scholarly journals Grain Refinement of Ti-15Mo-3Al-2.7Nb-0.2Si Alloy with the Rotation of TiB Whiskers by Powder Metallurgy and Canned Hot Extrusion

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 126 ◽  
Author(s):  
Jiabin Hou ◽  
Lin Gao ◽  
Guorong Cui ◽  
Wenzhen Chen ◽  
Wencong Zhang ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Tensile Test ◽  
Grain Refinement ◽  
Hot Extrusion ◽  
Dislocation Motion ◽  
Continuous Dynamic Recrystallization ◽  
Grain Sizes ◽  
The Matrix ◽  
Continuous Dynamic

In situ synthesized TiB whiskers (TiBw) reinforced Ti-15Mo-3Al-2.7Nb-0.2Si alloys were successfully manufactured by pre-sintering and canned hot extrusion via adding TiB2 powders. During pre-sintering, most TiB2 were reacted with Ti atoms to produce TiB. During extrusion, the continuous dynamic recrystallization (CDRX) of β grains was promoted with the rotation of TiBw, and CDRXed grains were strongly inhibited by TiBw with hindering dislocation motion. Eventually, the grain sizes of composites decreased obviously. Furthermore, the stress transmitted from the matrix to TiBw for strengthening in a tensile test, besides grain refinement. Meanwhile, the fractured TiBw and microcracks around them contributed to fracturing.

scholarly journals Controlled Grain Refinement of Biodegradable Zn-Mg Alloy: The Effect of Magnesium Alloying and Multi-Pass Hydrostatic Extrusion Preceded by Hot Extrusion

2020 ◽  
Vol 51 (12) ◽  
pp. 6784-6796
Author(s):  
Anna Jarzębska ◽  
Magdalena Bieda ◽  
Łukasz Maj ◽  
Robert Chulist ◽  
Daniel Wojtas ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Hot Extrusion ◽  
Fiber Texture ◽  
Hydrostatic Extrusion ◽  
Fine Grained ◽  
Continuous Dynamic Recrystallization ◽  
Consistent Model ◽  
Gradual Evolution ◽  
Textural Characterization ◽  
Continuous Dynamic

AbstractTo satisfy the most stringent criteria in terms of new cardiovascular stents, pure Zn was alloyed with 1 wt pct of Mg and subsequently subjected to plastic deformation, using conventional hot extrusion followed by multi-pass hydrostatic extrusion. A detailed microstructural and textural characterization of the obtained materials was conducted, and mechanical properties were assessed at each pass of deformation process. In contrast to pure Zn, hydrostatically extruded low-alloyed Zn is characterized by a remarkable increase in strength and ductility (YS = 383 MPa, E = 23 pct), exceeding the values needed for stents. Such behavior is associated with a dual microstructure containing fine-grained Zn, alternatively arranged with bands of a fragmented eutectic. Extensive grain refinement was achieved due to the process of continuous dynamic recrystallization. Hydrostatic extrusion changes the initial $$ \langle 10\bar{1}0\rangle $$ ⟨ 10 1 ¯ 0 ⟩ fiber texture to a 〈0002〉 and $$ \langle 10\bar{1}1\rangle $$ ⟨ 10 1 ¯ 1 ⟩ double fiber texture in which the 〈0002〉 component decreases with each pass of hydrostatic extrusion. The gradual evolution of texture components was simulated using a visco-plastic self-consistent model, which confirmed that, during hydrostatic extrusion, secondary slip systems were activated involving mostly the pyramidal one.

The contribution of friction stress to the creep behaviour of the nickel-base in situ composite, γ—γ'-Cr 3 C 2

1980 ◽  
Vol 373 (1752) ◽  
pp. 93-109 ◽  
Keyword(s):  
Activation Energy ◽  
Creep Behaviour ◽  
Friction Stress ◽  
Matrix Alloy ◽  
Dislocation Motion ◽  
Self Diffusion ◽  
The Matrix ◽  
Nickel Base ◽  
Distribution Of Stress

Transient creep following stress reductions has been analysed by the method described by McLean (1980) to determine the friction stress σ 0 as a function of temperature and directional solidification conditions for the γ-γ'-Cr 3 Cr 2 in-situ composite and for the γ-γ' matrix alloy. These values of σ 0 are identical to the flow stresses at creep strain rates and can be identified with the sums of the barriers to dislocation motion through the matrix by climb around γ'-particles and Orowan bowing between the carbide fibres. The friction stress and the kinetics of deformation of the composite are determined by the matrix behaviour, whereas its creep strength depends on the distribution of stress between fibre and matrix. When the steady-state creep behaviour of γ-γ'-Cr 3 C 2 is analysed by using the usual power law description in terms of the effective stress σ — σ 0 , rather than the applied stress σ, the stress exponent is ca 4 and the activation energy is similar to the activation energy of self-diffusion for nickel. The results provide strong evidence for the operation of recovery-creep in both the composite and matrix alloys.

scholarly journals Effect of Thermo-Mechanical Treatment on the Microstructure and Tensile Properties of the Fe-22Cr-5Al-0.1Y Alloy

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5696
Author(s):  
Hongyan Che ◽  
Yazhong Zhai ◽  
Yingjie Yan ◽  
Yongqing Chen ◽  
Wei Qin ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Mechanical Treatment ◽  
Oxide Dispersion Strengthened ◽  
Fusion Reactors ◽  
Oxide Dispersion ◽  
Grain Sizes ◽  
Powder Metallurgy Process ◽  
The Matrix ◽  
Thermo Mechanical Treatment ◽  
Metallurgy Process

Oxide dispersion strengthened ferritic steel is considered an important structural material in fusion reactors due to its excellent resistance to radiation and oxidation. Fine and dispersed oxides can be introduced into the matrix via the powder metallurgy process. In the present study, large grain sizes and prior particle boundaries (PPBs) formed in the FeCrAlY alloy prepared via powder metallurgy. Thermo-mechanical treatment was conducted on the FeCrAlY alloy. Results showed that microstructure was optimized: the average grain diameter decreased, the PPBs disappeared, and the distribution of oxides dispersed. Both ultimate tensile strength and elongation improved, especially the average elongation increased from 0.5% to 23%.

scholarly journals In-situ characterization of continuous dynamic recrystallization during hot torsion of an Al–Si–Mg alloy

2020 ◽  
Vol 822 ◽  
pp. 153282 ◽  
Author(s):  
David Canelo-Yubero ◽  
Zsolt Kovács ◽  
J.F. Thierry Simonet Fotso ◽  
Domonkos Tolnai ◽  
Norbert Schell ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Mg Alloy ◽  
In Situ Characterization ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Continuous Dynamic

scholarly journals Hot Deformation Behavior and Workability of In-Situ TiB2/7050Al Composites Fabricated by Powder Metallurgy

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5319
Author(s):  
Haofei Zhu ◽  
Jun Liu ◽  
Yi Wu ◽  
Qing Zhang ◽  
Qiwei Shi ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Grain Boundary Sliding ◽  
Hot Workability ◽  
Compression Tests ◽  
Hollomon Parameter ◽  
Continuous Dynamic Recrystallization ◽  
Fine Grain ◽  
Grain Structures ◽  
Tib2 Particles

Isothermal compression tests of in-situ TiB2/7050Al composites fabricated by powder metallurgy were performed at 300–460 °C with the strain rate varying from 0.001 s−1 to 1 s−1. The Arrhenius constitutive equation and hot processing map of composites were established, presenting excellent hot workability with low activation energies and broad processing windows. Dramatic discontinuous/continuous dynamic recrystallization (DDRX/CDRX) and grain boundary sliding (GBS) take place in composites during deformation, depending on the Zener-Hollomon parameter (Z) values. It is found that initially uniform TiB2 particles and fine grain structures are beneficial to the DDRX, which is the major softening mechanism in composites at high Z values. With the Z value decreasing, dynamic recovery and CDRX around particles are enhanced, preventing the occurrence of DDRX. In addition, fine grain structures in composites are stable at elevated temperature thanks to the pinning of dense nanoparticles, which triggers the occurrence of GBS and ensures good workability at low Z values.

Strengthening behavior of in situ -synthesized (TiC–TiB)/Ti composites by powder metallurgy and hot extrusion

2016 ◽  
Vol 95 ◽  
pp. 127-132 ◽  
Author(s):  
Shufeng Li ◽  
Katsuyoshi Kondoh ◽  
Hisashi Imai ◽  
Biao Chen ◽  
Lei Jia ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Hot Extrusion

Microstructural Evolution of AA6082 with Small Aluminides under Hot Torsion and Friction Stir Processing

2013 ◽  
Vol 753 ◽  
pp. 263-266 ◽  
Author(s):  
Cecilia Poletti ◽  
Friedrich Krumphals ◽  
Stefan Mitsche ◽  
Zeng Gao
Keyword(s):  
Local Deformation ◽  
Large Strains ◽  
Fem Simulations ◽  
Friction Stir ◽  
Fine Grained ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Continuous Dynamic ◽  
Hot Rolled

The hot rolled AA6082 aluminium alloy with aluminide dispersoids is deformed up to large strains to obtain a fine grained microstructure. Friction stir spot welding (FSSW) is carried out on rolled plates by means of a device provided by MTS System Corporation. FEM simulations determine that the material can flow up to local strains between 10 and 50 when the material reaches temperatures between 300-500°C. With this information, hot torsion tests at constant temperatures are carried out in a Gleeble ® 3800 machine for different strain rates. In both cases, in situ water quenching is applied to freeze the microstructure and avoid any static recrystallization effect after hot deformation. Light optical microscopy is used to identify the evolution of the grains as a function of the local deformation parameters determined by FEM simulations. The microstructure development by FSSW as well as by torsion is then further characterized by means of EBSD. At small strains the material deforms mainly by dynamic recovery with small low angle grain boundary formation and boundary dragging by fine aluminides and Mg2Si. At large strains grain refinement by continuous dynamic recrystallization takes place heterogeneously as a function of the original crystallographic orientation and precipitation state of each grain.

Phase Transformations in the Fe-Al System Studied by “In-Situ” Tem Heating

1994 ◽  
Vol 364 ◽  
Author(s):  
A. Korner
Keyword(s):  
Transition Temperature ◽  
Single Crystal ◽  
Domain Structure ◽  
Type A ◽  
Bimodal Distribution ◽  
Dislocation Motion ◽  
In Situ Tem ◽  
Transmission Electron ◽  
The Matrix

AbstractThe domain structure and the evolution of antiphase boundaries (APBs) have been investigated in Fe-Al by means of “in-situ” transmission electron microscopy (TEM) heating experiments. Single crystals with composition Fe22.1at%Al and Fe25.6at%Al have been used.The grown-in structure of the Fe22.1at%al single crystal is composed of DO3 ordered particles embedded in the disorderd ±-matrix. A bimodal distribution of the particles was found. Small ordered particles are in between the large precipitates which are surrounded by particle-free zones. Numerous of this large ordered precipitates contain APBs. Crossing the transition temperature to the disordered phase, the small particles dissolve into the ±-matrix and the large particles start to shrink by dissolving.The single crystal with composition Fe25.6at%Al was found to be completely DO3 ordered. The grown-in domains are separated by APBs of type a′0/2〈100〉. At temperatures far below the transition temperature to the B2 phase no significant change in the APB and domain structure has been detected. In contrast, a remarkable evolution in the APB structure has been observed approaching the transition temperature. Coarsening of the domains has been found. Furthermore, APBs of B2-type (a′0/4〈lll〉 shear) are dragged out by dislocation motion. B2- and DC3-type APBs react and junctions are formed. With increasing annealing time, the density of B2-type boundaries increases. The TEM image is dominated by B2-type boundaries linked by the D03-type boundaries. The DO3 superlattice spots are clearly excited approaching the transition temperature to B2. Above the transition temperature, the DO3 spots disappear completely and the diffraction pattern reveals B2 long range order.

Effect of Hot Extrusion on the Microstructure of In Situ TiB2 Particulate Reinforced Magnesium Matrix Composite

2011 ◽  
Vol 675-677 ◽  
pp. 473-476 ◽  
Author(s):  
N.N. Wu ◽  
C.F. Fang ◽  
Yun Bai ◽  
L.G. Meng ◽  
Hai Hao ◽  
...  
Keyword(s):  
Matrix Composite ◽  
Hot Extrusion ◽  
Magnesium Matrix Composite ◽  
Magnesium Matrix ◽  
The Matrix ◽  
Tib2 Particles ◽  
Deformation Modes ◽  
Particulate Reinforced ◽  
Main Deformation

The TiB2/AZ31 magnesium matrix composite was fabricated via self-propagating hightemperature synthesis (SHS) and then hot extruded. The influence of hot extrusion on the microstructure and property of TiB2/AZ31 composites was investigated. The results show that hot extrusion and synthesized TiB2 particles could refine the grain size obviously. The synthesized TiB2 particles are micro- and nano-sized, dispersing homogenously in the matrix. The interface between the matrix and the particles are good bonding. Meanwhile, slip and twinning are the main deformation modes during the hot extrusion. The fracture surface of hot-extruded TiB2/AZ31 magnesium matrix composite has more dimples than the as-cast AZ31 magnesium alloy. The improvement of microstructure seems to be beneficial for the fracture ductility of TiB2/AZ31 magnesium matrix composite.

The Role of Deformation Banding in Grain Refinement under ECAP

2014 ◽  
Vol 783-786 ◽  
pp. 2641-2646 ◽  
Author(s):  
Rustam Kaibyshev ◽  
Sergey Malopheyev ◽  
Vladislav Kulitskiy ◽  
Marat Gazizov
Keyword(s):  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Lamellar Structure ◽  
True Strain ◽  
High Angle ◽  
Continuous Dynamic Recrystallization ◽  
Angular Pressing ◽  
Deformation Banding ◽  
Continuous Dynamic

The mechanism of grain refinement in an Al-5.4Mg-0.4Mn-0.2Sc-0.09Zr alloy subjected to equal-channel angular pressing (ECAP) at 300°C through route BC is considered. It was shown that the formation of geometrically necessary boundaries (GNB) aligned with a {111} plane at ε≤1 initiates the occurrence of continuous dynamic recrystallization (CDRX). Upon further strain the GNBs transform to low-to-moderate angle planar boundaries that produces lamellar structure. In the strain interval 2-4, 3D arrays of planar boundaries evolve due to inducing the formation of 2nd order and higher orders families of GNBs in new {111} planes. GNBs gradually convert to high-angle boundaries (HAB) with strain. A uniform recrystallized structure is produced at a true strain of ∼8. The role of slip concentration and shearing patterns in the formation of GNBs is discussed.

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