Microstructural Evolution of Eutectic Al-Si Alloys Produced by Semi-Continuously DC Casting during Heating and Hot-Rolling

2010 ◽  
Vol 146-147 ◽  
pp. 1289-1292
Author(s):  
Tao Hong ◽  
Gang Zhao ◽  
Ni Tian ◽  
Fu Xiao Yu ◽  
Liang Zuo
Keyword(s):  
Uniform Distribution ◽  
Microstructural Evolution ◽  
Compression Ratio ◽  
Hot Rolling ◽  
Direct Chill ◽  
Optical Microstructure ◽  
Eutectic Si ◽  
Dc Casting ◽  
Size And Morphology ◽  
Hot Plasticity

Semi-continuously direct chill (DC in short) casting was carried out to modify the size and morphology of eutectic Si particles in eutectic Al-Si alloy. Successively, the size, morphology, distribution characters of eutectic Si particles and the hot plasticity ability of the alloy during heating and hot-rolling were investigated by the observation of optical microstructure characterization and the rolling of wedge bar. The results show that the eutectics in the eutectic Al-Si alloy can be remarkably fined by semi-continuously DC cast. The eutectic Si phase particles will coarsen and spheroidize after holding at 480°C for 2h, which enables eutectic Al-Si alloy to possess excellent hot plasticity free of cracked edge with compression ratio of rolling up to 85% by single pass. Though little difference on the size of spheroidized Si particles during hot rolling can be observed, uniform distribution of the Si particles can be obtained by hot rolling with compression ratio of 85%.

Deformability of Eutectic Al-Si Alloys Produced by Semi-Continuously DC Casting during Hot-Rolling

2012 ◽  
Vol 706-709 ◽  
pp. 436-440 ◽  
Author(s):  
Tao Hong ◽  
Gang Zhao ◽  
Ni Tian ◽  
Fu Xiao Yu ◽  
Liang Zuo
Keyword(s):  
Compression Ratio ◽  
Hot Rolling ◽  
Direct Chill ◽  
Single Pass ◽  
Eutectic Si ◽  
Dc Casting ◽  
Hot Rolled ◽  
Rolling Deformation ◽  
Hot Plasticity

The deformability and the microstructures of Al-12.2Si-0.6Mg alloy during hot-rolling were investigated by means of rolling the specimens of wedge bars with length of 180mm and width of 30mm, which had front thickness of 5mm and back thickness of 44mm.The wedge bars were cut from the ingots of the Al-12.2Si-0.6Mg alloy by the semi-continuously direct chill (DC in short) casting. The specimens of wedge bars were hot-rolled following holding between 410°Cand 480°C for different time. The results show that the size, morphology, distribution characters of eutectic Si particles in the Al-12.2Si-0.6Mg alloy can be remarkably modified by semi-continuously DC casting, which consists of coarse ribbon-like Si-particles with less than 5μm in length and 1μm in width and quite a lot eutectic phases of less than 0.4μm in size and space. The results also show that the ingots of the Al-12.2Si-0.6Mg alloy by the semi-continuously DC casting can possess excellent deformability during hot-rolling if the extent of heating is provided over 440°C for 60min and 410°C for 120min, and they cannot emerge cracked edges with the compression ratio of 85% by single-pass rolling. Their hot-plasticity depends on the size and space between eutectic phases in the ingots. Hot-rolling deformation makes ribbon-like Si phases in them crack and spheroidize, and then results in the sizes of coarse Si particles tending to be consistent.

Role of Grain Refining in Macrosegregation upon Direct Chill Casting of AA 2024 Round Billet

2006 ◽  
Vol 519-521 ◽  
pp. 1841-1846 ◽  
Author(s):  
Ravi Nadella ◽  
Dmitry G. Eskin ◽  
Laurens Katgerman
Keyword(s):  
Cross Section ◽  
Direct Chill ◽  
Al Alloys ◽  
Grain Refining ◽  
Negative Segregation ◽  
Aa 2024 ◽  
Dc Casting ◽  
Size And Morphology ◽  
Equiaxed Grains

The addition of grain refiners during industrial direct chill (DC) casting of aluminum billets promotes formation of smaller equiaxed grains with obvious advantages. However, the role of grain refining in the extent of macrosegregation in DC cast Al alloys is still unclear. This is particularly evident in the case of commercial aluminum alloys with various alloying elements. In this work, the structure and associated macrosegregation patterns in DC cast AA 2024 (Al–Cu–Mg) aluminum alloy billets were studied at different casting speeds. The concentration profiles of Cu and Mg, measured along the billet diameter, showed an expected negative segregation in the center and close to the surface. The severity of segregation increases at a higher casting speed. On the other hand, grain refining does not seem to have any dramatic effect on the macrosegregation patterns. The experimental results are correlated with microstructural observations such as grain size and morphology and the occurrence of “floating” grains across the cross-section of the billet.

A Roll Caster to Cast Clad Strip

2013 ◽  
Vol 554-557 ◽  
pp. 1902-1909 ◽  
Author(s):  
Toshio Haga ◽  
Hiroshi Tsuge ◽  
Shinji Kumai ◽  
Hisaki Watari
Keyword(s):  
Melting Point ◽  
Hot Rolling ◽  
Direct Chill ◽  
Al Alloys ◽  
Mg Alloy ◽  
Lower Melting ◽  
Lower Melting Point ◽  
Dc Casting ◽  
Twin Roll Caster ◽  
Twin Roll

A tandem-type roll caster that can cast a three-layered clad strip was developed by mounting one twin roll caster on another twin roll caster. In this caster, the base strip is cast by the upper twin roll caster, and the overlay strips are cast by the lower caster. The three strips are metallurgically bonded by the lower caster. This study investigated three aspects of this caster. First, the clad ratio could be controlled by the solidification lengths of strips from the upper and lower twin roll casters, and a clad ratio of 1:8:1 was attained. Second, although it is known that fabrication of clad strips from Al-Mg alloy and other Al alloys is very difficult, the clad strip with the Al-Mg alloy as the base strip or the overlay strip could be cast. Finally, by adding scrapers, the caster could cast the clad strip with a base strip having a lower melting point than the overlay strip. Element strips of the clad strip are made by many processes, such as direct chill (DC) casting, scraping of the ingot surface, heat treatment, hot rolling, and cold rolling. Typically, surface treatment and hot rolling are used to clad the strips. Since many processes are required, clad strips require consume much energy. Therefore, producing clad strips is expensive. A vertical-type tandem twin roll caster was developed to cast clad strips. This caster has the advantages of process saving and energy saving, and so can fabricate economical clad strips. In the fabrication of clad strips, control of the clad ratio is very important. In the brazing sheet for automobile radiators, the base strip is made from AA3003 and the overlay strips are made from AA4045, and the clad ratio is usually 1:8:1. In the present study, a clad strip with a clad ratio of 1:8:1 was attained. The cladding by hot rolling of Al-Mg and other aluminum alloys, which is considered to be a very difficult process, was also investigated. Clad strips with either a base strip or an overlay strip of an Al-Mg alloy were cast by the roll caster. Although the cladding was not easy, the Al-Mg alloy could be cast into the clad strip. In addition, a clad strip with a base strip having a lower melting point than that of the overlay strip was investigated. Such cladding cannot be cast by the vertical-type tandem twin roll caster as mentioned above because the base strip is re-melted from the heat of the overlay strips. In the present study, a scraper was developed and adopted to cast a clad strip with a base having a lower melting point than that of the overlay strips. This type of clad strip could be cast because the scrapers prevented the re-melting of the base strip. In this paper, these three aspects of fabrication are reported.

Effects of Casting Conditions on End Product Defects in Direct Chill Casted Hot Rolling Ingots

2016 ◽  
pp. 185-193 ◽  
Author(s):  
Arda Yorulmaz ◽  
Çağlar Yüksel ◽  
Eraz Erzi ◽  
Derya Dispinar
Keyword(s):  
Hot Rolling ◽  
Direct Chill

Numerical simulation and experiment validation of level-pour direct-chill casting of A390 alloy hollow billets under different feeding schemes

2016 ◽  
Vol 26 (6) ◽  
pp. 1871-1888 ◽  
Author(s):  
Kesheng Zuo ◽  
Haitao Zhang ◽  
Ke Qin ◽  
Jianzhong Cui
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Three Dimensional ◽  
Direct Chill ◽  
Melt Flow ◽  
Content Type ◽  
Primary Si ◽  
Hollow Billet ◽  
Dc Casting ◽  
A390 Alloy

Purpose – The purpose of this paper is to study the effect of feeding scheme on melt flow and temperature field during the steady-state of level-pour direct-chill (DC) casting of A390 alloy hollow billet and optimize the design of feeding scheme. Design/methodology/approach – Melt flow and temperature field are investigated by numerical simulation, which is based on a three-dimensional mathematical model and well verified by experiments. Findings – The numerical results reveal that both melt flow and temperature field are obviously affected by the feeding scheme. The homogeneity of melt flow and temperature field in hollow billet with the feeding scheme of modified four inlets are better than the other feeding schemes. Experimental results show that crack can be eliminated by increasing the number of feeding inlets. The primary Si size appears unaffected while the distribution of primary Si particles is highly affected by the change of feeding scheme. Only with the feeding scheme of modified four inlets can fine and uniformly distributed primary Si particles be achieved. Practical implications – The paper includes implications for the design of feeding scheme in level-pour DC casting of hollow billet for practical use. Originality/value – This paper develops different feeding schemes for level-pour DC casting of hollow billet and optimizes the design of feeding scheme.

Modelling of the Metal/Mould Interactions in the DC Casting Process for Aluminium and Magnesium

2010 ◽  
Vol 654-656 ◽  
pp. 783-786 ◽  
Author(s):  
Arvin Prasad ◽  
Ian F. Bainbridge
Keyword(s):  
Heat Transfer ◽  
Casting Process ◽  
Direct Chill ◽  
Heat Extraction ◽  
Small Scale ◽  
Wall Region ◽  
Wall Heat Transfer ◽  
Mould Wall ◽  
Dc Casting ◽  
Basic Features

The process of direct chill (DC) casting of aluminium and magnesium alloys is regarded as a mature technology. The thrust of more recent work to understand and upgrade the technology has been centred on developing models of the process, the most advanced of which (e.g., Alsim and Calcasoft) have been used to examine what may be considered macro-features of the process (macro-segregation, hot cracking, etc.). These models, being macroscopic, rarely elaborate on the role of mould-wall heat transfer in the DC casting process. As part of the work on DC casting being conducted at CAST, for the investigation of small scale features of the process (e.g. heat extraction through the mould wall), a 2D finite Difference model of the process near the mould-wall region has been developed. The basic features of the model are described and initial results outlined.In particular, the effect of mould-wall heat transfer on the solid shell formed during the steady state regime of DC casting will be presented.

DC Casting, Deformation and Strengthening of Al-Si Alloys

2012 ◽  
Vol 706-709 ◽  
pp. 186-193 ◽  
Author(s):  
Liang Zuo ◽  
Fu Xiao Yu
Keyword(s):  
Mechanical Properties ◽  
Direct Chill ◽  
Cast State ◽  
The Poor ◽  
Low Thermal Expansion ◽  
Cast Alloys ◽  
Superior Mechanical Properties ◽  
Deformation And Heat Treatment ◽  
Dc Casting ◽  
Strength And Ductility

Al-Si alloys are widely used as cast alloys for their excellent castability, low thermal expansion coefficient, good wear resistance and corrosion resistance properties. However, the poor ductility of these alloys, caused by the presence of coarse and non-deformable Si phase in the as-cast state, has inhibited their applications as wrought materials. Recently, a process based on traditional technologies, i.e., direct chill (DC) casting followed by hot deformation and heat treatment, has been developed for potential mass production of wrought Al-Si alloys with superior mechanical properties in view of their strength and ductility. In this work, the microstructural evolutions of DC cast Al-Si alloys involved in solidification, recrystallization and precipitation during the processing are highlighted, aiming at understanding the correlations between the microstructures and the mechanical properties.

Application Research of a New Coupling Stirring on DC Casting Process for Large-Sized Aluminum Ingots

2015 ◽  
Vol 817 ◽  
pp. 48-54 ◽  
Author(s):  
Hai Jun Wang ◽  
Jun Xu ◽  
Zhi Feng Zhang ◽  
Bo Liang ◽  
Ming Wei Gao
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Casting Process ◽  
Direct Chill ◽  
Application Research ◽  
Center Position ◽  
Composition Segregation ◽  
Dc Casting ◽  
The Difference ◽  
7075 Alloy

A new coupling stirring technology was proposed and used to prepare direct chill (DC) ingots. Ingots of 7075 alloy were produced by a process of normal direct chill (NDC) casting and coupling-stirring direct chill (CDC) casting, respectively. The effect of the technology on the microstructures, composition segregation and mechanical properties of the ingots was investigated. The results showed that the temperature variation in the CDC casting process was more uniform than that in the NDC casting process. The grain of the CDC ingots was finer and more spherical than the grain of NDC ingots. The grain size at the edge, 1/2 radius, and center position in CDC ingot decrease by 28%, 22%, and 24% comparing with the grain size of the corresponding positions of NDC ingot, respectively. The billets with higher performance and lower macro-segregation were obtained in case of CDC. The flow stresses and the difference in different positions of DC ingots measured at Gleeble-1500D thermo-mechanical simulator decreased obviously when the coupling stirring technology is used in the casting process.

scholarly journals Effect of CaCl2 on Microstructure of Calciothermic Reduction Products of Ti2O3 to Prepare Porous Titanium

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 698 ◽  
Author(s):  
Guobo Yang ◽  
Baoqiang Xu ◽  
Heli Wan ◽  
Fengkang Wang ◽  
Bin Yang ◽  
...  
Keyword(s):  
Particle Size ◽  
Uniform Distribution ◽  
Reduction Process ◽  
Porous Titanium ◽  
Surface Zone ◽  
Calciothermic Reduction ◽  
Particle Size And Morphology ◽  
Ti Particles ◽  
Size And Morphology ◽  
Titanium Structure

The compound CaCl2 plays a significant role in the process of direct calciothermic reduction of Ti2O3 to prepare porous titanium. In this paper, the effect of CaCl2 on reduction products by calciothermic reduction of Ti2O3 was investigated. Results show that the distribution of CaCl2 in reduction preform influences particle size and morphology differences in reduction products both on the surface and the inside. The CaCl2 is transferred to the surface of the Ti2O3 preform due to its volatilization before and throughout reduction. The content of CaCl2 in the surface zone of Ti2O3 preform is significantly higher than that in the interior during the reduction process, contributing to the formation of large Ti particles with a smooth shape on the surface, and small Ti particles with inherited morphology of Ti2O3 inside. More CaCl2 causes the aggregation of Ti particles to form large Ti particles which are advantageous as they connect and form a more solid porous titanium structure. The presence of a small amount of CaCl2 in the interior also results in the coexistence of small Ti and CaO particles, forming a loose structure with uniform distribution.

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