Development of Thixoextrusion Process for 7000 Series Al Wrought Alloys

2006 ◽  
Vol 116-117 ◽  
pp. 771-774 ◽  
Author(s):  
Young Ok Yoon ◽  
Hyung Ho Jo ◽  
Jin Kyu Lee ◽  
Dong In Jang ◽  
Shae K. Kim
Keyword(s):  
Liquid Fraction ◽  
Isothermal Holding ◽  
Semisolid State ◽  
Grain Sizes ◽  
Partial Remelting ◽  
Different Content ◽  
Hardness Values ◽  
Holding Temperature

Thixoextrusion for 7003 and 7075 Al wrought alloys with different content of Cu was carried out with respect to isothermal holding temperature in the partially remelted semisolid state. Especially, despite higher extrudability index of 7075 Al wrought alloy compared with the extrudability index of 7003 Al wrought alloy, the maximum extrusion pressures of 7075 Al wrought alloy were about the same as the maximum extrusion pressures of 7003 Al wrought alloy at temperature with the liquid fraction 10% (7003-624, 7075-609). The hardness values of thixoextruded specimens were higher than that of as-quenched specimens only after partial remelting. The microstructures of thixoextruded specimens did not show any dendrites or rosette-like structures. The average grain sizes of thixoextruded specimens were smaller than average grain sizes of homogenized specimens.

Microstructural Evolution of AZ31 Mg Wrought Alloy during Partial Remelting for Thixoextrusion

2006 ◽  
Vol 116-117 ◽  
pp. 251-254
Author(s):  
Young Ok Yoon ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Microstructural Evolution ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Holding Time ◽  
Interesting Point ◽  
Grain Sizes ◽  
Partial Remelting ◽  
Average Grain Size ◽  
Holding Temperature

An attempt has been made to investigate feasibility of thixoextrusion for AZ31 Mg wrought alloy through simple partial remelting. Microstructural evolution of AZ31 Mg wrought alloy for thixoextrusion was investigated as functions of isothermal holding temperature and time in the partially remelted semisolid state. The interesting point of this study was that the thixotropic structures of AZ31 Mg wrought alloy without additional pretreatment could be obtained through simple partial remelting. The uniform average grain size and liquid fraction according to the isothermal holding time were very important for the thixoextrusion. Because, it is must be considered on actual extrusion time. The liquid fraction was increased with increasing isothermal holding temperature and time. But, the liquid fraction was almost uniform after 10 min. The average grain size was decreased with increasing isothermal holding temperature. On the other hand, as the holding time increased, the average grain sizes were uniform at 615 and 622. This phenomenon is very useful for thixoextrusion in terms of process control such as actual extrusion time.

Effect of Partial Remelting Procedure on the Microstructural Evolution of 7075 Al Wrought Alloy for Thixoextrusion

2006 ◽  
Vol 116-117 ◽  
pp. 336-339 ◽  
Author(s):  
Hyung Ho Jo ◽  
Young Ok Yoon ◽  
Jin Kyu Lee ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Feasibility Study ◽  
Microstructural Evolution ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Holding Time ◽  
Interesting Point ◽  
Partial Remelting ◽  
Average Grain Size ◽  
Holding Temperature

The feasibility study for thixoextrusion of 7075 Al wrought alloys was carried out with respect to reheating profile, isothermal holding temperature and time during the partial remelting through simple partial remelting. The reheating rates were 40/min and 60/min. The isothermal holding temperatures were controlled at 609, 622, 628 and 632 for 0, 2, 5, 10 and 30 min. The interesting point of this study was that the thixotropic structures of 7075 Al wrought alloy without additional pretreatment could be obtained through simple partial remelting. The average grain size was significantly smaller in the quickly heated specimen. The liquid fraction was increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min is considered very useful for thixoextrusion in terms of actual extrusion time.

Microstructural Control of 7075 Al Wrought Alloys through Thixoextrusion Route

2006 ◽  
Vol 510-511 ◽  
pp. 362-365 ◽  
Author(s):  
Young Ok Yoon ◽  
Hyung Ho Jo ◽  
Jin Kyu Lee ◽  
Dong In Jang ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
High Strength ◽  
Industrial Applications ◽  
High Productivity ◽  
Die Life ◽  
Average Grain Size ◽  
Low Energy Consumption ◽  
Holding Temperature

Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure, extension of the die life, and cost saving owing to its low energy consumption compared with the conventional extrusion processes. Especially, thixoextrusion process is expected to be very effective for hard-to-form materials with high strength. The present study focuses on 7075 Al wrought alloy to investigate the potential industrial applications of the thixoextrusion process. The microstructural evolution of 7075 Al wrought alloy for thixoextrusion was investigated with respect to isothermal holding temperature and time in the partially remelted semisolid state. The results showed that the liquid fraction increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time up to 5min. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding temperature and time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min holding time is considered very useful for thixoextrusion in terms of process control.

Influence of Reheating Profile on Microstructural Evolution of 2024 Al Wrought Alloy for Thixoextrusion

2007 ◽  
Vol 544-545 ◽  
pp. 371-374
Author(s):  
Dong In Jang ◽  
Young Ok Yoon ◽  
Hyung Ho Jo ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Low Energy ◽  
Billet Temperature ◽  
High Productivity ◽  
Main Emphasis ◽  
Average Grain Size ◽  
Low Energy Consumption ◽  
Holding Temperature

Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure and cost saving because of the low energy consumption compared with the conventional extrusion processes. For the thixoextrusion, the low liquid fraction (fL<0.3) should be achieved and also the liquid fraction and average grain size should be uniform according to the reheating profile at the desired low liquid fraction. The main emphasis of this study is to investigate the feasibility of thixoextrusion for 2024 Al wrought alloy without additional pretreatment. The results show that the liquid fraction and average grain size were almost uniform with respect to isothermal holding temperature and time. It was very useful for thixoextrusion in terms of process control such as billet temperature control and actual extrusion time.

Investigation on Dissolving Process of Secondary Phases and Austenitic Grain Growth in a Microalloyed Steel

2014 ◽  
Vol 609-610 ◽  
pp. 509-514 ◽  
Author(s):  
Bin Hao ◽  
Xiao Juan Zhang ◽  
Shao Qiang Yuan ◽  
Guo Li Liang
Keyword(s):  
Microalloyed Steel ◽  
Boundary Migration ◽  
Isothermal Holding ◽  
Low Carbon ◽  
Secondary Phases ◽  
Grain Sizes ◽  
Pinning Effect ◽  
Different Temperatures ◽  
Carbon Microalloyed ◽  
Holding Temperature

The secondary phases such as carbonitrides in the microalloyed steel play very important roles in retarding the austenitic grains growth during reheating. The dissolving process of carbonitrides containing Nb, Ti, Mo will affect the austenitic grain sizes directly. In the present work, the dissolving behaviors of secondary phases in low carbon microalloyed steel during isothermal holding at different temperatures were investigated by electrolytic experiment, carbon extraction replicas, TEM and EDX analysis. Meanwhile, the austenitic grain sizes were measured corresponding to the temperatures. The experimental results indicate that there are two types of carbonitrides in as-forged steel. One is the coarsened Ti-rich precipitates originated from solidification, and the other is the finer Nb-rich particles attributed to strain-induced process. The strain-induced precipitates disappear after being held for 1 h at 1000°C. At 1000~1220 °C, the austenitic grains grow obviously due to rapid dissolving of the carbonitrides containing Nb and Mo. However, some undissolved Nb, Ti carbidenitrides still hinder the grain boundary migration. When the reheating temperature rises to 1270°C, the grain size grows abnormally after being held for 2h. At the holding temperature, few Nb-bearing TiN precipitates can be stable while the pinning effect weakens markedly.

Investigation of Temperature Deformations and Burning of Models from Polymers

2021 ◽  
Vol 316 ◽  
pp. 40-45
Author(s):  
Aksaule A. Mamayeva ◽  
Akerke T. Imbarova ◽  
Marzhan T. Chukmanova
Keyword(s):  
3D Printing ◽  
Isothermal Holding ◽  
Printing Technology ◽  
Temperature Expansion ◽  
3D Printing Technology ◽  
Linear Dimensions ◽  
Temperature Deformations ◽  
Thin Walled ◽  
Subsequent Decomposition ◽  
Holding Temperature

The usage of 3D printing technology SLA and DLP is promising for obtaining casting models. The article presents the results of a study of temperature deformations, developing during the burning of models from polymers “Fun to Do Castable Blend”, “Oh-All! Red” and “Orange Fluor”. In the performance of the experiments, photopolymer models were exposed to an impact of isothermal at temperatures from 50 to 330 °C, and their linear dimensions measured; changes developing on their surface were noted. It is shown that, with an increase of the isothermal holding temperature, the models expand first and narrow later. It has been linked to temperature expansion and subsequent decomposition of the photopolymer. It is shown that the casting molds ,obtained with the usied thin-walled hollow casting models from these photopolymers, are destroyed at the stage of their burning.

Microstructure Evolution and Coarsening Mechanism of 7075 Semi-Solid Aluminum Alloy Pre-Deformed by ECAP Method

2016 ◽  
Vol 256 ◽  
pp. 294-300 ◽  
Author(s):  
Jin Long Fu ◽  
Yu Wei Wang ◽  
Kai Kun Wang ◽  
Xiao Wei Li
Keyword(s):  
Aluminum Alloy ◽  
Solid State ◽  
Ostwald Ripening ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Semi Solid ◽  
Equiaxed Grains ◽  
Kinetics Of

To investigate the influence of refined grains on the microstructure of 7075 aluminum alloy in semi-solid state, a new strain induced melting activation (SIMA) method was put forward containing two main stages: pre-deformation with equal channel angular pressing (ECAP) method and isothermally holding in the semi-solid temperature range. The breaking up and growth mechanisms of the grains and kinetics of equiaxed grains coarsening during the semi-solid holding were investigated. The results showed that the average grain size after ECAP extrusion decreased significantly, e.g., microstructure with average globular diameter less than 5μm was achieved after four-pass ECAP extrusion. Obvious grain coarsening had been found during isothermal holding in the semi-solid state and the roundness of the grains increased with the increasing holding time. The proper microstructure of 66.8μm in diameter and 1.22 in shape factor was obtained under proper soaking condition (at 590°C for 15 min). Two coarsening mechanisms, namely, coalescence in lower liquid fraction and Ostwald ripening in higher liquid fraction contributed to the grain growth process.

scholarly journals Electrodeposition of Co-B/SiC Composite Coatings: Characterization and Evaluation of Wear Volume and Hardness

Coatings ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 279 ◽  
Author(s):  
A. Villa-Mondragón ◽  
A. Martínez-Hernández ◽  
F. Manríquez ◽  
Y. Meas ◽  
J. J. Pérez-Bueno ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Composite Coatings ◽  
Research Work ◽  
Colloidal Suspensions ◽  
Wear Volume ◽  
X Ray Diffraction ◽  
Homogeneous Composition ◽  
Different Content ◽  
Sic Coatings ◽  
Hardness Values

In this research work, Co-B/SiC composite coatings were synthesized by electrochemical deposition from colloidal suspensions with different content of SiC. The Co-B/SiC films obtained were heat treatment at 350 °C. The composition, morphology, and structure of the Co-B/SiC composite coatings were analyzed using glow discharge spectrometry (GDS), scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Hardness and tribological properties were also studied. The results showed that an increase in the SiC concentration in the colloidal suspensions resulted in both an increase in the SiC content and a decrease in the B content in the obtained Co-B/SiC coatings. The Co-B/SiC coatings were adherent, glossy, and soft, and exhibited a homogeneous composition in all thicknesses. Besides, an increase in the SiC particle content of the Co-B/SiC composite coating from 0 to 2.56 at.% SiC reduced the hardness of the film from 680 to 360 HV and decreased the wear volume values from 1180 to 23 μm3 N−1 m−1, respectively (that is, the wear resistance increased). Moreover, when the Co-B/SiC coatings with SiC content ranging from 0 to 2.56 at.% SiC were subjected to a heat treatment process, the obtained coating hardness values were in the range of 1200 to 1500 HV, and the wear volume values were in the range of 382 to 19 μm3 N−1 m−1.

Nanostructure Evolution of ZnO in Ultra-fast Microwave Sintering

2011 ◽  
Vol 691 ◽  
pp. 65-71 ◽  
Author(s):  
Rodolfo F. K. Gunnewiek ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Grain Size ◽  
Zinc Oxide ◽  
Grain Growth ◽  
Microwave Sintering ◽  
High Heating Rate ◽  
Heating Rates ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Conventional Sintering ◽  
Holding Temperature

Grain growth is inevitable in the sintering of pure nanopowder zinc oxide. Sintering depend on diffusion kinetics, thus this growth could be controlled by ultra-fast sintering techniques, as microwave sintering. The purpose of this work was to investigate the nanostructural evolution of zinc oxide nanopowder compacts (average grain size of 80 nm) subjected to ultra-rapid microwave sintering at a constant holding temperature of 900°C, applying different heating rates and temperature holding times. Fine dense microstructures were obtained, with controlled grain growth (grain size from 200 to 450nm at high heating rate) when compared to those obtained by conventional sintering (grain size around 1.13µm), which leads to excessively large average final grain sizes.

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