scholarly journals Multimodal Microstructure and Mechanical Properties of AZ91 Mg Alloy Prepared by Equal Channel Angular Pressing plus Aging

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 763 ◽  
Author(s):  
Zhenquan Yang ◽  
Aibin Ma ◽  
Huan Liu ◽  
Jiapeng Sun ◽  
Dan Song ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Magnesium Alloys ◽  
High Strength ◽  
Cost Effective ◽  
Back Stress ◽  
Grain Structure ◽  
Mg Alloy ◽  
Precipitation Strengthening ◽  
Processing Route ◽  
Good Ductility

Developing cost-effective magnesium alloys with high strength and good ductility is a long-standing challenge for lightweight metals. Here we present a multimodal grain structured AZ91 Mg alloy with both high strength and good ductility, prepared through a combined processing route of low-pass ECAP with short-time aging. This multimodal grain structure consisted of coarse grains and fine grains modified by heterogeneous precipitates, which resulted from incomplete dynamic recrystallization. This novel microstructure manifested in both superior high strength (tensile strength of 360 MPa) and good ductility (elongation of 21.2%). The high strength was mainly attributed to the synergistic effect of grain refinement, back-stress strengthening, and precipitation strengthening. The favorable ductility, meanwhile, was ascribed to the grain refinement and multimodal grain structure. We believe that our microstructure control strategy could be applicable to magnesium alloys which exhibit obvious precipitation strengthening potential.

scholarly journals Accelerated discovery of high-strength aluminum alloys by machine learning

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Jiaheng Li ◽  
Yingbo Zhang ◽  
Xinyu Cao ◽  
Qi Zeng ◽  
Ye Zhuang ◽  
...  
Keyword(s):  
Machine Learning ◽  
Aluminum Alloys ◽  
Mechanical Performance ◽  
High Strength ◽  
Cost Effective ◽  
Alloy System ◽  
Processing Route ◽  
Specific Strength ◽  
Cu Alloy ◽  
High Strength Aluminum Alloys

Abstract Aluminum alloys are attractive for a number of applications due to their high specific strength, and developing new compositions is a major goal in the structural materials community. Here, we investigate the Al-Zn-Mg-Cu alloy system (7xxx series) by machine learning-based composition and process optimization. The discovered optimized alloy is compositionally lean with a high ultimate tensile strength of 952 MPa and 6.3% elongation following a cost-effective processing route. We find that the Al8Cu4Y phase in wrought 7xxx-T6 alloys exists in the form of a nanoscale network structure along sub-grain boundaries besides the common irregular-shaped particles. Our study demonstrates the feasibility of using machine learning to search for 7xxx alloys with good mechanical performance.

Third generation of advanced high-strength steels: Processing routes and properties

2016 ◽  
Vol 233 (2) ◽  
pp. 209-238 ◽  
Author(s):  
Tarun Nanda ◽  
Vishal Singh ◽  
Virender Singh ◽  
Arnab Chakraborty ◽  
Sandeep Sharma
Keyword(s):  
Automobile Industry ◽  
Second Generation ◽  
Low Cost ◽  
High Strength Steels ◽  
High Strength ◽  
Cost Effective ◽  
Processing Route ◽  
Third Generation ◽  
Specific Strength ◽  
Advanced High Strength Steels

The automobile industry is presently focusing on processing of advanced steels with superior strength–ductility combination and lesser weight as compared to conventional high-strength steels. Advanced high-strength steels are a new class of materials to meet the need of high specific strength while maintaining the high formability required for processing, and that too at reasonably low cost. First and second generation of advanced high-strength steels suffered from some limitations. First generation had high strength but low formability while second generation possessed both strength and ductility but was not cost effective. Amongst the different types of advanced high-strength steels grades, dual-phase steels, transformation-induced plasticity steels, and complex phase steels are considered as very good options for being extended into third generation advanced high-strength steels. The present review presents the various processing routes for these grades developed and discussed by different authors. A novel processing route known as quenching and partitioning route is also discussed. The review also discusses the resulting microstructures and mechanical properties achieved under various processing conditions. Finally, the key findings with regards to further research required for the processing of advanced high-strength steels of third generation have been discussed.

Comparative Study on TiH2 and CaCO3 for Fabrication of Mg Alloy Foams

2008 ◽  
Vol 569 ◽  
pp. 273-276 ◽  
Author(s):  
Chang Hwan Seo ◽  
M. J. Jeong ◽  
In Young Jung ◽  
Bo Young Hur
Keyword(s):  
Metal Foam ◽  
High Strength ◽  
Cost Effective ◽  
Decomposition Temperature ◽  
Mg Alloy ◽  
New Materials ◽  
Alloying Element ◽  
Blowing Agent ◽  
Economic View ◽  
Cost Effective Method

Aluminum alloy foams, new materials belonging to a special class of porous materials, have been prepared using melt foaming method. Silicon was chosen alloying element due to its low density, high strength, effective casting and reduced shrinkage. Melt foaming method is cost-effective method to fabricate metal foam. Usually, TiH2 is applied to blowing agent, but its cost is high. CaCO3 is one of candidates to substitute TiH2 in the economic view-point. For the comparison of formability, Mg alloy foams were prepared by TiH2 and CaCO3. However, the decomposition temperature of CaCO3 is higher than that of TiH2. This paper will be discussed on the possible usage of CaCO3 in the Al melt.

Precipitation Strengthening of Micro-Alloyed Steels Thermo-Mechanically Processed by Ultra Fast Cooling

2012 ◽  
Vol 706-709 ◽  
pp. 2320-2325 ◽  
Author(s):  
Zhen Yu Liu ◽  
Shuai Tang ◽  
Xiao Hui Cai ◽  
Guo Dong Wang
Keyword(s):  
Grain Refinement ◽  
Hot Rolling ◽  
Precipitation Strengthening ◽  
Processing Route ◽  
Accelerated Cooling ◽  
Pressurized Water ◽  
Great Loss ◽  
Ultra Fast Cooling ◽  
Dislocation Hardening ◽  
Fast Cooling

Thermo-mechanical Controlled Processing (TMCP) is one of the greatest achievements in steel industry in the 20th century, which, however, depends too much upon low temperature rolling for the refinement of austenite grains, causing great loss in terms of productivity. To overcome this disadvantage, a new processing route with ultra fast cooling as the core has been proposed, and pilot rolling and industrial trials were carried out. As compared to conventional accelerated cooling, the ultra fast cooling can achieve cooling rate up to 300°C/s for 3 mm thick strip and highly homogeneous cooling by the pressurized water spraying. In the present work, the metallurgical backgrounds for ultra fast cooling in thermo-mechanical processing were studied and elucidated. By the pilot hot rolling experiments with a lean composition of a typical 600 MPa grade high strength steel, it has been found that the application of ultra fast cooling (UFC) at the exit of hot rolling mills can improve the strength by as much as 100 MPa as compared to the conventional TMCP. The strengthening mechanism lies in that the ultra fast cooling immediately after hot rolling may further improve the strengthening effects by precipitation, grain refinement, and dislocation hardening. The theoretical calculations and experiments indicate that the grain refinement, dislocation hardening, and precipitation in the TMCP with in-front UFC have caused the strength increments of 36, 34 and 54 MPa over the conventional TMCP with ACC, respectively. The microstructure characterization showed that the density of high angle grain boundaries had been increased, and the average size of precipitates had been reduced from about 34 nm to 10 nm with the cooling pattern changing from ACC to the application of UFC. The theoretical estimation indicates that when the cooling profile is changed from the conventional ACC to UFC+ACC, and to UFC, precipitation strengthening accounts for more and more strength increment in the improved strength of hot rolled micro-alloyed steels.

Equal Channel Angular Pressing of Al Alloy AA2219

2009 ◽  
Vol 67 ◽  
pp. 53-58
Author(s):  
V. Anil Kumar ◽  
M.K. Karthikeyan ◽  
Rohit Kumar Gupta ◽  
P. Ramkumar ◽  
P.P. Sinha
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
High Strength ◽  
Dark Field ◽  
Grain Structure ◽  
Al Alloy ◽  
Angular Pressing

Severe plastic deformation processes (SPD) are gaining importance as advanced materials processing techniques and hold immense potential in obtaining ultra fine-grained high strength materials. Among the SPD techniques, Equal channel angular pressing (ECAP) has its own merits to produce materials with ultra fine grains in bulk with better mechanical properties. The material deforms with high level of plastic strain inside the channel resulting in grain refinement of the output material with improvement in mechanical properties. A very viable die configuration was conceptualized and die was made with 1200 channel angle. Processing of 25 mm dia. of Al alloy AA2219 at room temperature was successfully carried out and grain refinement was observed. The mechanism of grain refinement has been studied using optical and transmission electron microscopy (TEM). It was observed that low energy dislocation structure (LEDS) forms concurrently with sub-grain structure due to dislocation rearrangements, which provide stability to the evolving sub-grain structure. Dislocation mobility is hindered by the presence of precipitates and / or intermetallic dispersoids present in the matrix and results in presence of dislocations in grain interiors. The pile up of dislocations at intermetallic dispersoids was confirmed from the dark field TEM micrographs. Present paper describes the experimental procedure and followed to attain severe plastic deformation through ECAP. Increase in hardness as well as refinement in the grain size after 5-passes have been discussed in light of extensive optical and TEM. The mechanisms of grain refinement to achieve nano-grained structure and strengthening accrued from the grain refinement through ECAP has been discussed.

Processing, Superplastic Properties and Friction Stir Welding of Fine-Grained AZ31, AZ91, AE42 and QE22 Magnesium Alloys

2016 ◽  
Vol 838-839 ◽  
pp. 220-224 ◽  
Author(s):  
Talant Ryspaev ◽  
M. Janecek ◽  
Robert Kral ◽  
Volker Wesling ◽  
Lothar Wagner
Keyword(s):  
Friction Stir Welding ◽  
Grain Refinement ◽  
Magnesium Alloys ◽  
Mechanical Treatment ◽  
Base Material ◽  
Rate Sensitivity ◽  
Grain Structure ◽  
Friction Stir ◽  
Thermo Mechanical Treatment ◽  
Superplastic Properties

The grain refinement after thermo-mechanical treatment (TMT) was investigated in AZ91, AE42, und QE22 magnesium alloys. The optimal over-aging temperature was determined to be 300 °C in the case of AZ91 and AE42 alloys and 350 °C for QE22 alloy. After optimized TMT, the average grain sizes were 13.5 µm (AE42), 11.1 µm (AZ91) and 1.9 µm (QE22). The QE22 alloy exhibited the superior superplastic properties, with maximum elongation to failure 750 % and strain rate sensitivity parameter m=0.73. The Friction Stir Welding showed that the original base material grain structure of the alloys AZ31 and AZ91 replaced by ultrafine grains in the stir zone. The purpose of the present paper is to present the results of the grain refinement in magnesium alloys by thermo mechanical treatment and stir welding.

Combined Strengthening-Toughening Technology of High Property Titanium Alloys for Aviation Uses in China

2015 ◽  
Vol 727-728 ◽  
pp. 158-162
Author(s):  
Zhi Shou Zhu ◽  
Xin Nan Wang ◽  
Guo Qiang Shang ◽  
Yue Fei ◽  
Han Qing Yu
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloys ◽  
Grain Refinement ◽  
Lamellar Structure ◽  
High Strength ◽  
Grain Structure ◽  
High Ductility ◽  
High Property ◽  
Weave Structure ◽  
Static Mechanical

Combined strengthening-toughening technologies of several high property titanium alloys, such as TC4-DT, TC6, TC18, TC21 for aviation uses, have been studied via purification, quasi-b heat treatment, quasi-b forging and grain refinement. The effects of microstructure parameters of lamellar structure, basket-weave structure, refined grain structure etc. on the comprehensive mechanical properties of titanium alloys have been analyzed. The results have shown that, to acquire highly comprehensive static mechanical properties and excellent damage tolerance properties, quasi-b treatment and purification processing should be used for medium strength titanium alloys to get high ductility lamellar structure, while quasi-b forging processing be utilized for high strength titanium alloys to obtain high ductility basket-weave structure. Grain refinement processing is very necessary for both the strength levels of titanium alloys.

scholarly journals Enhancing the Mechanical Properties of AZ80 Alloy by Combining Extrusion and Three Pass Calibre Rolling

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 249 ◽  
Author(s):  
Shuaiju Meng ◽  
Hui Yu ◽  
Jun Zhou ◽  
Haisheng Han ◽  
Yongyan Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Grain Structure ◽  
Processing Route ◽  
Bimodal Microstructure ◽  
Basal Texture ◽  
Micro Scale ◽  
Uniform Microstructure ◽  
Novel Processing ◽  
Az80 Alloy

An AZ80 alloy with ultra-high strength and good ductility has been successfully prepared by a novel processing route of combining extrusion and caliber rolling. The caliber rolled (CRed) AZ80 alloy has a necklace grain structure with ultrafine dynamic recrystallized (DRXed) grains formed around the micro-scale deformed grains, which is remarkably different from the uniform microstructure of as-extruded sample free from caliber rolling. In addition, both the deformed region and the DRXed part in CRed AZ80 alloy exhibit more random basal texture than that of the as-extruded sample. Furthermore, the CRed AZ80 alloy demonstrates an excellent comprehensive mechanical property with the ultimate tensile strength of 446MPa and elongation of 13%, respectively. These good mechanical properties of CRed AZ80 alloy can be attributed to the synthetic effects of necklace bimodal microstructure containing ultra-fine grains, profuse Mg17Al12 precipitates, and the modified texture.

Microstructure and Tensile Properties of Magnesium Alloy Containing Quasicrystallines Processed by Equal-Channel-Angular-Extrusion

2005 ◽  
Vol 475-479 ◽  
pp. 469-472 ◽  
Author(s):  
Ming Yi Zheng ◽  
Xiao Guang Qiao ◽  
Shi Wei Xu ◽  
Kun Wu ◽  
Shigeharu Kamado ◽  
...  
Keyword(s):  
Grain Size ◽  
Magnesium Alloy ◽  
Tensile Properties ◽  
Grain Refinement ◽  
Equal Channel Angular Extrusion ◽  
High Strength ◽  
Good Combination ◽  
Mg Alloy ◽  
High Ductility ◽  
Angular Extrusion

Equal channel angular extrusion (ECAE) was performed on as-cast ZW1101 (Mg-11wt%Zn- 0.9wt%Y) Mg alloy containing quasicrystallines. The grain size of α-Mg was effectively refined, and coarse eutectic quasicrystalline phases were broken and dispersed in the alloy by ECAE. The alloy processed by ECAE exhibited a good combination of high strength and high ductility, which is due to the grain refinement and fine dispersed quasicrystallines in the alloy.

scholarly journals The Impact of Isothermal Treatment on the Microstructural Evolution and the Precipitation Behavior in High Strength Linepipe Steel

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 634
Author(s):  
Yong Tian ◽  
Hongtao Wang ◽  
Xiaoning Xu ◽  
Zhaodong Wang ◽  
R.D.K. Misra ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
High Strength ◽  
Interparticle Spacing ◽  
Grain Structure ◽  
Granular Bainite ◽  
Precipitation Strengthening ◽  
Isothermal Treatment ◽  
Strengthening Effect ◽  
Precipitation Behavior ◽  
The Impact

Isothermal treatment affects the microstructural evolution and the precipitation behavior of high-strength low alloy (HSLA) steels. In this regard, thermal simulation of different isothermal treatment temperatures was adopted by using a thermomechanical simulator. The results showed that hardness reached the maximum value at 600 °C holding temperature, which was related to a finer grain structure and granular bainite. The strengthening effect of precipitates was remarkable due to the combination of small particle size and small interparticle spacing. It is presumed that the precipitation started after 600 s at 600 °C. Precipitation strengthening continued to exist, even though coarsening of ferrite grains led to softening phenomena when the specimen was isothermally held at 750 °C, which led to relatively high hardness. The precipitates were fcc (Ti, Nb) (N, C) particles, and belonged to MX-type precipitates. Average size of precipitates increased from 3.14 to 4.83 nm when the specimens were isothermally held between 600 °C and 800 °C. Interparticle spacing of precipitates also increased with increasing isothermal treatment temperatures. These led to a reduction in precipitation strengthening. At the same time the polygonal ferrite content increased and ferrite grain size got larger, such that the hardness decreased continuously.

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