Observations of Changes in Rate Dependent Flow of SnAgCu Solder Alloys Due to Aging

2009 ◽  
Author(s):  
Sri Chaitra Chavali ◽  
Kaushik Mysore ◽  
Ganesh Subbarayan ◽  
Indranath Dutta
Keyword(s):  
Diffusion Processes ◽  
Flow Behavior ◽  
Intermetallic Particle ◽  
Particle Growth ◽  
Secondary Creep ◽  
Aging Effects ◽  
Solder Alloys ◽  
Creep Tests ◽  
Snagcu Solder ◽  
And Behavior

Aging affects both microstructure and behavior [1, 2]. Microstructural changes are driven by dislocation motion and diffusion processes. Together they affect the flow behavior in solder alloys. We address four aspects of solder microstructure and behavior as affected by aging (a) EDS studies on Ag dispersion in Sn matrix (b) a procedure for modeling intermetallic particle growth (c) a model for estimating effective viscosity of solder alloy (d) both primary and secondary creep models to predict aging effects on behavior. Solder samples were aged for different aging times (15, 30, 60, 90 days aging) and at different aging temperatures (25 C, 75 C, 125 C) prior to running creep tests. Another set of solder samples were similarly aged to characterize the microstructure. The creep data for the experiments are from a series of sixty four experiments performed using a micromechanical tester that is specially fitted with a sensitive capacitance gauge (with a resolution of 0.1 microns) to accurately measure viscoplastic responses of solder to applied loads.

Mechanistic Model for Aging Influenced Steady State Flow Behavior of Sn3.8Ag0.7Cu Solder Alloys

2009 ◽  
Author(s):  
K. Mysore ◽  
S. Chavali ◽  
D. Chan ◽  
G. Subbarayan ◽  
I. Dutta ◽  
...  
Keyword(s):  
Steady State ◽  
Flow Behavior ◽  
Mechanistic Model ◽  
Secondary Creep ◽  
Aging Effects ◽  
Solder Alloys ◽  
Ambient Temperatures ◽  
Lap Shear ◽  
Random Microstructure ◽  
Mechanistic Basis

Sn3.8Ag0.7 Cu solder alloys age even at ambient temperatures. This significantly affects both microstructure and behavior of these alloys. In this work, aging influences on both are addressed. In particular, we discuss (a) honey comb type microstructure patterns in unaged samples and their subsequent evolution into a coarsened random microstructure at prolonged aging durations (b) aging effects on primary, secondary creep and on a range of applied loads and test temperatures through double lap shear experiments; the results show an increased tendency of aged solders to flow (c) a modified power law creep-plasticity model to predict aging effects on behavior. Possible mechanisms that result in the above behavior are also discussed; they motivate the mechanistic basis for the developed aging-informed behavior model, (d) procedures to compare alloys in terms of aging effects. Steady state creep strains, monotonic plastic strains and unified creep-plasticity theory are also discussed. Aging temperatures of −10 °C, 25°C, 75°C and 125°C, and aging times of 15, 30, 60 and 90 days (at each aging temperature) were selected as different levels of factors in a statistically designed experiment to study aging effects. Test specimens were selected with due pre-test considerations to joint-geometry, associated stress heterogeneity and joint-microstructures.

scholarly journals The Mixed-Electrode Concept for Understanding Growth and Aggregation Behavior of Metal Nanoparticles in Colloidal Solution

2018 ◽  
Vol 8 (8) ◽  
pp. 1343
Author(s):  
Johann Köhler ◽  
Andrea Knauer
Keyword(s):  
Metal Nanoparticles ◽  
Colloidal Solution ◽  
Particle Growth ◽  
Open Circuit ◽  
Aggregation Behavior ◽  
Nanoparticle Growth ◽  
Aspect Ratios ◽  
Spherical Metal Nanoparticles ◽  
High Yields ◽  
And Behavior

The growth and aggregation behavior of metal nanoparticles can be modulated by surfactants and different other additives. Here the concept of how open-circuit mixed electrodes helps to understand the electrical aspects of nanoparticle growth and the consequences for the particle geometries is discussed. A key issue is the self-polarization effect of non-spherical metal nanoparticles, which causes a local decoupling of anodic and partial processes and asymmetry in the local rates of metal deposition. These asymmetries can contribute to deciding to the growth of particles with high aspect ratios. The interpretation of electrochemical reasons for particle growth and behavior is supported by experimental results of nanoparticle syntheses supported by microfluidics which can supply high yields of non-spherical nanoparticles and colloidal product solutions of high homogeneity.

scholarly journals Creep Strain and Permeability Evolution in Cracked Granite Subjected to Triaxial Stress and Reactive Flow

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Fan Zhang ◽  
Jianjian Zhao ◽  
Dawei Hu ◽  
Qian Sheng ◽  
Jianfu Shao
Keyword(s):  
Acid Solution ◽  
Strain Rate ◽  
Creep Strain ◽  
Alkaline Solution ◽  
Confining Pressure ◽  
Creep Strain Rate ◽  
Reactive Flow ◽  
Secondary Creep ◽  
Creep Tests ◽  
Creep Stage

Fluid flow and fluid-rock interaction mainly take place in fracture network, consequently resulting in deformation and permeability variation of rock and deterioration of the wellbore performance. Mechanical-reactive flow coupling creep tests are performed on cracked granite under various confining pressures and acid and alkaline solution flows. The testing results show that the confining pressure and solution pH significantly influence the creep deformation, creep strain rate, and permeability. A primary creep stage and secondary creep stage are observed in all creep tests in this study; notably, the sample under a confining pressure of 10 MPa and acid solution injection undergoes creep failure for over 2700 hours. The acid solution has a more obvious influence on the creep behavior than that of the alkaline solution. With an increase in confining pressure, the total creep strain and creep strain rate in the samples gradually decrease during the injection of either solution. The permeability of the samples injected with either solution gradually deceases during the testing process, and this deceasing rate increases with the confining pressure. The scanning electron microscopy observations on the crack surfaces after the creep tests show that the surfaces of the fractures injected with the acid solution are smooth due to the dissolution of the matrix, while those injected with the alkaline solution include voids due to the dissolution of quartz. These experimental results could improve the understanding of the long-term transport and mechanical behaviors of wellbore.

scholarly journals Influence of Zirconia Plasma-Sprayed Coating on Creep of the Ti-6Al-4V Alloy

2006 ◽  
Vol 530-531 ◽  
pp. 690-695 ◽  
Author(s):  
Danieli A.P. Reis ◽  
Cosme Roberto Moreira Silva ◽  
Maria do Carmo de Andrade Nono ◽  
M.J.R. Barboza ◽  
Francisco Piorino Neto ◽  
...  
Keyword(s):  
Creep Resistance ◽  
Surface Oxidation ◽  
Constant Load ◽  
Nitrogen Atmosphere ◽  
High Temperature Strength ◽  
Secondary Creep ◽  
Creep Tests ◽  
Oxidation Protection ◽  
Sprayed Coating ◽  
Plasma Sprayed

The titanium affinity by oxygen is one of main factors that limit the application of their alloys as structural materials at high temperatures. Notables advances have been obeserved in the development of titanium alloys with the objective of improving the specific high temperature strength and creep-resistance properties. However, the surface oxidation limits the use of these alloys in temperatures up to 600°C. The objective of this work was estimate the influence of the plasma-sprayed coatings for oxidation protection on creep of the Ti-6Al-4V alloy, focusing on the determination of the experimental parameters related to the primary and secondary creep states. Constant load creep tests were conducted with Ti-6Al-4V alloy in air for coated and uncoated samples and in nitrogen atmosphere for uncoated samples at 500°C to evaluate the oxidation protection on creep of the Ti-6Al-4V alloy. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V specimens. Results indicated the creep resistance of the coated alloy was greater than uncoated in air, but nitrogen atmosphere was more efficient in oxidation protection. Previously reported results about the activation energies and the stress exponents values indicate that the primary and stationary creep, for both test conditions, was probably controlled by dislocation climb. Occurred a decreasing of steady state creep in function of the reduction of oxidation process, showing that Ti-6Al-4V alloy lifetime was strongly affected by the atmosphere due the oxidation suffered by the material.

Effect of Sb additions on the creep behaviour of low temperature lead-free Sn–8Zn–3Bi solder alloy

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Guang Ren ◽  
Maurice Collins
Keyword(s):  
Low Temperature ◽  
Solder Alloy ◽  
Creep Behaviour ◽  
Lead Free ◽  
Coefficient Of Determination ◽  
Secondary Creep ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Content Type ◽  
Free Solder

Purpose This paper aims to investigate the creep behaviour of the recently developed Sn–8Zn–3Bi–xSb (x = 0, 0.5, 1.0 and 1.5) low temperature lead-free solder alloys. Design/methodology/approach An in-house compressive test rig was developed to perform creep tests under stresses of 20–40 MPa and temperature range 25°C–75 °C. Dorn power law and Garofalo hyperbolic sine law were used to model the secondary creep rate. Findings High coefficient of determination R2 of 0.99 is achieved for both the models. It was found that the activation energy of Sn–8Zn–3Bi solder alloy can be significantly increased with addition of Sb, by 60% to 90 kJ/mol approximately, whereas the secondary creep exponent falls in the range 3–7. Improved creep resistance is attributed to solid solution strengthening introduced by micro-alloying. Creep mechanisms that govern the deformation of these newly developed lead-free solder alloys have also been proposed. Originality/value The findings are expected to fill the gap of knowledge on creep behaviour of these newly developed solder alloys, which are possible alternatives as lead-free interconnecting material in low temperature electronic assembly.

Comparison Between NACA 65 Profile and Circular Arc Blade Based on Numerical Investigation

2017 ◽  
Author(s):  
Tao Bian ◽  
Qianpeng Han ◽  
Martin Böhle
Keyword(s):  
Flow Structure ◽  
Lower Cost ◽  
Flow Behavior ◽  
Axial Flow ◽  
Leading Edge ◽  
Circular Arc ◽  
Spacing Ratio ◽  
Flow Loss ◽  
The Difference ◽  
And Behavior

For the axial flow fans NACA profiles have been well explored. However, the development and production of NACA profiles are also very expensive. Due to their lower cost of production circular arc blades are also applied to axial flow fans. But there is few information in the open literature focusing on flow loss and behavior of circular arc blades. Therefore, one question remains: how much is the difference of flow loss and behavior between NACA profiles and circular arc blades. In this paper NACA 65 profile and circular arc blade are examined by numerical method. The paper shows the flow loss of both blades in dependence of incidence, Reynolds number and spacing ratio. The occurrence of flow behavior, such as separation bubbles on the leading edge and flow structure on the sidewall is examined and discussed. The flow structure is given on basis of numerical flow picture. Additionally, the flow loss in the sidewall region of both investigated blades are worked out and compared.

The Formation and Behavior of Particles in Silane Discharges

1999 ◽  
Vol 557 ◽  
Author(s):  
Alan Gallagher
Keyword(s):  
Growth Rate ◽  
Film Growth ◽  
Particle Density ◽  
Plasma Chemistry ◽  
Particle Growth ◽  
Rf Plasma ◽  
Electrode Gap ◽  
Plasma Parameters ◽  
Rf Discharges ◽  
And Behavior

AbstractParticle growth in silane RF discharges, and the incorporation of particles into hydrogenated-amorphous-silicon (a-Si:H) devices is described. These particles have a structure similar to a-Si:H, but their incorporation into the device is believed to yield harmful voids and interfaces. Measurements of particle density and growth in a silane RF plasma, for particle diameters of 8-50 nm, are described. This particle growth rate is very rapid, and decreases in density during the growth indicate a major flux of these size particles to the substrate. Particle densities are a very strong function of pressure, film growth rate and electrode gap, increasing orders of magnitude for small increases in each parameter. A full plasma- chemistry model for particle growth from SiHm radicals and ions has been developed, and is outlined. It yields particle densities and growth rates, as a function of plasma parameters, which are in qualitative agreement with the data. It also indicates that, in addition to the diameter >2 nm particles that have been observed in films, a very large flux of SixH,, molecular radicals with × >1 also incorporate into the film. It appears that these large radicals yield more than 1% of the film for typical device-deposition conditions, so this may have a serious effect on device properties.

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