Effect of Ni Content on Microstructure and Characterization of Cu-Ni-Sn Alloys (original) (raw)
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Journal of Alloys and Compounds, 2004
The present work concerns study of the precipitation sequence due to aging below the critical aging temperature of cold-worked powder samples of industrially important Cu-Ni-Sn alloys with compositions, wt.% Sn. The analysis adopts a recently developed JAVA based software Materials Analysis Using Diffraction (MAUD), based on Rietveld's whole X-ray pattern fitting methodology. The evoluted phases have been characterized microstructurally in terms of different defect parameters, namely, stacking, twin and compound fault probabilities, crystallite (domain) sizes, microstrains (root mean square, rms strains), dislocation densities, preferred orientation parameters, etc. The analysis also includes quantitative estimation of phase abundances of the precipitating phases. The decomposition due to aging with varying Sn composition and aging period has been critically studied and the percentage of volume fraction of the evoluted phases has been evaluated and compared. The results depict, for the three different alloy compositions, three distinct different types of precipitation sequence comprising ␣, ␥ and ␦ phases with continuously varying volume fractions with aging time. The size-strain-shape analysis adopting the Popa model reveals almost isotropic values of both the crystallite sizes and rms strains in all [h k l] directions for the evoluted phases. The values of all the above defect parameters have been evaluated and compared for elucidating a better structure-property relationship. .in (M. De).
EFFECT OF COOLING RATE ON STRESS-STRAIN BEHAVIOUR AND MICROSTRUCTURE OF A CU- ZN- SN ALLOY
The effect of cooling rate on stress-strain behaviour and microstructure of Cu-11.89% Zn-7.68% Sn alloy was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), compression test. In this study, analysis results of the samples cooled in two different types (rapidly cooled in iced-brine and slowly cooled in furnace by homogenization in 750 o C have been evaluated. As a result of SEM observations, dendrite structures are observed in rapidly cooled sample and also dendrites together with annealing twins are observed in slowly cooled sample. From the XRD analysis of samples, two different phases (α-Cu and α-CuSn) have occurred and the sample cooled slowly has been indicates to give more intense peaks. The stress-strain curves obtained from compression tests of samples have been changing. When the alloy was cooled rapidly after heat-treatment, the yield strength is observed to increase and the reason of increase is linked to the increase of defect density as a result of fast cooling.
Microstructure and Mechanical Behavior of Hot Pressed Cu-Sn Powder Alloys
Advances in Materials Science and Engineering, 2016
Cu-Sn based alloy powders with additives of elemental Pb or C were densified by hot pressing technique. The influence of densifying on the properties of the hot pressed materials was investigated. The properties, such as the hardness, compressive strength, and wear resistance of these materials, were determined. The hot pressed Cu-Sn specimens included intermetallic/phases, which were homogeneously distributed. The presence of graphite improved the wear resistance of Cu-Sn alloys three times. Similarly, the presence of lead improved the densification parameter of Cu-Sn alloys three times. There was no significant difference in the mechanical behavior associated with the addition of Pb to the Cu-Sn alloys, although Cu-Pb alloys showed considerably higher ultimate strength and higher elongation. The Cu-Sn-C alloys had lower strength compared with those of Cu-Sn alloys. Evidence of severe melting spots was noticed in the higher magnifications of the compression fracture surface of 85% Cu-10% Sn-5% C and 80% Cu-10% Sn-10% Pb alloys. This was explained by the release of load at the final event of the fracture limited area.
Tensile strength of thermomechanically processed Cu-9Ni-6Sn alloys
Metallurgical and Materials Transactions A, 1999
The tensile properties of Cu-9Ni-6Sn alloys with different swaging amounts of 64, 77, and 95 pct, either solutionized and aged (S/A) or directly aged (D/A), were examined as a function of aging time. It was found that the aging response of Cu-9Ni-6Sn alloys varied greatly depending on the prior solution heat treatment before aging and/or different swaging amounts. The swaged S/A Cu-9Ni-6Sn alloys showed a multistage increase in tensile strength with respect to aging time, probably due to the sequential occurrence of spinodal decomposition, formation of metastable ␥и precipitates, and recrystallization. The effect of different swaging amounts, ranging from 64 to 95 pct, was minimal on the aging response of S/A specimens. The prior cold working, however, appeared to favor the spinodal strengthening, comparing unswaged and swaged S/A Cu-9Ni-6Sn alloys. In 95 pct swaged D/A Cu-9Ni-6Sn alloys, the level of hardening was much less sensitive to aging time. A complex interaction between the reduction in dislocation density, the formation of equilibrium precipitates, and the reduction of Sn content in the Sn-rich segregates during an aging process is believed to be responsible for such a lean sensitivity. The increases in tensile strength of 64 and 77 pct swaged D/A Cu-9Ni-6Sn alloys were found to be much steeper than that in the 95 pct counterparts in the early and intermediate stages of aging, which is believed to be related to the relative contribution from work hardening and precipitation hardening to the strength level of D/A specimens.
A study of precipitation in a Cu15 wt%Ni8 wt%Sn alloy
Journal of Materials Science Letters, 1999
The precipitation sequence in Cu-Ni-Sn alloys has been studied in several works . The results of these works have shown that the phase separation occurs spinodally in the early stage of the aging process. The decomposed phases are Sn-rich (α 1 ) and Sn-lean (α 2 ) phases, which have been reported difficult to be analyzed by transmission electron microscope (TEM) . Furthermore, it has been reported that the spinodal decomposition in a Cu-15 wt %Ni-8 wt %Sn alloy occurred only at aging temperatures below 723 K [3]; however, this result was concluded from samples aged for times as long as 10 min. This aging time seems to be too long to study the spinodal decomposition at the early stages, which may take place even during the quenching of solution treated samples. The purpose of this work is to study the early stages of phase separation in a Cu-15 wt %Ni-8 wt %Sn alloy aged at 673, 773 and 873 K for different periods of time, using X-ray diffraction analysis, as well as a field ion microscope, FIM, which has been shown to be an effective tool to study the phase separation at an early stage in different alloy systems.
Microstructure and Fatigue Behavior of a Ni-Cu-Sn Alloy
Metals
In this paper, the static and fatigue properties of a Cu-Ni-Sn alloy are investigated. Tensile tests, hardness tests and microstructural analyses using optical and scanning electron microscopy (SEM) were performed and two sets of fatigue tests, with load ratio (R) R = − 1 and R = 0 , respectively, were carried out. The results showed the capability of the alloy to bear high static stress, thanks to its good strength properties. However, the fatigue tests showed a strong sensitivity of the alloy fatigue properties depending on the raw material batch. The comparison between microstructural analyses and fatigue test results showed a strong correlation; in particular, the specimens having a more inhomogeneous microstructure showed lower durability. In addition, the different microstructure also affected the fracture surface morphology as highlighted by SEM analyses.
Microstructure and properties of CuNi2Si1 alloy processed by continuous RCS method
Purpose: Precipitation strengthened copper constitutes a group of functional and structural materials used where combination of high electrical conductivity with high strength is required. A growing trend to use new copperbased functional materials is recently observed world-wide. Within this group of materials particular attention is drawn to those with ultrafine grain size of a copper matrix. Design/methodology/approach: This study was aimed to investigate mechanical properties and microstructure in strips of age hardenable CuNi2Si alloy processed by continuous repetitive corrugation and straightening (CRCS). Tests were performed with quenched (900°C/1hour/water) or annealed (650°C /1 hour) 0.8 mm thick strips using original die set construction (toothed rolls and plain rolls set) installed in tensile testing machine. The changes of mechanical properties (HV, ultimate tensile strength, 0.2 yield strength) as well as microstructure evolution versus number of deformation cycles were investigated. The microstructure was investigated by optical and electron microscopy (TEM and SEM equipped with EBSD). Findings: The obtained strengthening effects and observed microstructure changes have been discussed basing on the existing theories related to strengthening of ultra fine grained copper based materials. Practical implications: The CRCS process effectively reduced the grain size of CuNi2Si1 alloy strips especially for annealed material, demonstrating the CRCS as a promising new method for producing ultra fine grained metallic strips. Originality/value: The paper contributes to the mechanical properties of precipitation strengthened ultra fine grained copper -chromium alloy strips obtained by original RCS method and to the microstructure evolution.