Structural Evolution and Deformation Behavior of Extruded AZ91 with Ca Addition in the Semi-Solid State

2006 ◽  
Vol 116-117 ◽  
pp. 775-778
Author(s):  
S.M. Liang ◽  
Rong Shi Chen ◽  
Jean Jacques Blandin ◽  
Michel Suéry ◽  
En Hou Han
Keyword(s):  
Solid State ◽  
Microstructural Evolution ◽  
Mechanical Response ◽  
Liquid Fraction ◽  
Structural Evolution ◽  
Solid Particles ◽  
Az91 Alloy ◽  
Compression Behavior ◽  
Ca Addition ◽  
Semi Solid

The microstructural evolution and mechanical response in compression in the semi-solid state of previously extruded AZ91 alloys containing two levels of Ca additions (1mass%Ca (AZC911) and 2mass%Ca (AZC912)) have been studied. Ca additions have a significant effect on microstructural evolution and compression behavior of the AZ91 alloy. At 515°C, the liquid fraction in AZC911 is larger than that in AZC912, so that the compression stress of the AZC912 alloy was found to be much larger than that of the AZC911 alloy. This behavior is explained through DSC analysis which suggests that some solid Al2Ca phase remains in AZC912 alloy at this temperature. Increasing the remelting temperature for this alloy leads to more liquid and coarsening of the solid particles occurs with increasing holding time.

Effect of Recrystallization and Partial Melting Method on Microstructural Evolution of SKD61 Tool Steel in Semi-Solid State

2012 ◽  
Vol 192-193 ◽  
pp. 209-214 ◽  
Author(s):  
Meng Yi ◽  
Sumio Sugiyama ◽  
Jun Yanagimoto
Keyword(s):  
Solid State ◽  
Partial Melting ◽  
Grain Refinement ◽  
Tool Steel ◽  
Microstructural Evolution ◽  
Solid Particles ◽  
Melting Method ◽  
Refinement Mechanism ◽  
Semi Solid ◽  
Lower Temperature

The microstructural evolution and basic refinement mechanism of the semi-solid-state SKD61 tool steel fabricated by recrystallization and partial melting (RAP) method were investigated experimentally. The effects of different parameters in RAP processing were systematically clarified to achieve the grain refinement of cast SKD61 steel in the semi-solid state. Results showed that, the microstructure of RAP processed specimen were finer and more globular than the microstructure of starting material. The distribution of finer solid particles in the RAP processed specimen was affected by the distribution of strain during predeformation. Uniform and spherical solid particles inclined to locate in the regions suffered from larger strain. The specimens subjected to a plastic predeformation at a lower temperature have a more uniform and spherical semi-solid microstructure than those specimens undergoing predeformation with the same reduction at higher temperatures. In addition, the grain refinement mechanism of SKD61 tool steel processed by RAP method was discussed.

Microstructural evolution of an ECAE-formed ZK60-RE magnesium alloy in the semi-solid state

2009 ◽  
Vol 506 (1-2) ◽  
pp. 8-15 ◽  
Author(s):  
Zude Zhao ◽  
Qiang Chen ◽  
Yanbin Wang ◽  
Dayu Shu
Keyword(s):  
Solid State ◽  
Magnesium Alloy ◽  
Microstructural Evolution ◽  
Semi Solid

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.

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

2008 ◽  
Vol 141-143 ◽  
pp. 695-700 ◽  
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.

Inductive Reheating of Steel Billets into the Semi-Solid State Based on Pyrometer Measurements

2006 ◽  
Vol 116-117 ◽  
pp. 734-737 ◽  
Author(s):  
Alexander Schönbohm ◽  
Rainer Gasper ◽  
Dirk Abel
Keyword(s):  
Solid State ◽  
Measurement Errors ◽  
Liquid Fraction ◽  
Solidus Temperature ◽  
Measurement Data ◽  
Heating Process ◽  
Production Environment ◽  
Loop Control ◽  
Control Scheme ◽  
Semi Solid

The aim of the paper is to demonstrate a control scheme by which it is possible to reproducibly reheat steel billets into the semi-solid state. Usually a heating program is used to reheat the billet into the semi-solid state. Our experiments showed that this control scheme leads to varying semi-solid fractions from one experiment to the next. To gain information about the billet’s state its temperature is often used since there is a known relationship between the temperature and the liquid fraction. Direct measurement of the temperature via thermocouples is not feasible in a production environment, therefore a radiation pyrometer has been used as a contact-less measurement device. The accuracy of the pyrometer depends heavily on the exact knowledge of the radiation coefficient, which can vary from billet to billet due to different surface properties and which is subject to change during the heating process. These uncertainties prohibit the implementation of a closed-loop control scheme since the exact temperature cannot be measured with the required accuracy. In order to be independent of the measurement errors the proposed control scheme only relies on the slope of the temperature. By detecting the distinct change of slope which occurs when the solidus temperature is crossed, the beginning of the melting process can be determined. The energy fed to the billet from this point onward determines the resulting liquid fraction. By detecting the entry into the solidusliquidus interval and then feeding the same amount of energy to each billet, it is guaranteed that the billet reaches the desired liquid fraction even by uncertain absolute value of the temperature and by small variations of the alloy composition. For the experiments the steel alloy X210 has been used and measurement data demonstrate the feasibility of the proposed control scheme.

scholarly journals Application of X-Ray Microtomography to Quantify the Liquid Fraction of M2 Steel for Semi-Solid Forming Process

2013 ◽  
Vol 554-557 ◽  
pp. 547-552 ◽  
Author(s):  
Guo Chao Gu ◽  
Raphaël Pesci ◽  
Eric Becker ◽  
Laurent Langlois ◽  
Régis Bigot
Keyword(s):  
Mechanical Properties ◽  
Solid State ◽  
Liquid Fraction ◽  
High Energy ◽  
Material Behavior ◽  
Model Alloy ◽  
Processing Temperature ◽  
Volume Percentage ◽  
X Ray ◽  
Semi Solid

Thixoforging, one variant of semi-solid metal processing in which the metallic alloys are processed at low liquid fraction (0.1< Fl < 0.3), is used to produce complex parts with high mechanical properties. Steel thixoforging faces more challenges as compared to that of low melting point materials due to high processing temperature and lack of understanding of the thermomechanical behavior of materials in the given conditions. It is crucial to study the microstructure at the semi-solid state to improve the understanding of the thixoforging process since the material behavior strongly depends on main parameters: the liquid fraction, its distribution as well as the coherence of the solid skeleton. The microstructure has a great influence on the viscosity of the material, on the flows and finally on the final shape and mechanical properties of the thixoforged parts. Here, the characterization of the volume percentage and distribution of liquid fraction at the semi-solid state with high energy 3D X-ray microtomography was investigated on M2 steel grade as a ‘model’ alloy. The obtained results have been compared to 2D observations using EDS technique in SEM on heated and quenched specimens. They showed a good correlation making both approaches very efficient for the study of the liquid zones at the semi-solid state.

scholarly journals The microstructural evolution and hardness of the equiatomic CoCrCuFeNi high-entropy alloy in the semi-solid state

2018 ◽  
Vol 745 ◽  
pp. 75-83 ◽  
Author(s):  
L.J. Zhang ◽  
J.T. Fan ◽  
D.J. Liu ◽  
M.D. Zhang ◽  
P.F. Yu ◽  
...  
Keyword(s):  
Solid State ◽  
Microstructural Evolution ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Semi Solid

Microstructure Evolution of Mg-6Zn-6Al Magnesium Alloy during Semi-Solid Partial Remelting

2011 ◽  
Vol 306-307 ◽  
pp. 608-612
Author(s):  
Xiao Feng Huang ◽  
K. Feng ◽  
Y. Ma ◽  
F.Y Yan ◽  
Ti Jun Chen
Keyword(s):  
Solid State ◽  
Magnesium Alloy ◽  
Shape Factor ◽  
Solid Particles ◽  
Dendritic Microstructure ◽  
Partial Remelting ◽  
Semi Solid ◽  
Average Size ◽  
Microstructure Of The Material ◽  
Holding Temperature

A new magnesium alloy, named as Mg-6Zn-6Al(ZA66), using for thixoforming production has been developed. The microstructure of the material during partial remelting holding in the semi-solid state was characterized. The results indicate that non-dendrite microstructure in ZA66 magnesium alloy billets can be obtained, but the proper partial remelting temperature and holding time should be select. After being treated at 575°Cfor 20 min, the ZA66 alloys can obtain a non-dendritic microstructure with finer unmelted primary solid particles (37 μm) and shape factor about 0.6. With the increasing holding temperature from 575°C to 590°C,the average size of unmelted primary solid particles increases and globular tendency becomes more obvious.

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