scholarly journals Precipitation in Solution-Treated Al-4wt%Cu under Cyclic Strain

2011 ◽  
Vol 172-174 ◽  
pp. 715-720 ◽  
Author(s):  
Adam Farrow ◽  
Campbell Laird
Keyword(s):  
Aspect Ratio ◽  
Elevated Temperatures ◽  
Cyclic Strain ◽  
Dislocation Motion ◽  
Precipitate Size ◽  
Precipitation Behavior ◽  
Solution Treated ◽  
Small Precipitate ◽  
Cutting Frequency ◽  
Equilibrium Vacancy

Solution-treated Al-4wt%Cu was strain-cycled at ambient temperature and above and the precipitation behavior investigated by TEM. In the temperature range 100°C to 200°C precipitation of Θ´´ appears to have been suppressed and precipitation of Θ´ promoted via cyclic strain. Anomalously rapid growth of precipitates appears to have been facilitated by a vacancy super-saturation generated by dislocation motion, with a diminishing effect observed at higher temperatures due to the faster recovery of non-equilibrium vacancy concentrations. Θ´ precipitates generated under cyclic strain are considerably smaller and more finely dispersed than those typically produced via quench-aging due to their heterogeneous nucleation on dislocations, and possess a low aspect ratio and rounded edges of the broad faces due to the introduction of ledges into the growing precipitates by dislocation cutting. Frequency effects indicate that dislocation motion, rather than the extremely small precipitate size, is responsible for the observed reduction in aspect ratio. Accelerated formation of grain boundary precipitates appears partially responsible for rapid inter-granular fatigue failure following cycling at elevated temperatures, producing fatigue striations and ductile dimples coexistent on the fracture surface.

The coprecipitation of Cr3P and Cr in Cu

1988 ◽  
Vol 46 ◽  
pp. 764-765
Author(s):  
M.J. Witcomb ◽  
U. Dahmen ◽  
K.H. Westmacott
Keyword(s):  
Orientation Relationship ◽  
Interface Structure ◽  
Model System ◽  
Relative Orientation ◽  
Age Hardening ◽  
Precipitation Behavior ◽  
Solution Treated ◽  
Small Needle ◽  
Diffraction Patterns ◽  
Interface Structures

Cu-Cr age-hardening alloys are of interest as a model system for the investigation of fcc/bcc interface structures. Several past studies have investigated the morphology and interface structure of Cr precipitates in a Cu matrix (1-3) and good success has been achieved in understanding the crystallography and strain contrast of small needle-shaped precipitates. The present study investigates the effect of small amounts of phosphorous on the precipitation behavior of Cu-Cr alloys.The same Cu-0.3% Cr alloy as was used in earlier work was rolled to a thickness of 150 μm, solution treated in vacuum at 1050°C for 1h followed by quenching and annealing for various times at 820 and 863°C.Two laths and their corresponding diffraction patterns in an alloy aged 2h at 820°C are shown in correct relative orientation in Fig. 1. To within the limit of accuracy of the diffraction patterns the orientation relationship was that of Kurdjumov-Sachs (KS), i.e. parallel close-packed planes and directions.

Cascade damage effects on the swelling of irradiated materials

1975 ◽  
Vol 346 (1644) ◽  
pp. 81-102 ◽  
Keyword(s):  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Heavy Ion ◽  
Rate Theory ◽  
Void Swelling ◽  
Solution Treated ◽  
Continuous Generation ◽  
Volume Swelling ◽  
Physical Features ◽  
Cascade Damage

The homogeneous rate theory of void growth is extended to include the possibility of forming vacancy loops when the irradiation produces cascade damage. The analysis provides a basis for understanding and correlating the relative swelling generated during electron; heavy ion and fast neutron irradiation. In order to illustrate the physical features of the model it is applied in some detail to calculating the volume swelling in solution treated M316 stainless steel for which there is a considerable amount of experimental data. The results from these calculations serve to expose the sensitivity of void swelling to the scale on which interstitial loops are nucleated. They also highlight the particular difficulty arising from the continuous generation of transmutation gas in predicting swelling under neutron irradiation at elevated temperatures.

Further experiments and modeling for microscale compression molding of metals at elevated temperatures

2007 ◽  
Vol 22 (7) ◽  
pp. 1839-1848 ◽  
Author(s):  
J. Jiang ◽  
W.J. Meng ◽  
G.B. Sinclair ◽  
E. Lara-Curzio
Keyword(s):  
High Temperature ◽  
Aspect Ratio ◽  
Tensile Testing ◽  
Elevated Temperatures ◽  
Low Cost ◽  
Mold Insert ◽  
Compression Molding ◽  
Mechanics Model ◽  
Replication Technique ◽  
High Temperature Tensile

Replication of metallic high-aspect-ratio microscale structures (HARMS) by compression molding has been demonstrated recently. Molding replication of metallic HARMS can potentially lead to low-cost fabrication of a wide variety of metal-based microdevices. Understanding the mechanics of metal micromolding is critical for assessing the capabilities and limitations of this replication technique. This paper presents results of instrumented micromolding of Al. Measured molding response was rationalized with companion high-temperature tensile testing of Al using a simple mechanics model of the micromolding process. The present results suggest that resisting pressure on the mold insert during micromolding is governed primarily by the yield stress of the molded metal at the molding temperature and a frictional traction on the sides of the insert. The influence of strain rate is also considered.

scholarly journals The Effects of Thermal Ageing on Properties and Microstructure of Al-6063 Alloy

2016 ◽  
Vol 694 ◽  
pp. 111-115
Author(s):  
C.N. Aiza Jaafar ◽  
I. Zainol ◽  
Mohd Amirul Zalif Mohamad Sapri
Keyword(s):  
Electron Microscope ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Thermal Ageing ◽  
Aged Alloy ◽  
Surface Fracture ◽  
Solution Treated ◽  
Transmission Electron ◽  
Peak Aged Condition ◽  
Peak Aged

The effect of thermal ageing on the properties and microstructure of Al-Mg-Si alloy was investigated. In this work, an extruded Al-6063 alloy samples were used as the main materials. In order to study the effect of thermal ageing, the alloy samples were solution treated at 530 °C and then quenched into water before artificially aged at elevated temperatures between 120 and 250 °C. The ageing response and mechanical properties was monitored by Vickers hardness and tensile tests, respectively. The analysis of surface fracture and microstructure of peak aged alloy were carried out by means of scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Result shows that the highest hardness value and tensile properties is gained by the alloy that aged at 120 °C. It is found that increasing in hardness and strength values of the alloy are due to precipitates formation during thermal ageing. Fracture analysis on peak-aged condition indicates that the alloy having more ductility after thermal ageing. The result shows that the higher ageing temperature will lead to the higher ductility of the Al-6063 alloy, as a results the alloy’s strength is reduced.

Mg-Zn-Y Alloys with Long-Period Stacking Ordered Phases: Deformation, Creep, Solute Segregation and Strengthening Mechanisms at Elevated Temperatures

2016 ◽  
Vol 879 ◽  
pp. 2204-2209 ◽  
Author(s):  
Zhi Qing Yang ◽  
Wei Wei Hu ◽  
Heng Qiang Ye
Keyword(s):  
Plastic Deformation ◽  
Creep Resistance ◽  
Basal Slip ◽  
Elevated Temperatures ◽  
Stacking Faults ◽  
Dislocation Motion ◽  
Tensile Creep ◽  
Lpso Phase ◽  
Long Period ◽  
Cottrell Atmospheres

Mg-Zn-Y alloys with long-period stacking ordered (LPSO) phases have superior strength at elevated temperatures. We studied plastic deformation and creep behavior of a Mg97Zn1Y2 (at.%) alloy. Deformation kinking of the LPSO phase plays an important role in strengthening the alloy during compression at elevated temperatures. Growth stacking faults with Zn/Y segregation can act as obstacles to non-basal slip and deformation twinning in Mg matrix. The tensile creep strain was only about 0.01% under a tensile stress of 70MPa for 100h at 200 °C, demonstrating excellent creep resistance of this alloy. Generation and motion of basal dislocations led to bending of LPSO phase during tensile creep of the Mg97Zn1Y2 (at.%) alloy. Plastic deformation in Mg grains was mostly achieved through basal slip during creep at temperatures below 200 °C, while non-basal slip through the generation and motion of “a + c” dislocations was activated with increasing the temperature to 200 °C and above. Dissociation of dislocations and Suzuki segregation on basal planes occurred widely in Mg matrix, which hindered dislocation motion and thus played an important role in preventing Mg grains from softening during deformation at elevated temperatures. In addition, Cottrell atmospheres were observed along dislocations in plastically deformed LPSO phase, impeding motion of dislocations. The superior strength and creep resistance of the Mg97Zn1Y2 (at.%) alloy at elevated temperatures are thus associated with the LPSO phase, stacking faults in Mg grains, formation of Cottrell atmospheres in LPSO and occurrence of Suzuki segregation in Mg.

In-Situ Tem Studies of Recrystallization and Grain Growth in Al-Mg-Mn-Zr Alloys

1995 ◽  
Vol 404 ◽  
Author(s):  
John S. Vetrano ◽  
Steve M. Bruemmer ◽  
Ian M. Robertson
Keyword(s):  
Grain Growth ◽  
Boundary Migration ◽  
Dislocation Motion ◽  
Precipitate Size ◽  
In Situ Tem ◽  
Eutectic Constituent ◽  
Cold Worked ◽  
Superplastic Properties ◽  
Zr Alloys

AbstractRecrystallization and grain growth studies of Al-Mg-Mn-Zr alloys have been carried out in-situ in the transmission electron microscope. Nucleation sites were primarily on large (>I μm diameter) eutectic constituent particles. The sub-micron A16Mn dispersoids were observed to be effective as nuclei if present in clusters, and were effective at retarding grain boundary migration and dislocation motion. The smaller A13Zr precipitates seemed to have little effect on nucleation and growth, but were effective in pinning dislocations. These results have been analyzed in terms of precipitate size and shape in both the as-cold-worked microstructure and during recrystallization. The implications on the microstructural refinement of these alloys for improved superplastic properties will be discussed.

scholarly journals In Situ Investigation with Neutrons on the Evolution of γ ' Precipitates at High Temperatures in a Single Crystal Ni-Base Superalloy

2011 ◽  
Vol 278 ◽  
pp. 42-47 ◽  
Author(s):  
Ralph Gilles ◽  
Debashis Mukherji ◽  
H. Eckerlebe ◽  
Pavel Strunz ◽  
Joachim Rösler
Keyword(s):  
Single Crystal ◽  
Size Distribution ◽  
Elevated Temperatures ◽  
Precipitate Size ◽  
Temperature Changes ◽  
Precipitate Size Distribution ◽  
Long Time ◽  
Sem Imaging ◽  
Base Superalloy

Single crystal Ni-base superalloys based on the  /  system are widely used in gas turbine applications. To understand the formation of  precipitates, including size distribution and growth, we performed in situ small-angle neutron scattering (SANS) measurements at elevated temperatures and - together with TEM as well as , SEM imaging - studied changes in the precipitates in short and long time scale. In the early stages, a bimodal precipitate size distribution of precipitate is observed, which (depending on the annealing temperature) changes to a cuboidal or nearly spherical morphology with almostmore or less uniform ( unimodal?) size distribution. [Note: The term "more or less" is several times repeated in the text. I cannot imagine what it in fact means. Could you change it or explain in a more clear way?]

Thermally Activated Dislocation Motion in an AS21 Alloy and Alloy Reinforced with Short Ceramic Fibres Studied at Elevated Temperatures

2013 ◽  
Vol 592-593 ◽  
pp. 71-74
Author(s):  
Zuzana Zdražilová ◽  
Zuzanka Trojanová ◽  
Kristián Máthis ◽  
Pavel Lukáč
Keyword(s):  
Magnesium Alloy ◽  
Stress Relaxation ◽  
Applied Stress ◽  
Elevated Temperatures ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Dislocation Motion ◽  
Thermally Activated ◽  
Effective Components ◽  
Thermally Activated Process

AS21 magnesium alloy (2.1Al-1Si-balance Mg in wt.%) and the alloy reinforced with short δ-Al2O3fibres (Saffil®) were deformed in compression at temperatures between 23 and 300 °C. Stress relaxation tests were performed in order to reveal features of the thermally activated dislocation motion. Internal and effective components of the applied stress have been estimated. The activation volume decreases with increasing effective stress. The values of the activation volume and the activation enthalpy indicate that the main thermally activated process in the alloy as well as in the composite is the dislocation motion in non-compact planes.

scholarly journals Influence of Solution Treatment Time on Precipitation Behavior and Mechanical Properties of Mg-2.0Nd-2.0Sm-0.4Zn-0.4Zr Alloy

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5037
Author(s):  
Tao Ma ◽  
Sicong Zhao ◽  
Liping Wang ◽  
Zhiwei Wang ◽  
Erjun Guo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Treatment Time ◽  
Solution Treatment ◽  
Basal Plate ◽  
Aged Alloy ◽  
Precipitation Behavior ◽  
Β Phase ◽  
Solution Treated ◽  
Strengthening Phases

The effect of solution treatment time on the microstructure and mechanical properties of aged the Mg-2.0Nd-2.0Sm-0.4Zn-0.4Zr (wt.%) alloy were investigated to give full play to the performance of the alloy. As the solution treatment time increased from 2 h to 12 h at 788 K, the grain size of the solution-treated alloy significantly increased, and the network-like β-Mg12(Nd, Sm, Zn) phase gradually dissolved into the α-Mg matrix. It should be noted that no obvious residual β phase can be observed when the solution treatment time was more than 8 h. After the solution-treated alloy was further aged at 473 K for 18 h, a large number of nanoscale precipitates were observed in the α-Mg matrix. The solution treatment time was 2 h, the α-Mg matrix mainly consisted of spherical-shaped and basal plate-shaped precipitates. Upon the increase of solution treatment time to 8 h, the key strengthening phases transformed from spherical-shaped precipitates and basal plate-shaped precipitates to prismatic plate-shaped β′ precipitates. The orientation relationship between β′ precipitates and α-Mg matrix was (1¯10)β′ // (11¯00)α and [112]β′ // the [224¯3]α. Further increasing of solution treatment time from 8 h to 12 h, the key strengthening phases mainly were still β′ precipitates. The solution treatment of aged alloy was carried out at 788 K for 8 h, which achieved optimal ultimate tensile strength (UTS) of 261 ± 4.1 MPa, yield strength (YS) of 154 ± 1.5 MPa, and elongation of 5.8 ± 0.1%, respectively.

Sign in / Sign up

Export Citation Format

Share Document