,室温抗拉强度达342.0MPa,高温抗拉强度达到159.9MPa。     

Ti对SPS烧结Nb/Nb5Si3复合材料组织和性能的影响

以Nb、Si和Ti粉末为原料,采用放电等离子烧结(SPS)技术对Nb-20Si、Nb-20Si-5Ti、Nb-20Si-15Ti和Nb-20Si-24Ti材料进行原位合成。利用扫描电镜(SEM)、电子探针微区分析(EPMA)和X射线衍射(XRD)等手段对材料的组织结构进行分析,探讨Ti对复合材料组织和性能的影响规律。结果表明,Ti元素的加入使得复合材料中Nb5Si3相转变成(Nb,Ti)5Si3,随着Ti加入量的增加,组织中出现了单质的Ti相,当Ti含量达到24%时,组织中还会出现Nb3Si相;同时Ti的加入会降低复合材料的硬度,提高其高温抗氧化性能。     

Wetting Behavior of a Novel Al-Si-Ti Active Brazing Filler Metal Foil on Aluminum Matrix Composite

An active ternary brazing filler metal of Al-12Si-1Ti with a melting temperature range of 851-856 K was developed by adding Ti into Al-Si system alloy to improve the wettability of Al-Si system filler metal on pure aluminum matrix composite reinforced with short alumina fiber (Al₂O_3sf/Al). The wetting behavior of the developed Al-12Si-1Ti and conventional Al-12Si foils were compared using sessile drop test at 883 K for 300, 900, and 1800 s in flowing argon atmosphere. After shorter retardation periods, the interfacial gaps between Al-12Si-1Ti foil and matrix (M/M) micro-interfaces could disappear more easily than the case of using conventional Al-12Si foil. Moreover, the thickness of residual Al-12Si-1Ti foil also decreased faster than that of conventional Al-12Si foil. Especially, the interfacial gaps between reinforcement and filler metal (R/M) micro-interfaces could be eliminated for the developed Al-12Si-1Ti foil, while for conventional Al-12Si foil the interfacial gaps at R/M micro-interfaces could not be eliminated, although Si atoms could penetrate into the composite through bonded M/M micro-interfaces. These results showed that the Ti addition could not only accelerate the wetting at M/M micro-interfaces, but also eliminate the interfacial gaps at R/M micro-interfaces.     

Al-20Cu-4.5Si-3Ni-0.25RE合金的高温流变本构方程

在Gleeble-1500热模拟机上进行高温等温圆柱体压缩试验,研究Al-20Cu-4．5Si-3Ni-0.25RE合金在高温塑性变形过程中流变应力的变化规律。结果表明：应变速率和变形温度的变化强烈地影响Al-20Cu-4．5Si-3Ni-0．25RE合金的流变应力,流变应力随变形温度升高而降低,随应变速率提高而增大。可用Zener-Hollomon参数的双曲正弦形式来描述Al-20Cu-4．5Si-3Ni-0．25RE合金热压缩变形时的流变应力行为。     

Effect of solution treatment on microstructure and mechanical properties of as-cast Al-12Si-4Cu-2Ni-0.8Mg-0.2Gd alloy

Effect of solution treatment on microstructure and mechanical properties of Al-12Si-4Cu-2Ni-0.8Mg-0.2Gd alloy was investigated. Results show the Si particles become stable and more intermetallic compounds dissolve in the matrix after solution treatment at 500 °C for 2 h followed by 540 °C for 3 h (T4). The skeleton-like Al₃CuNi develops into two parts in the T4 alloy: one is Al₃CuNi which has the framework shape; the other is intermetallics including the Al₃CuNi (size: 5–10 µm) and AlSiCuNiGd phases (size: ≤5 µm) with complex structure. Adding 0.2% Gd can improve the mechanical properties of the alloys after two-step solution treatment (500 °C/2 h followed by 540 °C/3 h), the hardness of the alloy increases from 130.9 HV to 135.8 HV compared with the alloy with one-step solution treatment (500 °C/2 h), the engineering strength increases from 335.45 MPa to 352.03 MPa and the fracture engineering strain increases from 1.44% to 1.67%.

     

Microstructure and mechanical properties of laser melting deposited Ti2Ni3Si/NiTi Laves alloys

Two Ti2Ni3Si/NiTi Laves phase alloys with chemical compositions ofNi-39Ti-11Si and Ni-42Ti-8Si （%, mole fraction, the same below）, respectively, were fabricated by the laser melting deposition manufacturing process, aiming at studying the effect of Ti, Si contents on microstructure and mechanical properties of the alloys. The Ni-39Ti-llSi alloy consisting of Ti2Ni3Si primary dendrites and Ti2Ni3Si/NiTi eutectic matrix is a conventional hypereutectic Laves phase alloy while the Ni-42Ti-8Si alloy being made up of NiTi primary dendrites uniformly distributed in Ti2Ni3Si/NiTi eutectic is a new hypoeutectic alloy. Mechanical properties of the alloys were investigated by nano-indentation test. The results show that the decrease of Si and the increase of Ti contents change the microstructures of the alloys from hypereutectic to hypoeutectic, which influences the mechanical properties of the alloys remarkably. Corrosion behaviors of the alloys were also evaluated by potentiodynamic anodic polarization curves.     

喷射沉积Al-17Si-4Fe-2Mn-3Ni-3.5Cu-1Mg合金组织与性能

采用喷射沉积快速凝固技术制备了Al-17Si-4Fe-2Mn-3Ni-3.5Cu-1Mg合金,利用金相、XRD、SEM等测试方法分析了合金的组织特征、热稳定性及力学性能.结果表明,喷射沉积合金的组织由大量弥散分布的粒状相,少量块状相和共晶基体组成.合金在150、250、350 ℃下不同时间加热后,初晶Si没有明显的粗化.证明其在350 ℃下具有良好的热稳定性.合金经热处理后,室温抗拉强度达373 MPa.