scholarly journals Modelling of Creep in Alloys Strengthened by Rod-Shaped Particles: Al-Cu-Mg Age-Hardenable Alloys

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 930 ◽  
Author(s):  
Chiara Paoletti ◽  
Michael Regev ◽  
Stefano Spigarelli
Keyword(s):  
Grain Size ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Creep Model ◽  
Modified Model ◽  
Physically Based ◽  
Excellent Description ◽  
The Difference ◽  
Temperature Exposure

In recent years, a creep model that does not involve adjustable parameters has been successfully applied to coarse-grained aluminum. The main feature of this model is that it is fully predictable. On the other hand, in the case of age-hardenable alloys, any physically-based creep model should take into account the changes in the volume fraction, size and distribution of strengthening precipitates, and the effect of grain size. With this aim in view, in this paper, the original model previously applied to single phase-alloys has been modified to describe the effects of the grain size and of the consequences of the high-temperature exposure on the strengthening role of precipitates. To this end, phenomenological equations describing the coarsening phenomena and their dependence on the applied stress have been introduced. The modified model has given an excellent description of the experimental behavior of an AA2024-T3 alloy tested at 250 and 315 °C and has provided a sound explanation of the difference observed when comparing the minimum creep rate obtained using two different testing techniques.

scholarly journals The Role of Microstructure on the Tensile Plastic Behaviour of Ductile Iron GJS 400 Produced through Different Cooling Rates—Part II: Tensile Modelling

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1019 ◽  
Author(s):  
Angella ◽  
Donnini ◽  
Ripamonti ◽  
Górny ◽  
Zanardi
Keyword(s):  
Grain Size ◽  
Ductile Iron ◽  
Volume Fraction ◽  
Interlamellar Spacing ◽  
Flow Curves ◽  
Cooling Rates ◽  
Plastic Behaviour ◽  
Microstructure Parameters ◽  
Explicit Correlation

Tensile testing on ductile iron GJS 400 with different microstructures produced through four different cooling rates was performed in order to investigate the relevance of the microstructure’s parameters on its plastic behaviour. Tensile flow curve modelling was carried out with the Follansbee and Estrin-Kocks-Mecking approach that allowed for an explicit correlation between plastic behaviour and some microstructure parameters. In the model, the ferritic grain size and volume fraction of pearlite and ferrite gathered in the first part of this investigation were used as inputs, while other parameters, like nodule count and interlamellar spacing in pearlite, were neglected. The model matched very well with the experimental flow curves at high strains, while some mismatch was found only at small strains, which was ascribed to the decohesion between the graphite nodules and the ferritic matrix that occurred just after yielding. It can be concluded that the plastic behaviour of GJS 400 depends mainly on the ferritic grain size and pearlitic volume fraction, and other microstructure parameters can be neglected, primarily because of their high nodularity and few defects.

Interface Diffusion in Cu Processed by Means of Surface Mechanical Attrition Treatment

2009 ◽  
Vol 289-292 ◽  
pp. 557-563 ◽  
Author(s):  
Z.B. Wang ◽  
K. Wang ◽  
K. Lu ◽  
Gerhard Wilde ◽  
Sergiy V. Divinski
Keyword(s):  
Grain Size ◽  
Surface Layer ◽  
Subsurface Layer ◽  
Coarse Grained ◽  
Surface Mechanical Attrition Treatment ◽  
Nanostructured Surface ◽  
Radiotracer Technique ◽  
Mechanical Attrition ◽  
The Difference ◽  
Effective Diffusivities

A nanostructured surface layer with a gradient microstructure was produced on a Cu plate by means of the surface mechanical attrition treatment (SMAT). Diffusion of Ni in the nanostructured layer was investigated by the radiotracer technique at temperatures from 383 to 438 K. The measured diffusion profiles consist of two distinct sections with different slopes, the steep one corresponding to the top surface layer with the grain size of 10 to 25 nm and the shallow one corresponding to a subsurface layer with a grain size of 25 to 100 nm. The effective diffusivities derived from both sections are more than 2 orders of magnitudes higher than the grain boundary diffusivities in coarse-grained Cu. The significantly accelerated diffusion rates are expected to be associated with the “non-equilibrium” states of interfaces in the nanostructured surface layer induced by SMAT. The difference between the diffusivities in the top and sub- surface layer might result from the fact that most interfaces developed from twin boundaries in the former while produced by dislocation activities in the latter.

scholarly journals Wear Behaviour of Nanocrystalline Fe88Si12Alloy in Water Environment

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Licai Fu ◽  
Jun Yang ◽  
Qinling Bi ◽  
Weimin Liu
Keyword(s):  
Grain Size ◽  
Wear Resistance ◽  
Friction Coefficient ◽  
Grain Boundary ◽  
Volume Fraction ◽  
Water Environment ◽  
Coarse Grained ◽  
Wear Behaviour ◽  
Phase Structures

Wear behaviour of nanocrystalline Fe88Si12alloy has been investigated in water environment compared with the coarse grained counterpart. The friction coefficient of the Fe88Si12alloy changes slightly with the grain size. The wear resistance is enhanced as the grain size decreases first and then reduces when the grain size continues to decrease, although the hardness of the Fe88Si12alloy decreases monotonically with the grain size. It is contrary to the predications of Archard’s formula. The best wear resistance of Fe88Si12alloy with grain size of 40 nm in our present work is attributed to the proper grain boundary volume fraction and composite phase structures of disordered B2 and ordered D03.

Structure and Fatigue Properties of the Mg Alloy AM60 Processed by ECAP

2008 ◽  
Vol 584-586 ◽  
pp. 803-808 ◽  
Author(s):  
Rinat K. Islamgaliev ◽  
Olya B. Kulyasova ◽  
Bernhard Mingler ◽  
Michael Zehetbauer ◽  
Alexander Minkow
Keyword(s):  
Grain Size ◽  
Endurance Limit ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Fatigue Properties ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Mean Grain Size ◽  
Fatigue Endurance ◽  
Misorientation Angles

This paper reports on the microstructures and fatigue properties of ultrafine-grained (UFG) AM60 magnesium alloy processed by equal channel angular pressing (ECAP) at various temperatures. After ECAP processing, samples exhibited an increase in fatigue endurance limit, which correlates well with a decrease in grain size. In case of lowest ECAP temperature, the mean grain size is as small as 1 2m which leads to an increase in fatigue endurance limit by 70 % in comparison to coarse-grained alloy. The temperature of ECAP not only governs the grain size and misorientation angles of grain boundaries but also the volume fraction of precipitates, thus affecting the probability of twinning and grain growth after fatigue treatment.

Piezoelectric Composites Based on Hydroxyapatite / Barium Titanate

2008 ◽  
Vol 54 ◽  
pp. 1-6 ◽  
Author(s):  
Chris R. Bowen ◽  
K.V.S. Raman ◽  
Vitaly Yu. Topolov
Keyword(s):  
Volume Fraction ◽  
Active Material ◽  
Ferroelectric Ceramic ◽  
Ceramic Composites ◽  
Batio3 Ceramic ◽  
Physical Factors ◽  
Electromechanical Properties ◽  
Modified Model ◽  
Perovskite Type

This paper reports experimental and modelling results on the manufacture and properties of hydroxyapatite / BaTiO3 ceramic composites and studies their electromechanical properties with ferroelectric ceramic volume fractions, mFC ³ 0.7. In these composites the bio-active properties of hydroxyapatite are combined with the electromechanical properties of a perovskite-type ferroelectric BaTiO3 ceramic in an attempt to create a novel polarised bone-substitute material. Experimental results of the volume fraction dependences of the effective piezoelectric coefficients * 31 d (mFC), * 33 d (mFC) and dielectric permittivity e *s 33 (mFC) of stress free samples are analysed within the framework of a modified model of a porous piezo-active material that is described in terms of 1–3 (one-dimensional rods in a continuous matrix) and 2–2 connectivity (laminates). The role of several structural elements and physical factors in forming the electromechanical properties of the composites is discussed. It is shown that performance of these materials typical properties are 5 pC / N < | * 31 d |< 45 pC / N, 20 pC / N < * 33 d < 100 pC / N and 400 < e *s 33 / 0 e < 1300.

scholarly journals Grain Size Effect of the γ Phase Precipitation on Martensitic Transformation and Mechanical Properties of Ni–Mn–Sn–Fe Heusler Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2339
Author(s):  
Jinpei Guo ◽  
Minting Zhong ◽  
Wei Zhou ◽  
Yajiu Zhang ◽  
Zhigang Wu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Martensitic Transformation ◽  
Annealing Time ◽  
Volume Fraction ◽  
Heusler Alloys ◽  
Coarse Grained ◽  
Dual Phase ◽  
Average Grain Size ◽  
Stress Hysteresis

Isothermal annealing of a eutectic dual phase Ni–Mn–Sn–Fe alloy was carried out to encourage grain growth and investigate the effects of grain size of the γ phase on the martensitic transformation behaviour and mechanical properties of the alloy. It is found that with the increase of the annealing time, the grain size and volume fraction of the γ phase both increased with the annealing time predominantly by the inter-diffusion of Fe and Sn elements between the γ phase and the Heusler matrix. The isothermal anneals resulted in the decrease of the e/a ratio and suppression of the martensitic transformation of the matrix phase. The fine γ phase microstructure with an average grain size of 0.31 μm showed higher fracture strength and ductility values by 28% and 77% compared to the coarse-grained counterpart with an average grain size of 3.31 μm. The fine dual phase microstructure shows a quasi-linear superelasticity of 4.2% and very small stress hysteresis during cyclic loading, while the coarse dual phase counterpart presents degraded superelasticity of 2.6% and large stress hysteresis. These findings indicate that grain size refinement of the γ phase is an effective approach in improving the mechanical and transformation properties of dual phase Heusler alloys.

Effect of Isothermal Aging on Microstructure and Creep Properties of SAC305 Solder: A Micromechanics Approach

2013 ◽  
Author(s):  
Preeti Chauhan ◽  
Subhasis Mukherjee ◽  
Michael Osterman ◽  
Abhijit Dasgupta ◽  
Michael Pecht
Keyword(s):  
Isothermal Aging ◽  
Solder Joints ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Creep Model ◽  
Secondary Creep ◽  
Dispersion Strengthening ◽  
Sac305 Solder ◽  
Particle Spacing ◽  
Cu6sn5 Imcs

SnAgCu (SAC) solders undergo continuous micro structural coarsening during both storage and service. In this study, we use cross-sectioning and image processing techniques to periodically quantify the effect of isothermal aging quantitatively on phase coarsening and evolution, in SAC305 (Sn3.0Ag0.5Cu) solder. SAC305 alloy is aged for (24–1000) hours at 100°C (∼ 0.7–0.8Tmelt). The characteristic parameters monitored during isothermal aging include size, volume fraction, and inter-particle spacing of both nanoscale Ag3Sn intermetallic compounds (IMCs) and micronscale Cu6Sn5 IMCs, as well as the volume fraction of pure tin dendrites in SAC305 solder. Effects of above microstructural evolution on secondary creep constitutive response of SAC305 interconnects were modeled using a mechanistic multiscale creep model. The mechanistic phenomena modeled include: (1) dispersion strengthening by coarsened nanoscale Ag3Sn IMCs and reinforcement strengthening by micronscale Cu6Sn5 IMCs, respectively; and (2) load sharing between pure Sn dendrites and the surrounding eutectic Sn-Ag phase. The coarse-grained polycrystalline Sn micro structure in SAC305 solder was not captured in the above model because isothermal aging did not appear to cause any significant change in the initial grain morphology of SAC305 solder joints. The above model is shown to predict the drop in creep resistance due to the influence of isothermal aging on SAC305 solder joints.

scholarly journals Effect of Cooling Rate on The Microstructure And Cryogenic Impact Toughness of HAZ in 9% Ni Steel

2021 ◽  
Vol 59 (11) ◽  
pp. 781-795
Author(s):  
Hae Won Eom ◽  
Joo Yeon Won ◽  
Sang Yong Shin
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Lath Martensite ◽  
Coarse Grained ◽  
High Angle ◽  
Tempered Martensite ◽  
Effective Grain Size

The effects of cooling rate on the microstructure and cryogenic impact toughness of coarse-grained heat-affected zone (CGHAZ) and inter-critically reheated coarse-grained HAZ (IC CGHAZ) in 9% Ni steel were investigated. CGHAZ and IC CGHAZ specimens were prepared from 9% Ni steel by controlling the cooling rate of the simulated welding process. The microstructure of the CGHAZ specimens consisted of autotempered martensite and lath martensite. As the cooling rate increased, the volume fraction of the autotempered martensite and the effective grain size decreased. A large amount of fine carbides was distributed inside the auto-tempered martensite, the dislocation density was low, and high angle grain boundaries were not observed. The microstructure of the IC CGHAZ specimens consisted of tempered martensite and lath martensite. As the cooling rate increased, the volume fraction of the tempered martensite and effective grain size decreased. Finer carbides were distributed inside the tempered martensite than in the auto-tempered martensite, the dislocation density was low, and high angle grain boundaries were not observed. Cryogenic fracture revealed that ductile fracture occurred in the auto-tempered martensite and tempered martensite, and brittle fracture occurred in the lath martensite. The crack propagation path was zig-zag in the high angle grain boundaries of the lath martensite. The volume fraction of auto-tempered martensite and tempered martensite and the effective grain size in the HAZ specimens had a significant effect on cryogenic impact toughness. In the IC CGHAZ specimens, cryogenic impact toughness decreased and then became constant as the cooling rate increased, due to a decrease in the volume fraction of the tempered martensite and effective grain size.

The Role of Boron in the Mechanical Milling of Titanium-6 %Aluminium-4% Vanadium Powders

1999 ◽  
Vol 581 ◽  
Author(s):  
A.P. Brown ◽  
R. Brydson ◽  
C. Hammond ◽  
T.M.T. Godfrey ◽  
A. Wisbey
Keyword(s):  
Grain Size ◽  
Mechanical Milling ◽  
Volume Fraction ◽  
Microstructural Development ◽  
Second Phase ◽  
Local Concentration ◽  
Fine Grained ◽  
Particle Form ◽  
Particulate Reinforced

ABSTRACTThe reduction in grain size of a metal can lead to significant improvement in mechanical properties. Mechanical alloying (MA) with a second phase is a possible route to producing fine-grained, particulate reinforced material. This study describes the microstructural development of Ti-6%Al-4%V milled with increasing concentrations of boron. Mechanical milling of Ti-6%Al-4%V powder produces a nanocrystalline material. MA of Ti-6%Al-4%V with boron results in the alloying of the two to form either a boride or an amorphous phase when the local concentration of boron is ∼ 50 at.%. During milling, the boron tends to remain near to its original particle form and in these boron-rich regions TiB is formed. Beyond these regions small amounts of boron (a few at.%) mix with the titanium matrix and reduce further the grain size of the titanium. An increase in the global concentration of boron increases the volume fraction of boride produced.

High Strain Rate Superplasticity in an Al-Mg-Sc-Zr Alloy Produced by Equal Channel Angular Pressing and Subsequent Cold and Warm Rolling

2012 ◽  
Vol 710 ◽  
pp. 223-228 ◽  
Author(s):  
Elena Avtokratova ◽  
Oleg Sitdikov ◽  
Oksana Mukhametdinova ◽  
Michael Markushev
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Equal Channel Angular Pressing ◽  
Volume Fraction ◽  
Warm Rolling ◽  
Strain Rate Range ◽  
Ambient Temperatures ◽  
Angular Pressing ◽  
The Difference ◽  
Zr Alloy

Superplastic (SP) properties of an Al−5%Mg−0.2%Sc−0.08%Zr alloy subjected to equal channel angular pressing (ECAP) at T=325°C with an effective stain of ~ 8 and subsequent rolling at the same and ambient temperatures were studied. It has been shown that the formation of ultrafine grained (UFG) structure with the grain size of about 1 μm and the volume fraction 0.6-0.7 under ECAP resulted in exceptionally high SP ductilities in a wide temperature - strain rate range. Maximum elongations ~3300% appeared at 475°C and the strain rate () of 5.6×10-2s-1. Subsequent warm rolling with a total reduction of 86% led to increased to 0.8-0.85 volume fraction of ultrafine grains with no changes in grain size. Cold rolling with reduction of 80%, in contrast, provided a heavily deformed structure with high dislocation density. In spite of the difference in the alloy microstructures, the SP properties in both rolled conditions were close to similar. The both states exhibited SP behavior with maximum elongation of ~ 2800% at 520°C and = 1.4 ×10-2s-1.

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