Precipitation hardening and recrystallization in Cu-4% to 7% Ni-3% Al alloys

The effects of microstructure on mechanical properties in three cold-worked Cu-4% to 7% Ni-3% Al alloys have been investigated by changing ageing time at 500 °C. Hardness and strength in the Cu-7% Ni-3% Al and Cu-5.5% Ni-3% Al alloys increase with ageing time and have maximum values at an ageing time of 10³–10⁴s at 500 °C, then decrease. During ageing of Cu-7% Ni-3% Al at 500 °C, the coherent Ni₃Al phase was first precipitated out and later incoherent NiAl phase was formed. Ni₃Al formed during the initial stage of ageing is likely to be a transient phase. The increases in hardness and strength are due to the precipitation of coherent Ni₃Al phase. Coherent Ni₃Al particles are effective in increasing the strength and retarding the recrystallization process. On the other hand, the hardness and strength in the Cu-4% Ni-3% Al alloy gradually declined with ageing time. Only incoherent NiAl phase was formed during ageing at 500 °C. Decreases in hardness and strength in the Cu-4% Ni-3% Al alloy are attributed to softening during recovery and recrystallization, because incoherent NiAl particles have an insufficient effect to increase the strength.     

Investigation on the Fe-based PM materials reinforced by In Situ synthesized TiC particulates

Atomized iron powder, carbonyl nickel powder, molybdenum powder, electrolytic copper powder, titanium powder and graphite powder were used as experimental materials; the titanium and graphite powders were added by an atomic ratio of Ti/C = 1:1 (the addition of Ti was 0 ～ 4 wt%) to Fe-2Ni-0.5Mo-2Cu-0.3C powder, and the iron-based powder metallurgy materials reinforced by in situ-synthesized TiC particulates were prepared by a powder metallurgy technique. The results show that the microstructures of sintered samples are mainly pearlite, ferrite and bainite. The amount of pearlite increases with the increase of Ti content, whereas the ferrite and bainite decrease. TiC particles sized 0.3 µm distribute mainly near the grain boundary of pearlite. The apparent hardness of sintered samples increases, while the sintered density and flexural strength decrease with the increase of Ti content. The fracture morphology of the sintered materials is brittle type.     

Plasma-assisted deposition of metal and metal oxide coatings

A combination of physical vapour deposition and plasma-assisted chemical vapour deposition techniques were used to deposit Cu-, Ni- and Sn-rich SnO/SnO2 coatings on metal and ceramic substrates. Cu and Ni were deposited on Al alloy 6061 substrates and Ni deposition was also performed on glass microscope slides and commercially pure alumina substrates. Sn-rich SnO/SnO2, on the other hand, was coated on stainless steel and pure Cu substrates. A direct-current plasma system was used to deposit the pure metals in vacuum with a resistively heated tungsten boat that was coated with alumina. All samples were sputtered for 20 min in an argon:hydrogen (1:1) atmosphere at a pressure of 300 mTorr. To reduce contamination and oxidation of both substrates and deposited layers, Cu and Ni coatings were made with argon:hydrogen (2:1) carrier gas. Sn-rich tin oxide coatings were deposited in a pure argon atmosphere (no hydrogen) to allow for the oxidation of Sn deposits on the stainless steel and copper substrates. Investigations of coated surfaces by scanning electron microscopy and X-ray diffraction showed coatings to be smooth, continuous and pure. Deposition rates showed this application to provide a very high rate when compared with chemical vapour deposition and metal–organic chemical vapour deposition techniques. Scratch tests results prove good attachment of the coatings to their respective substrates. © 1998 Chapman & Hall     

Mechanical properties of pure Ni and Ni-alloy substrate materials for Y-Ba-Cu-O coated superconductors

Mechanical properties of rolling-assisted, biaxially-textured substrates (RABiTS) and substrates for ion-beam assisted deposition (IBAD) coated superconductors are measured at room temperature, 76, and 4 K. Yield strength, Young’s modulus, and the proportional limit of elasticity are determined, tabulated and compared. Results obtained are intended to serve as a database of mechanical properties of substrates having the same anneal state and texture as those incorporated in the general class of RE-Ba-Cu-O coated conductor composites (RE = rare earth). The RABiTS materials measured are pure Ni, Ni-13at.%Cr, Ni-3at.%W-2at.%Fe, Ni-10at.%Cr-2at.%W, and Ni-5at.%W. The IBAD substrate materials included Inconel 625 and Hastelloy C-276. The Ni alloys are substantially stronger and show higher strains at the proportional limit than those of pure Ni. Substrates fully coated with buffer layers, ≈1 μm of Y-Ba-Cu-O, and 3-5 μm of Ag have similar mechanical properties (at 76 K) as the substrate alone. Somewhat surprisingly, plating an additional 30-40 μm of Cu stabilizer onto high-yield-strength (690 MPa) Hastelloy coated conductors ∼100 μm thick, reduces the overall yield strength of the composite structure by only about 10-12% at 76 K and 12-14% at room temperature; this indicates that the Cu layer, despite its relatively soft nature, contributes significantly to the overall strength of even high-strength coated conductors.     

Oxidation behaviour of titanium-containing brazing filler metals

Brazements on alumina or partially stabilized zirconia (PSZ) of four silver- or copper-based brazing filler metals that contain titanium to promote wetting of and adherence to structural ceramics, were exposed in a thermogravimetric analyser at temperatures up to 700°C to atmospheres of 100% O₂, Ar-20% O₂ and Ar-3 p.p.m. O₂. The alloys included Cu-41.1Ag-3.6Sn-7.2Ti, Ag-44.4Cu-8.4Sn-0.9Ti, Ag-41.6Cu-9.7Sn-5.0Ti and Ag-37.4Cu-10.8In-1,4Ti, at%. All formed external oxides that were more or less protective under all of the test conditions studied. The growth of the oxides followed a parabolic time law. The gains in weight due to oxidation observed were small, ranging (for 45 h exposure at 400 °C to Ar-20% O₂) from 0.20 mgcm⁻² for the Ag-37.4Cu-10.8In-1.4Ti alloy to 0.46 mgcm⁻² for Cu-41.1Ag-3.6Sn-7.2Ti. As expected, weight gain increased with increasing temperature or . Unexpectedly, the titanium played a minor role in the scale formed on any of the filler metals with a titanium oxide, TiO₂, being found on only one alloy — Ag-41.6Cu-9.7Sn-5.0Ti. The brazements on PSZ gained weight at a higher rate than comparative brazements on alumina. We attribute this behaviour to oxygen transport through the zirconia resulting in the growth of an interfacial layer of titanium oxide.     

The metallurgical behaviour during brazing of Ni-base alloy Inconel 600 to Si3N4 with Ag71Cu27Ti2 filler metal

Detailed observations were carried out on the metallurgical behaviour of joint-brazing of nickel based alloy Inconel 600 to Si₃N₄ with Ag71Cu27Ti2 filler metal, with emphasis on the interface between the filler metal and the Inconel 600 and the effects of nickel which was the predominant element in the base metal. Based on the experimental results, the mechanism of bonding Inconel 600 to the filler metal is attributed to the diffusion of silver and copper along the grain boundaries of the Inconel 600, which results in mechanical anchoring. The effects of nickel on the metallurgical behaviour of filler metal are summed up as enhancing the separation of silver- and copper-rich liquid phases from the molten filler metal; combining titanium and decreasing its activity in the reaction with Si₃N₄ at the interface with ceramics; promoting the diffusion of silver and copper into Inconel 600; and facilitating the flow of filler metal over the surface of Inconel 600.     

Dislocation structures in deformed Cu-Ni-Zn alloy single crystals

It is known that Cu-Ni-Zn alloy has an ordered structure Cu₂NiZn (Ll₂) by annealing between 573 and 623 K. In the present experiments, the effects of annealing on the dislocation structure were studied on Cu-Ni-Zn single crystals with several compositions. Thin foils cut parallel to the {111} planes were observed in a transmission electron microscope. The results obtained are as follows. (i) In Cu-5Ni-5Zn, Cu-10Ni-10Zn and Cu-15Ni-15Zn (at%), the stress-strain behaviour, slip mode and dislocation structure did not change by annealing at 573 K. However, the slip mode became more concentrated and localized, and dislocations emitted from a source tended to stay on the same slip plane, as the nickel and zinc concentrations increased. (ii) However, those properties in Cu-20Ni-20Zn and Cu-25Ni-25Zn changed drastically by annealing. As the ordering proceeded, uniform distributions of superlattice dislocations were observed. A typical dislocation configuration, with long screw and wavy-edged superlattice dislocations, took the place of piled-up unit dislocations. (iii) The facts that edge-type superlattice dislocations formed dipoles and their clusters, and that the secondary dislocation density was much lower than the primary one, implied that the elastic interaction of the primary edge-type superlattice dislocations on the nearby parallel slip planes would control the work-hardening of ordered Cu₂NiZn alloy single crystals.     

仿金铜合金的研制与应用

研制了一种新型艺术用Ｃｕ－６Ａｌ－２Ｎｉ－０．１Ｉｎ铜合金，其颜色为金黄色，有优良的耐蚀，异型铸造，压力加工和焊接性能，对其在海洋性气候下的防腐保护作了探讨。简单介绍了仿金铜合金在某大型雕塑上的应用。     

Influence of composition and processing parameters on mechanical properties and erosion response of Ni–TiB2 coatings

Abstract

Sputtered Ni–TiB₂ coatings have been shown to protect Ti–6Al–4V and Inconel 718 substrates from solid particle erosion. However, before new erosion resistant coatings can be efficiently designed, it is essential that the role of mechanical properties in determining erosion resistance be fully understood. In this investigation, nanoindentation techniques were used to quantify the effects of substrate preparation, coating composition, and sputtering process parameters on the elastic moduli and indentation hardness of thin coatings deposited on Ti–6Al–4V and Inconel 718 substrates. The influence of these parameters on coating adhesion was determined using a conventional scratch test. Elastic moduli, indentation hardnesses, and coating adhesion were correlated with erosion behaviour. The erosion resistance of the coatings that exhibited microscopic ductility is dependent on the nodule diameter and coating properties such as hardness, elastic modulus, and fracture toughness.

MST/1697     

Phase transformation behaviours and shape memory characteristics of Ti-45xNi-5Cu-xMo x=0.3-1.0 alloys

Abstract

Transformation behaviours and shape memory characteristics in Ti-45xNi-5Cu-xMo x=0.3, 0.5, or 1.0 at.- alloys were investigated by means of electrical resistivity measurements, differential scanning calorimetry, X-ray diffraction, thermal cycling tests under constant load, and tensile tests. The two stage transformation B2-B19-B19 occurred in Ti-45xNi-5Cu-xMo alloys, and complete separation of the B2-B19 transformation from the B19-B19 transformation was observed in Ti-44.0Mo-5Cu-1.0Mo at.- alloy. Substitution of Mo for Ni in Ti-45Ni-5Cu at.- alloy increased the critical stress for slip deformation and the pseudoelastic recovery. The maximum recoverable elongations of Ti-44.7Ni-5Cu-0.3Mo at.- and Ti-44.5Ni-5Cu-0.5Mo at.- alloys were 6.4 and 7 respectively.     

A study on dental nonprecious cast alloys

Tarnish tests conducted in a 0.1% sodium sulphide solution have shown that ternary nickel-copper-manganese alloys, such as 40Ni-30Cu-30Mn and 50Ni-30Cu-20Mn, have superior tarnishment resistance than other alloys, e.g. 20Ni-40Cu-40Mn, 30Ni-30Cu-40Mn and 30Ni-40Cu-30Mn. It was also found that 40Ni-30Cu-30Mn and 50Ni-30Cu-20Mn alloys have lower values of colour change vector than the other alloys given above.     

Flexible and lithography-compatible copper foil substrates for ferroelectric thin films

A process has been developed for preparing a low surface roughness copper foil by evaporation and subsequent peel-off of copper metal layers on glass slides. These 15 micron thick substrates exhibited roughness values between 1 and 2 nm root-mean-square (RMS) and 9 nm RMS over 25 μm² and 100 μm² analysis areas, respectively. The deposition and crystallization of barium strontium titanate layers were demonstrated on these smoother variant foils. The fully processed dielectric layers exhibited field tunability greater than 5:1, and could withstand fields in excess of 750 kV/cm. High field loss tangents below 0.007 were observed, making these materials excellent candidates for microwave devices. Finally, a process of lamination and contact lithography was used to demonstrate patterning of micron-scale features suitable for microwave circuit element designs.     

Growth of thick chemical solution derived pyrochlore La2Zr2O7 buffer layers for YBa2Cu3O7−x coated conductors

The preparation of several 100 nm thick La₂Zr₂O₇ (LZO) buffer layers on biaxially textured Ni-5 at.%W substrates using chemical solution deposition is studied. This oxide material is currently of great interest for the fabrication of YBa₂Cu₃O_7−x (YBCO) coated conductors. Buffer layers for these coated conductors are required to have thicknesses greater than 100 nm in order to guarantee a sufficient barrier function against metal diffusion from the substrate. In this work, single LZO buffer layers with thicknesses exceeding 200 nm have been prepared. Detailed investigations were carried out in order to study the texture development with increasing thickness as well as the microstructure of these layers. Independent of the thickness, high quality buffer layers showing a distinct biaxial texture up to the surface, smooth surfaces, and a sufficient barrier function against Ni diffusion from the substrate have been reproducibly obtained. The high performance of these chemical solution derived LZO buffer layers was confirmed by a YBCO critical current density J_c of 1.0 MA/cm² (77 K, 0 T) achieved for a coated conductor sample with a layer sequence YBCO/CeO₂/LZO(CSD)/Ni-5 at.%W where CeO₂ and YBCO were deposited by pulsed laser deposition.     

Preparation of Cu-TiN alloy by external nitridation in combination with mechanical alloying

A copper alloy dispersion strengthened by TiN was prepared by external nitridation in combination with mechanical alloying. After mechanical alloying pure Cu and Ti powders, a Cu-3wt.%Ti solid solution was formed. These powders were nitrided at 1073 K, resulting in a TiN layer on the surface of the copper powders. Further mechanical alloying was very efficient in breaking down the TiN surface layers. A very fine uniform distribution of nanosized TiN was obtained. The resulting copper alloy had a grain size of about 150 nm in diameter after annealing at 1173 K in vacuum for 5.4 ks, and showed a very high room temperature hardness value of 251 kg mm⁻² which was independent of annealing temperature below 1173 K.     

Comparative study of spinodal decomposition in symmetric and asymmetric Cu-Ni-Cr alloys

Spinodal decomposition in three alloys of nominal compositions 71Cu-27Ni-2Cr, 45Cu-45Ni-10Cr and 33Cu-52Ni-15Cr were studied by X-ray diffraction technique and transmission electron microscopy. It was found that the first and third alloys are asymmetric in nature while the second is symmetric. The symmetric alloy was found to decompose faster than the asymmetric ones. The asymmetry of the side bands was found to be related to the proportion of phases in the alloy. Electron microscopic studies revealed that during coarsening the major phase increases its connectivity by isolating the minor phase.     

Growth and characterization of shape memory alloy thin films for Si microactuator technologies

NiTi thin film alloys have been grown on Si (1 0 0) substrates by sequential multilayer deposition of Ni and Ti layers followed by metal interdiffusion via annealing. Short-time (5 min) annealing of the deposited layers at 500 °C leads to alloying of Ni and Ti, provided that preferential oxidation of Ti is avoided. This has been achieved by capping the layers with AlN, which constitutes a very efficient barrier preventing oxygen contamination of the film. For uncapped films, annealing has to be performed under high vacuum conditions. The structure of the processed films strongly depends on the temperature and time of the thermal process, obtaining Ni- and Ti-rich phases when the films are annealed at higher temperatures and/or during longer times. As-grown and processed films are analyzed by X-ray diffraction, in-depth Auger electron spectroscopy and X-ray photoelectron spectroscopy techniques. Finally, resistivity measurements show the existence of a phase transition in the films annealed at 600 °C without the capping layers (vacuum furnace). This contrasts with the behavior observed for AlN capped films, where cracking of the film occurs during cooling, which has been attributed to generation of stress in the buried film during the phase transition.     

Formation of thin nanostructured layers during heterogeneous gas-phase synthesis from small-size volatile metal complexes on the surface of semiconductors and dielectrics

We have developed and verified a new method for the formation of thin nanostructured layers on semiconductor and dielectric substrates by heterogeneous gas-phase synthesis from small-sized volatile metal complexes. Thin nanostructured layers of copper on silicon and silica substrates were successfully formed from small-sized volatile formiate metal complexes using a combined synthesis-transfer process. It is established that copper in the layers deposited by this method predominantly occurs in the metallic (Cu⁰) state in nanosized grains with a characteristic close-packed structure.     

Influence of Ti and Zr on the bond strength between carbon rod and Cu-Ti and/or Cu-Zr alloys

Influence of Ti and Zr in Cu matrix on the shear strength between Cu-Ti and Cu-Zr alloys and carbon rod was studied. Cu based specimens containing 0.7 and 3.6 wt.% Ti as well as 0.15; 1.3 and 5.1 wt.% Zr were prepared by hot pressing (HP) and hot isostatic pressing (HIP). In all cases, titanium diffuses to the boundary between carbon rod and Cu-Ti alloys and reacts with oxygen forming titanium oxides. Shear strength is higher for HIP specimens and increases with Ti content. The layer adjacent to carbon rod, in the case of Cu-Zr alloys, is pure copper (except for Cu-5.1 wt.% Zr alloy). The shear strength in this case is close to that of pure copper. For Cu-5.1 wt.% Zr the adjacent copper layer to C rod contains Cu-Zr particles. The shear strength is higher compared to Cu-0.15 and 1.3 wt.% Zr alloys, which can be due to the presence of this complex layer.     

Electromigration testing of Ti: W/Al and Ti: W/Al-Cu film conductors

Electromigration-induced failures in metal film interconnections influence the reliability of integrated circuits. For shallow (< 1 μm) junction devices a barrier- metal interconnection system such as Ti: W/Al has been proposed to eliminate contact pitting due to silicon-aluminum reactions. The addition of copper to aluminum films is known to improve the electromigration resistance of aluminum film interconnections. Glass-passivated Ti: W/Al and Ti: W/Al-Cu (1.6 wt.% Cu) film conductors (9 μm wide, 1.14 mm long and 170 nm/800 nm thick) on oxidized silicon substrates were subjected to a current stress of 10⁶ A cm^-2 in the temperature range 150–270°C. Mean-time-to-failure data indicate an improvement of approximately a factor of two in electromigration resistance due to the addition of copper. This improvement is smaller than that reported by others. Life test data are consistent with activation energies of 0.61±0.05 and 0.71±0.03 eV for Ti: W/Al and Ti: W/Al-Cu film conductors respectively. Extrapolated mean times to failure are close to 24 and 100 a for Ti: W/Al and Ti: W/Al-Cu films respectively under a current stress of 5 × 10⁵ A cm^-2 at 55°C ambience. Projected failure rates at these operating conditions increase very rapidly with time and approach values of 9 × 10^-7 and 1 × 10^-11 h^-1 for Ti: W/Al and Ti: W/Al-Cu film conductors respectively at 100 000 h.     

Ion-plated thick films of Al2O3 on stainless steels and Inconel

Gasless ion-plated films of Al₂O₃ and various alloys which served as adhesion layers were evaluated for thermal cycling stability and abrasion resistance. Substrates included Inconel and 304, 310 and 316 stainless steel test plaques. Work was extended to include the coating of the internal surface of Inconel cylinders. Both resistance-heated (tungsten baskets) and induction-heated (I-Gun^tm ion source) sources were used with combination r.f. and d.c. biasing.