Effects of Grain Boundary on Age Hardening and Reversion in Al-Zn Alloys

1983 ◽  
Vol 77 (1) ◽  
pp. K49-K51 ◽  
Author(s):  
M. Ohta ◽  
A. Sakakibara ◽  
H. Yamada ◽  
M. Yamada ◽  
T. Kanadani
Keyword(s):  
Grain Boundary ◽  
Age Hardening ◽  
Zn Alloys

Effect of Surface and Grain Boundary on the Reversion of Al-Zn Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 1211-1216
Author(s):  
Keiyu Nakagawa ◽  
Teruto Kanadani
Keyword(s):  
Grain Boundary ◽  
Hardness Test ◽  
Age Hardening ◽  
Micro Hardness ◽  
Zn Alloy ◽  
Vickers Micro Hardness ◽  
Zn Alloys ◽  
Effective Source ◽  
Effect Of Surface

Age-hardening of Al-Zn alloy after quenching develops inhomogeneously due to the effect of surface as a vacancy sink and grain boundary as an easy path. In this study, reversion of the age-hardened Al-Zn alloys, in which ellipsoidal GP zones were formed, was investigated by Vickers micro-hardness test. Ellipsoidal GP zones were reverted more quickly near the surface and grain boundary than in the interior, as spherical GP zones in Al-10%alloy did. It is considered that the surface and grain boundary plays a role of effective source for vacancies, in addition to the interior source such as dislocations, as in the case of the reversion of spherical GP zones.

Hall-Petch Basis for Assessing Alloy Strengthening

1994 ◽  
Vol 362 ◽  
Author(s):  
Ronald W. Armstrong ◽  
R. Michael Douthwaite
Keyword(s):  
Grain Boundary ◽  
Alloy Composition ◽  
Friction Stress ◽  
Face Centered Cubic ◽  
Square Root ◽  
Petch Relation ◽  
Face Centered ◽  
Al Mg Alloys ◽  
Zn Alloys ◽  
Grain Boundary Strengthening

AbstractThe Hall-Petch relation σ = σo + kl−½, provides for the separate consideration of friction stress strengthening within the polycrystal grain volumes through σo and grain boundary strengthening through the product of the microstructural stress intensity k and the reciprocal square root of the grain diameter l Smaller grain diameters are normally obtained at higher alloy contents as illustrated for yield strength results reported for different face-centered-cubic Al-Mg alloys. Results on Al-Li alloy give an interesting example of substantial grain boundary strengthening that is associated with reduced ductility of the material. More complete results reported for the Cu-Al system, allow an evaluation of the strengthening component dependencies on alloy composition, in particular, connecting with a predicted square root of grain boundary obstacle stress in k. The much studied Cu-Zn alloys bring out subtle changes in σo and k

Grain boundary films in Al–Zn alloys after high pressure torsion

2014 ◽  
Vol 70 ◽  
pp. 59-62 ◽  
Author(s):  
B.B. Straumal ◽  
X. Sauvage ◽  
B. Baretzky ◽  
A.A. Mazilkin ◽  
R.Z. Valiev
Keyword(s):  
High Pressure ◽  
Grain Boundary ◽  
High Pressure Torsion ◽  
Boundary Films ◽  
Zn Alloys

Effect of Grain Size on Microstructure and Aging Behavior in AM60 Magnesium Alloy

2011 ◽  
Vol 409 ◽  
pp. 373-378
Author(s):  
H. Takano ◽  
Mitsuaki Furui ◽  
Susumu Ikeno ◽  
Tomoyasu Yamaguchi ◽  
Seiji Saikawa
Keyword(s):  
Grain Size ◽  
Magnesium Alloy ◽  
Grain Boundary ◽  
Eutectic Reaction ◽  
Age Hardening ◽  
Peak Hardness ◽  
Aging Behavior ◽  
Continuous Precipitation ◽  
Hardening Behavior ◽  
Average Grain Size

Our recent studies showed that continuous and cellular precipitates are covered with the whole of crystal grain in age hardable AM60 magnesium alloy cast into permanent molds, which have the average grain size of 75-85μm. Also, continuous precipitation is generated nearby grain boundary in the same alloys cast into sand molds, which have the average grain size of 138-147μm. It’s thought that permanent mold castings have the age hardening behavior of intragranular precipitation participation type that is influenced by continuous precipitates. It’s also thought that sand mold castings have the age hardening behavior of grain boundary participation type that is influenced by cellular precipitates. In this study, AM60 magnesium alloy with larger grain size was used to detect the grain size dependence of microstructure and aging behavior. In the microstructure of as-cast condition, the larger the grain size, it was shown that the none-equilibrium crystallized β phase with eutectic reaction during the solidification between liquidus and solidus temperatures becomes large-size. In the age hardening curves, the peak hardness values become higher with decreasing of grain size.

Grain Boundary Embrittlement and De-Embrittlement in Age Hardenable Iron Alloys

2012 ◽  
Vol 710 ◽  
pp. 11-18
Author(s):  
Yoon Uk Heo ◽  
Hu Chul Lee
Keyword(s):  
Grain Boundary ◽  
Critical Role ◽  
Aging Treatment ◽  
Iron Alloys ◽  
Age Hardening ◽  
Dislocation Glide ◽  
Ti Alloys ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement ◽  
Boundary Strength

Grain boundary embrittlement and de-embrittlement observed in age hardening iron alloys were reviewed. Fe-Mn-Ni and Fe-Ni-Ti alloys show excellent hardening response during aging treatment. However these alloys all suffer grain boundary embrittlemnt and show no tensile ductility even after very short aging treatment. Precipitation of intermetallic phases, θ-MnNi in Fe-Mn-Ni alloys and η-Ni3Ti in Fe-Ni-Ti alloys, at grain or lath boundaries was suggested as the reason for the weakening of grain boundary strength. Grain boundary strength recovered when these precipitates transform to austenite after extended aging. Dislocation glide or dislocation climb did critical role in conversion of these grain boundary precipitates to austenite.

Thermal evolution and grain boundary phase transformations in severely deformed nanograined Al–Zn alloys

2008 ◽  
Vol 56 (20) ◽  
pp. 6123-6131 ◽  
Author(s):  
B. Straumal ◽  
R. Valiev ◽  
O. Kogtenkova ◽  
P. Zieba ◽  
T. Czeppe ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Phase Transformations ◽  
Thermal Evolution ◽  
Boundary Phase ◽  
Zn Alloys

Ageing of C-Containing and C-Free Ti-15Cr and Ti-15-3

2007 ◽  
Vol 539-543 ◽  
pp. 3595-3600
Author(s):  
Xin Hua Wu ◽  
Joaquin Del Prado ◽  
D. Hu ◽  
A. Huang ◽  
M.Q. Chu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Age Hardening ◽  
Coarse Grain ◽  
Analytical Transmission Electron Microscopy ◽  
Hardness Testing ◽  
Optical Scanning ◽  
Transmission Electron ◽  
Boundary Alpha

Samples of Ti-15Cr and Ti-15V-3Sn-3Al-3Cr (wt%) containing controlled additions of carbon up to 0.2wt% and different oxygen contents have been quenched and aged at temperatures between 400 and 600°C. Optical, scanning and analytical transmission electron microscopy have been used to characterise the microstructures of the quenched and aged samples. Hardness testing has been used to follow the kinetics and extent of age hardening, which are accelerated in Ccontaining samples. The addition of carbon results in the formation of Ti(CxOy) precipitates which pin grain boundaries in forged samples so that the grain size in the quenched C-containing samples is about a factor of ten less than that in the C-free samples. In the C-free samples coarse grain boundary alpha tends to form, but in the C-containing samples alpha precipitation is more uniform throughout the beta grains. The extent of omega precipitation is very different in the two alloys; the Ti-15Cr alloy forms athermal omega in the as-quenched samples and large omega precipitates are formed on ageing at 400°C. No evidence for omega has been obtained in the Ti-15-3. The hardening responses and microstructural observations are interpreted in terms of the different grain boundary oxygen contents in the C-containing and C-free samples and the different roles of omega and of carbon in the two alloys.

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