scholarly journals Microstructure Evolution in Cu–0.5 wt% Zr Alloy Processed by a Novel Severe Plastic Deformation Technique of Rotational Constrained Bending

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 63
Author(s):  
Tomáš Krajňák ◽  
Miloš Janeček ◽  
Peter Minárik ◽  
Jenő Gubicza ◽  
Pham Tran Hung ◽  
...  
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Microstructure Evolution ◽  
Coarse Grained ◽  
Strong Increase ◽  
Heterogeneous Distribution ◽  
Size Refinement ◽  
Elongation To Failure ◽  
Constrained Bending ◽  
Zr Alloy

In the present study, a coarse-grained Cu–0.5 wt% Zr alloy was repeatedly processed by a novel technique of rotational constrained bending (RCB). In this technique, the workpiece was deformed by bending in a channel with an angle of 90°, using a rotating roller. The influence of the number of passes (N) of RCB on strain distribution, microstructure evolution and mechanical properties of the alloy was investigated. The heterogeneous distribution of the microhardness in the billet cross-section after the first pass was transformed into a homogeneous one after twelve passes, due to the rotation of the sample by 90° clockwise between individual passes. In addition, the gradual refinement/homogenization of the microstructure and formation of strong (110) crystallographic texture were found with increasing N. The initial grain size of 180 μm decreased down to 3.4 μm after twelve passes. The dislocation density increased by two orders of magnitude after RCB processing. In accordance with the grain-size refinement and the strong increase of the dislocation density, RCB processing significantly enhanced the strength of the alloy, while the ductility considerably decreased. The yield stress increased from 63 to 524 MPa, while the elongation to failure decreased below 10% after twelve passes.

Superplastic Behavior of a Cu-Cr-Zr Alloy Subjected to ECAP

2016 ◽  
Vol 838-839 ◽  
pp. 404-409
Author(s):  
Roman Mishnev ◽  
Iaroslava Shakhova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Strain Rate ◽  
Temperature Interval ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Superplastic Behavior ◽  
Average Grain Size ◽  
Gauge Section ◽  
Zr Alloy

A Cu-0.87%Cr-0.06%Zr alloy was subjected to equal channel angular pressing (ECAP) at a temperature of 400 °C up to a total strain of ~ 12. This processing produced ultra-fine grained (UFG) structure with an average grain size of 0.6 μm and an average dislocation density of ~4×1014 m-2. Tensile tests were carried out in the temperature interval 450 – 650 °C at strain rates ranging from 2.8´10-4 to 0.55 s-1. The alloy exhibits superplastic behavior in the temperature interval 550 – 600 °C at strain rate over 5.5´10-3 s-1. The highest elongation-to-failure of ~300% was obtained at a temperature of 575 °C and a strain rate of 2.8´10-3 s-1 with the corresponding strain rate sensitivity of 0.32. It was shown the superplastic flow at the optimum conditions leads to limited grain growth in the gauge section. The grain size increases from 0.6 μm to 0.87 μm after testing, while dislocation density decreases insignificantly to ~1014 m-2.

Simulation of Recrystallization Behavior and Austenite Grain Size Evolution during Hot Deformation of Low Carbon Steel Using the Flow Stress

2011 ◽  
Vol 337 ◽  
pp. 178-183 ◽  
Author(s):  
Jian Wang ◽  
Hong Xiao ◽  
Hong Biao Xie ◽  
Xiu Mei Xu
Keyword(s):  
Grain Size ◽  
Flow Stress ◽  
Dislocation Density ◽  
Microstructure Evolution ◽  
Hot Deformation ◽  
Process Model ◽  
Model Parameters ◽  
Flow Curves ◽  
Austenite Grain Size ◽  
Average Grain Size

Microstructure evolution can cause changes in dislocation density during hot plastic formation of metals and greatly influence the shape of flow curves. Recrystallization kinetics and average grain size were simulated by the coupled flow stress model describing dislocation development and microstructure evolution. The model for microstructure evolution considered different kinds of recrystallization in the same process rooted from nucleation and grain growth. Flow stress was calculated from the average dislocation density determined by the dislocation density model, which took into account hardening and recovery during the hot deformation process. Model parameters were defined by inverse analysis of flow curves obtained from hot compression tests and were completed through solving a nonlinear least-squares problem with constraints using optimization methods. Finally, the results obtained by the proposed model were compared with experimental results.

scholarly journals Titanium Ti6Al4V alloy reinforced by the addition of nano yttria stabilized zirconia fabricated by selective additive manufacturing: microstructure and mechanical investigations

2020 ◽  
Vol 321 ◽  
pp. 03018
Author(s):  
Amine HATTAL ◽  
Madjid DJEMAI ◽  
Jean Jacques FOUCHET ◽  
Thierry CHAUVEAU ◽  
Brigitte BACROIX ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Mass Density ◽  
Martensite Phase ◽  
Compression Tests ◽  
Stabilized Zirconia ◽  
Powder Mixtures ◽  
Size Refinement ◽  
Heat Treated ◽  
Elongation To Failure

Additive manufactured Ti6Al4V reinforced with nano yttria-zirconia (nYSZ) parts were fabricated using selective laser melting technology (SLM). The as-received Ti6Al4V powder and two powder mixtures of Ti6Al4V mixed with several nYSZ contents (1wt% and 2.5wt%) were prepared and then SLM processed. Parts were further subjected to a stress relief heat treatment. Besides, hot isostatic pressure (HIP) was used in order to eliminate residual porosities. The pycnometer-based technique was used to measure the mass density. XRD and EBSD analysis were performed to investigate the influence of nYSZ additions on the microstructure and subsequent mechanical properties via microhardness and compression tests. It was found that addition of nYSZ increases the density of the reinforced parts and produces a fine α martensite phase. Besides, the grain size was refined compared to that of heat treated Ti6Al4V. As a consequence, a significant increase in both the hardness and the compressive strength for the reinforced Ti6Al4V were obtained while the elongation to failure was kept. These improved mechanical properties are discussed in relation to the effect of nYSZ addition, which includes latice distortions and strengthening from grain size refinement and/or α formation.

Cyclic Behavior of Reversion-Treated Structures after Different Cold Rolling Reductions in an AISI 301LN Stainless Steel

2018 ◽  
Vol 786 ◽  
pp. 52-56
Author(s):  
Antti Järvenpää ◽  
Matias Jaskari ◽  
Pentti L. Karjalainen
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Cold Rolling ◽  
Stress Amplitude ◽  
Cyclic Hardening ◽  
Coarse Grained ◽  
Cyclic Behavior ◽  
Size Refinement ◽  
Cold Rolling Reduction ◽  
Cold Rolled

Lower cold rolling reductions before reversion annealing for the grain size refinement are desired in industrial practice. This study demonstrates the effect of a low (32%) cold rolling reduction on cyclic behavior of a partially reversed (750 °C for 0.1s) structure in a 17Cr-7Ni-N type 301LN austenitic stainless steel and compares it with those of a 63% cold rolled and annealed and with a conventional coarse-grained structure. Stress amplitude and the amount of deformation-induced martensite formed under cyclic loading at the 0.6% total strain amplitude were recorded. The results showed that the partially reversed structure after the 32% cold rolling reduction exhibits the similar cyclic stress amplitude level and slight cyclic hardening as the 63% cold-rolled counterpart does. Even though the grain size refinement remains less effective at the lower reduction, the microstructure consists of higher fractions of strong retained cold-deformed austenite and martensite phases which increase the flow resistance. However, the coarse-grained structure exhibits a much lower initial stress amplitude and much more pronounced cyclic hardening. The susceptibility of austenite to transform deformation-induced martensite is practically similar among these three structures. However, the cyclic hardening is a caused by the formation of deformation-induced martensite, and the difference in the degree of cyclic hardening results from the big difference in the strength of the austenite between the partially reversed fine-grained and coarse-grained structures.

Microstructure and Tensile Properties of a Mg-Zn-Y-Zr Alloy Containing Quasicrystal Phase Processed by Equal Channel Angular Pressing

2007 ◽  
Vol 353-358 ◽  
pp. 595-598 ◽  
Author(s):  
Shi Wei Xu ◽  
Ming Yi Zheng ◽  
Xiao Guang Qiao ◽  
Wei Min Gan ◽  
Kun Wu ◽  
...  
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Equal Channel Angular Pressing ◽  
Ecap Processing ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Texture Modification ◽  
The Matrix ◽  
Elongation To Failure ◽  
Zr Alloy

Equal channel angular pressing (ECAP) was performed on extruded Mg-Zn-Y-Zr (Mg-5.0wt%Zn-0.9wt%Y-0.2wt%Zr) alloy at 300 oC. After 8 ECAP passes, average grain size of the alloy was reduced to about 1.4 μm, and the quasicrystalline phases were broken and dispersed in the matrix. In addition, nano- quasicrystallines were precipitated from the matrix during ECAP processing. After ECAP, the elongation to failure of the extruded material was significantly improved. Only after 2 ECAP passes, the elongation to failure was 29%, and after 8 ECAP passes, it reached 35%, which was three times larger than that of the as-extruded alloy. However, both yield strength and ultimate tensile strength were decreased with the increasing ECAP passes, which was considered to be resulted from the {0002} basal plane texture modification during ECAP.

Dual-phase nanocrystalline Ni–Co alloy with high strength and enhanced ductility

2010 ◽  
Vol 25 (2) ◽  
pp. 401-405 ◽  
Author(s):  
Liyuan Qin ◽  
Jianshe Lian ◽  
Zhonghao Jiang ◽  
Guoyong Wang ◽  
Qing Jiang
Keyword(s):  
Grain Size ◽  
Room Temperature ◽  
High Strength ◽  
High Rate ◽  
Coarse Grained ◽  
Dual Phase ◽  
Ductile Materials ◽  
Average Grain Size ◽  
Elongation To Failure ◽  
Critical Scale

A dual-phase (DP) Ni–66.7%Co alloy with an average grain size of 16 nm was fabricated by electrodeposition. It exhibited an ultimate tensile strength of 1800–2080 MPa, together with an elongation to failure of 10–15% at room temperature. The remarkable ductility of this DP alloy with critical scale grains was attributed to its sustained high rate of strain hardening. Its fracture surface showed an unexpected deeply dimpled structure similar to that of coarse-grained ductile materials, which also witnesses the improved ductility.

Deformation Behavior of Ultrafine Grained Iron

2006 ◽  
Vol 503-504 ◽  
pp. 317-322 ◽  
Author(s):  
Setsuo Takaki ◽  
Kenji Kawasaki ◽  
Y. Futamura ◽  
Toshihiro Tsuchiyama
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Yield Stress ◽  
Grain Refinement ◽  
Work Hardening ◽  
Coarse Grained ◽  
Deformation Condition ◽  
Initial Yield Stress ◽  
Ultrafine Grained ◽  
Dislocation Strengthening

Work hardening behavior and microstructure development during deformation by cold rolling were investigated in iron with different grain size. Grain refinement makes the introduction of dislocation easier. For instance, under the same deformation condition (5% reduction in thickness), dislocation density is the order of 1014m-2 in a coarse grained material (mean grain size; 20μm), while it reaches 7×1015m-2 in an ultrafine grained material (0.25μm). It is well known that the yield stress of metals is enlarged with an increase in dislocation density on the basis of the Bailey-Hirsch relationship. However, it should be noted that the ultrafine grained material never undergoes usual work hardening although the dislocation density is surely enhanced to around the order of 1016m-2: 0.2% proof stress is almost constant at 1.4 ~ 1.5GPa regardless of the amount of deformation. The dislocation density of 1016m-2 is thought to be the limit value which can be achieved by cold working of iron and the yield stress of iron with this dislocation density (ρ) is estimated at 1.1GPa from the Bailey-Hirsch relationship; σd [Pa] = 0.1×109 + 10 ρ1/2. On the other hand, yield stress of iron is enhanced by grain refinement on the basis of the Hall-Petch relationship; σgb [Pa] = 0.1×109 + 0.6×109 d-1/2 as to the grain size d [μm]. This equation indicates that the grain size of 0.35 μm gives the same yield stress as that estimated for the limit of dislocation strengthening (1.1GPa). As a result, it was concluded that work hardening can not take place in ultrafine grained iron with the grain size less than 0.35 μm because dislocation strengthening can not exceed the initial yield stress obtained by grain refinement strengthening.

The Dislocation Structure and Deformation Mechanism of Tib2/Nial Composites

1990 ◽  
Vol 213 ◽  
Author(s):  
L. Wang ◽  
R.J. Arsenault
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Screw Dislocation ◽  
Dislocation Structure ◽  
Deformation Mechanism ◽  
Volume Fraction ◽  
Dislocation Generation ◽  
Screw Dislocations ◽  
Size Refinement ◽  
Dislocation Annihilation

ABSTRACTDislocation structures in 0, 10, and 20 V% TiB2/NiAl composites have been thoroughly investigated with a 1 MeV HVEM after compression testing at 760–1000° C. Samples with 0 and 10 V% TiBl2/NiAl additions have almost identical dislocation structures which can be described as a<100> screw dislocations with extensive jogs and superjoqs. Prismatically punched dislocations were observed in all of the deformed composites and deformed samples of 20 V% TiB2/NiAl had extensive dislocation generation around the particles. Dislocation density, grain size, and the tendency for dislocation reactions or networks forming during deformation decrease as the volume fraction of TiB2 increases. Also, since a predominance of screw dislocation was observed, the rate controlling process is not likely to be dislocation annihilation or climb, but dislocation generation. The grain size refinement could play an important role in the strengthening of the composites.

Microstructure and Mechanical Properties of Mg-Zn-Ca-Zr Alloy for Biomedical Application

2013 ◽  
Vol 774-776 ◽  
pp. 791-794
Author(s):  
Dong Mei Jiang ◽  
Liang Guo ◽  
Zhan Yi Cao ◽  
Xu Sun ◽  
Feng Xiao Huang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Biomedical Application ◽  
The Other ◽  
Tensile Yield Strength ◽  
Secondary Phases ◽  
Size Refinement ◽  
Microstructure And Mechanical Properties ◽  
Zr Alloy ◽  
Zr Alloys

The microstructure and mechanical properties of the as-cast Mg-Zn-Ca-Zr alloys were investigated in this study. The results showed that the alloy was mainly composed of α-Mg solid solution and the secondary phases of Ca2Mg6Zn3. The grain size of alloys decreased from 82 μm to 38 μm with Zr content from 0.1% to 0.5%. The addition of Zr greatly improved the ultimate tensile strength (σb) and elongation (ε), while slightly improved the tensile yield strength (σ0.2). The σb, ε and σ0.2 of the Mg-4Zn-0.5Ca-0.5Zr were 196MPa, 85MPa and 16.1% compared with the other two alloys. The reason was that grain size refinement strengthening enhanced the mechanical properties.

Microstructure Evolution and Mechanical Properties of Titanium Nickelide during Pressing in Equal-Channel Angular Matrix with Quasi-Small Angle of Channels Intersection

2021 ◽  
Vol 410 ◽  
pp. 123-127
Author(s):  
Abdrakhman B. Naizabekov ◽  
Dmitry V. Kuis ◽  
Andrey V. Kasperovich
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Microstructure Evolution ◽  
Small Angle ◽  
Titanium Nickelide ◽  
Coarse Grained ◽  
Ultrafine Grained Structure ◽  
Ultrafine Grained ◽  
Average Grain Size

The article presents the results of the analysis of the microstructure and mechanical properties of titanium nickelide formed during pressing in an equal-channel angular matrix with a quasi-small angle of channels intersection. The conducted studies have shown that pressing in an equal-channel angular matrix with a quasi-small angle of channels intersection ensures the formation of a homogeneous sub-ultrafine-grained structure in the titanium nickelide alloy, while the average grain size, decreasing by 100-200 times, is 0.3-0.5 microns, and the tensile strength increases to 1350 MPa in 6 passes, which is almost 90% higher than in the coarse-grained quenched state.

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