Kinetics of Coarsening and Solid Sphericity during Reheating of Ductile Iron and Al Alloys

Reheating process in the semi-solid state is a very important step in the thixoforming process. In this research semi-solid ductile cast iron and Al alloys (Al-2.5Si, Al356) prepared by inclined plate method, were reheated to examine the effect of reheating conditions on the microstructure and coarsening kinetics of the alloys. For ductile cast iron, solid fraction at different reheating temperatures and holding times was obtained and based on these results the optimum reheating temperature range was determined. In the case of Al alloys increase of holding time in the semi-solid state, leads to increase of liquid fraction, solid grain size and improvement of sphericity of solid particles. In addition, the results show that coarsening kinetics of microstructures of both alloys during reheating was diffusion controlled and can be mostly treated by Ostwald ripening theory.

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

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.256.294 ◽

2016 ◽

Vol 256 ◽

pp. 294-300 ◽

Cited By ~ 4

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.

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Effect of Slope Plate Variables and Reheating on the Semi-Solid Structure of Al Alloys

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.116-117.201 ◽

2006 ◽

Vol 116-117 ◽

pp. 201-204 ◽

Cited By ~ 5

Author(s):

S. Ashouri ◽

Mahmoud Nili-Ahmadabadi

Keyword(s):

Al Alloys ◽

Solid Particles ◽

Pouring Temperature ◽

Casting And Solidification ◽

Main Effect ◽

Solid Region ◽

Semi Solid ◽

The Cost ◽

Kinetics Of

Semi-solid forming (SSF) involves alloys with non-dendrite microstructure that contain spherical solid particles in the liquid matrix. This process is generally divided into three main steps: feedstock manufacturing, reheating and forming. Feedstock has the main effect on the cost and quality of product. Many researches have been carried out to reduce the cost of feedstock manufacturing. Slope plate is a simple semi-solid process that can reduce the cost of feedstock. In this study a Cu plate with water and without water circulation was used to investigate the effect of pouring temperature, cooling rate during casting and solidification in the mold on the microstructure. Cast ingots with optimized microstructure were reheated in various time and temperatures in semi-solid region to obtain kinetics of globularization and solid grain growth.

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Effect of slope plate variable and reheating on the semi-solid structure of ductile cast iron

Tsinghua Science & Technology ◽

10.1109/tst.2008.6071860 ◽

2008 ◽

Vol 13 (2) ◽

pp. 147-151 ◽

Cited By ~ 3

Author(s):

M. Nili-Ahmadabadi ◽

F. Pahlevani ◽

P. Babaghorbani

Keyword(s):

Cast Iron ◽

Ductile Cast Iron ◽

Solid Structure ◽

Semi Solid

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Model of Solid State Transformations of Ductile Cast Iron GJS-600

Advances in the State of the Art of Fire Testing ◽

10.1520/stp49156s ◽

2010 ◽

pp. 295-295-12

Author(s):

V. Runser ◽

V. Schulze

Keyword(s):

Cast Iron ◽

Solid State ◽

Ductile Cast Iron

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Development of Adapted Heat Treatments for Steels out of the Semi-Solid State after Thixoforming

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.141-143.695 ◽

2008 ◽

Vol 141-143 ◽

pp. 695-700 ◽

Cited By ~ 4

Author(s):

Sebastian Dziallach ◽

Wolfgang Püttgen ◽

Wolfgang Bleck

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Solid State ◽

Treatment Strategies ◽

Solid Particles ◽

High Wear Resistance ◽

Hard Material ◽

Current State ◽

Suitable Heat Treatment ◽

Semi Solid

The process of thixoforming incorporates a series of forming processes in the semi-solid state, which can be categorized between the conventional processes of forging and casting and combines the advantages of these processes. Thixoforming of steels in the semi-solid state, requires round, solid particles (globulites) in a liquid matrix which is deformed with low forming forces. In order to achieve laminar material flow and to produce segregation-free components, the material must fulfil diverse criteria. First, the melting interval should be as large as possible for an easy temperature regulation. Next, low solidus and liquidus temperatures are advantageous regarding tool loading. Additionally, thixoformable steels should show a melting behaviour that is finegrained and globular. Furthermore, these steels should possess low contents of intraglobular liquid phase fractions. This paper gives a survey of the current state of steel Thixoforming and deals with the development of adaptive heat treatment strategies. Regarding the structure formation and the development of suitable heat treatment strategies, the once semi-solid state yields new structures that can be applied in ways not previously possible with conventional hardening processes. New microstructures and up to date unknown better mechanical properties can be adjusted with an optimised heat treatment strategy. By this, new fields of application for thixo-materials can be entered and also advanced procedures for special applications can be established. For example the steel X210CrW12 leads to a very hard material with high wear-resistance, which can be used at higher temperatures than the conventional hardened material. In general, new generic microstructures after thixoforming results in unexpected favourable mechanical properties. Problems arise with respect to segregation and pores which resulting in inhomogeneous property distributions.

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Carbidic Bainitic and Ausferritic Ductile Cast Iron

Archives of Metallurgy and Materials ◽

10.2478/amm-2013-0125 ◽

2013 ◽

Vol 58 (4) ◽

pp. 1053-1058 ◽

Cited By ~ 5

Author(s):

G. Gumienny

Keyword(s):

Cast Iron ◽

Solid State ◽

Thermal Effects ◽

Metal Matrix ◽

Lower Bainite ◽

Ductile Cast Iron ◽

Iron Metal ◽

Derivative Analysis ◽

Upper Bainite ◽

Matrix Components

Abstract This article presents new kinds of carbidic ductile cast iron with different microstructures of the metal matrix. This cast iron was obtained using the Inmold method nodularisation which guarantees strong refining of graphite and the metal matrix components. A different microstructure of the metal matrix of the cast iron was obtained without any thermal treatment (unwrought) by a suitable composition of alloy additives. It was shown that by adding molybdenum, chromium, nickel and copper it is possible to obtain in the cast iron metal matrix consisting of upper bainite, its mixture with lower bainite or ausferrite in the casts with the wall thickness of 3/25 mm. The process of cast iron crystallization is presented and described with the help of the thermal and derivative analysis (TDA) curves. It also shows the thermal effects from transformation of austenite in solid state.

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Microstructure and Properties of Cast Iron with Semi-Solid Process Using Cooling Plate Technique

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.457.79 ◽

2010 ◽

Vol 457 ◽

pp. 79-83 ◽

Cited By ~ 2

Author(s):

Mitsuharu Takita

Keyword(s):

Tensile Strength ◽

Cast Iron ◽

Gray Iron ◽

Ductile Cast Iron ◽

Advanced Materials ◽

Damping Capacity ◽

Cooling Plate ◽

Plate Technique ◽

Wide Range ◽

Semi Solid

Semi-solid metal processing with the cooling plate technique is one of the key technologies for producing advanced materials. The multitude of cast iron families with their wide range of mechanical properties, and relatively low costs combined with the advantage of semi-solid processing allow production of high quality cast components from cast iron. The effect of semi-solid processing using the cooling plate technique on the microstructure and the properties of cast iron is studied. The investigated material is hypo-eutectic, hyper-eutectic gray iron, compacted graphite and ductile cast iron. The results indicated that the microstructure (primary austenite and graphite) becomes finer and more globular by increasing the fraction of solid. The tensile strength of semi-solid processed cast iron is relatively high compared with ordinary cast iron. The values of both the tensile strength and the elongation depend on the fraction of solid. The total fracture strength is observed to depend on the graphite morphology as well as the matrix contribution that mainly depends on fraction of solid. The wear resistance and damping capacity of cast iron were investigated as a function of the relative amount of primary fraction of solid.

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