scholarly journals Statistical Analysis of Grain-Scale Effects of Twinning Deformation for Magnesium Alloys under Cyclic Strain Loading

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2454
Author(s):  
Damin Lu ◽  
Shuai Wang ◽  
Yongting Lan ◽  
Keshi Zhang ◽  
Wujun Li ◽  
...  
Keyword(s):  
Grain Size ◽  
Statistical Analysis ◽  
Magnesium Alloys ◽  
Probability Function ◽  
Volume Fraction ◽  
Scale Effects ◽  
Low Cycle Fatigue ◽  
Cyclic Strain ◽  
Statistical Distribution ◽  
Twin Thickness

To reveal the relationship between grain size and twinning deformation of magnesium alloys under cyclic strain, this study carried out a group of strain-controlled low-cycle fatigue experiments and statistical analysis of microstructures. Experimental results show that the shape of the hysteresis loop exhibits significant asymmetry at different strain amplitudes, and the accumulation of residual twins plays an important role in subsequent cyclic deformation. For the different strain amplitudes, the statistical distribution of the grain size of magnesium alloy approximately follows the Weibull probability function distribution, while the statistical distribution of twin thickness is closer to that of Gaussian probability function. The twin nucleation number (TNN) increases with the increase of grain size, but there is no obvious function relationship between twin thickness and grain size. Twin volume fraction (TVF) increases with the increase of grain size, which is mainly due to the increase of TNN. This work can provide experimental evidence for a more accurate description of the twinning deformation mechanism.

The Influence of Section Thickness on Microstructure of Elektron 21 and QE22 Magnesium Alloys

2012 ◽  
Vol 191 ◽  
pp. 145-150 ◽  
Author(s):  
Michał Stopyra ◽  
Robert Jarosz ◽  
Andrzej Kiełbus
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Magnesium Alloys ◽  
Statistical Methods ◽  
Wall Thickness ◽  
Light Microscope ◽  
Volume Fraction ◽  
Grain Structure ◽  
Section Thickness ◽  
Gating System

The paper presents analysis of section thickness’ influence on microstructure of Elektron 21 and QE22 magnesium alloys in the form of a stepped casting test. Solid solution grain size and volume fraction of eutectic areas were measured using light microscope and sterological methods. The results showed the significant increase of grain size caused by wall thickness and its slight decrease connected with the distance beetwen analysed section and the gating system. This relationship was confirmed using statistical methods. QE22 alloy demonstrated finer grain structure than Elektron 21 alloy as well as lesser susceptibility of grain size to solidification conditions

Research on the Microstructures and Mechanical Properties of Annealed Cold Upsetting AZ31 Magnesium Alloy

2009 ◽  
Vol 610-613 ◽  
pp. 826-830
Author(s):  
Tian Mo Liu ◽  
Wei Hui Hu ◽  
Qing Liu
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Annealing Temperature ◽  
Volume Fraction ◽  
Cold Upsetting ◽  
Cast Magnesium Alloys ◽  
Microstructures And Mechanical Properties ◽  
Cast Magnesium

The microstructures and mechanical properties of cold upsetting magnesium alloys were investigated upon anneal under different conditions. The results show that a large amount of twins were observed in the original grains of cold upsetting AZ31 magnesium alloys. The twins disappeared gradually and recrystal grains formed after anneal. The volume fraction of the recrystal grains increases as the strain of samples rises. Recrystal grain size grows large with the elevated annealing temperature. Recrystal grain size reduces at first and then grows as the annealing time is prolonged. In addition, compared with as-cast magnesium alloys, the yield strength of cold upsetting samples increase apparently due to grain refinement after anneals.

The Influence of Strontium on the Microstructure of Cast Magnesium Alloys Containing Aluminum and Calcium

2014 ◽  
Vol 607 ◽  
pp. 37-42
Author(s):  
Bartlomiej Dybowski ◽  
Tomasz Rzychoń ◽  
Bartosz Chmiela
Keyword(s):  
Solid Solution ◽  
Grain Size ◽  
Magnesium Alloys ◽  
Aluminum Content ◽  
Volume Fraction ◽  
Strontium Content ◽  
Cast Magnesium Alloys ◽  
Cast Magnesium

The influence of strontium addition on the microstructure of a Mg-9Al-2Ca alloy was investigated. The microstructure of Mg-9Al-2Ca-xSr alloys consists of α-Mg, (Mg,Al)2Ca with C15 structure, Al4Sr and AlxMny phases. The addition of strontium decreases the grain size of the α-Mg phase and decreases the aluminum content dissolved in the α-Mg solid solution. Moreover, the volume fraction of the Al4Sr phase increases with increasing strontium content. Strontium does not influence on the volume fraction of (Mg,Al)2Ca phase.

Influence of the Pouring Temperature on the Castability and Microstructure of Elektron 21 and QE22 Magnesium Casting Alloys

2013 ◽  
Vol 197 ◽  
pp. 125-130
Author(s):  
Bartłomiej Dybowski ◽  
Robert Jarosz ◽  
Andrzej Kiełbus
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Magnesium Alloys ◽  
Automotive Industry ◽  
Volume Fraction ◽  
Low Density ◽  
Pouring Temperature ◽  
Casting Alloys ◽  
Magnesium Casting

Magnesium alloys are widely used in aerospace and automotive industry due to their low density, good mechanical properties and good castability. The paper presents results of the castability tests and microstructural investigations on two unmodified magnesium casting alloys, Elektron 21 and QE22. Spirals for the castability test were poured from three temperatures: 755°C, 800°C and 835°C. Volume fraction of eutectic regions and grain size in both alloys were quantitatively evaluated. Castability increased with increasing pouring temperature. Quantity of eutectics and grain size did not show straight correlation with pouring temperature.

Strengthening and Improving Yield Asymmetry of Magnesium Alloys by Second Phase Particle Refinement Under the Guidance of Integrated Computational Materials Engineering

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Dongsheng Li ◽  
Curt Lavender
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Magnesium Alloys ◽  
Volume Fraction ◽  
Phase Particle ◽  
Fuel Efficiency ◽  
Co2 Production ◽  
Precipitate Size ◽  
Second Phase ◽  
Precipitate Volume Fraction

Improving yield strength and asymmetry is critical to expand applications of magnesium alloys in industry for higher fuel efficiency and lower CO2 production. Grain refinement is an efficient method for strengthening low symmetry magnesium alloys, achievable by precipitate refinement. This study provides guidance on how precipitate engineering will improve mechanical properties through grain refinement. Precipitate refinement for improving yield strengths and asymmetry is simulated quantitatively by coupling a stochastic second phase grain refinement model and a modified polycrystalline crystal viscoplasticity φ-model. Using the stochastic second phase grain refinement model, grain size is quantitatively determined from the precipitate size and volume fraction. Yield strengths, yield asymmetry, and deformation behavior are calculated from the modified φ-model. If the precipitate shape and size remain constant, grain size decreases with increasing precipitate volume fraction. If the precipitate volume fraction is kept constant, grain size decreases with decreasing precipitate size during precipitate refinement. Yield strengths increase and asymmetry approves to one with decreasing grain size, contributed by increasing precipitate volume fraction or decreasing precipitate size.

Microstructural Control of Ductile Crack Propagation in TMCP HSLA Pipeline Steels

2014 ◽  
Vol 922 ◽  
pp. 568-573
Author(s):  
Victor Carretero Olalla ◽  
N. Sanchez Mouriño ◽  
Philippe Thibaux ◽  
Leo Kestens ◽  
Roumen H. Petrov
Keyword(s):  
Grain Size ◽  
Crack Propagation ◽  
Volume Fraction ◽  
Main Role ◽  
Charpy Test ◽  
Initiation And Propagation ◽  
Average Grain Size ◽  
Main Disadvantage ◽  
Steel Grades ◽  
Increasing Demand

Control of ductile fracture propagation is one of the major concerns for pipeline industry, particularly with the increasing demand of new control rolled steel grades required to maintain integrity at high operational pressures. The objective of this research is to understand which microstructural features govern crack propagation, and to analyse the effect of two of them (average grain size, and volume fraction of pearlite). The main disadvantage during classical Charpy test was to discriminate the crack initiation and propagation energy during fracture of a notched sample. The initiation appears to be caused by the stress state in the neighbouring of Ti-containing precipitates or pearlite particles (no presence of M/A constituents or MnS inclusions was detected in the evaluated grades), propagation-arrest of the crack is assumed to play the main role concerning the control of fracture. Our approach to characterize the fracture resistance is to measure the energy absorbed during the crack propagation stage by means of load-displacement curves obtained via instrumented Charpy test. It was observed that the energy absorbed during crack propagation is not influenced by the average grain size but by the fraction and the morphological (banded-not banded) distribution of second pearlitic phase. This suggests that a different approach to characterize the heterogeneities in grain size clustering might be followed to correlate the energy measured during crack propagation and the morphological features of the steel.

Study on Dynamic Recrystallization Behavior in Deformed Austenite of 52100 Steel by Using JMAK-Model

2013 ◽  
Vol 275-277 ◽  
pp. 1833-1837
Author(s):  
Ke Lu Wang ◽  
Shi Qiang Lu ◽  
Xin Li ◽  
Xian Juan Dong
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Volume Fraction ◽  
True Strain ◽  
Strain And Strain Rate ◽  
Average Grain Size ◽  
Dynamic Recrystallization Behavior ◽  
Simulation And Experiment ◽  
Good Agreement

A Johnson-Mehl-Avrami-Kolmogorov (JMAK)-model was established for dynamic recrystallization in hot deformation process of 52100 steel. The effects of hot deformation temperature, true strain and strain rate on the microstructural evolution of the steel were physically studied by using Gleeble-1500 thermo-mechanical simulator and the experimental results were used for validation of the JMAK-model. Through simulation and experiment, it is found that the predicted results of DRX volume fraction, DRX grain size and average grain size are in good agreement with the experimental ones.

scholarly journals A Dislocation-Based Theory for the Deformation Hardening Behavior of DP Steels: Impact of Martensite Content and Ferrite Grain Size

2010 ◽  
Vol 2010 ◽  
pp. 1-16 ◽  
Author(s):  
Yngve Bergström ◽  
Ylva Granbom ◽  
Dirk Sterkenburg
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Deformation Process ◽  
Volume Fraction ◽  
High Energy ◽  
Martensite Content ◽  
Plastic Deformation Process ◽  
Deformation Hardening ◽  
Dp Steels ◽  
Ferrite Grain Size

A dislocation model, accurately describing the uniaxial plastic stress-strain behavior of dual phase (DP) steels, is proposed and the impact of martensite content and ferrite grain size in four commercially produced DP steels is analyzed. It is assumed that the plastic deformation process is localized to the ferrite. This is taken into account by introducing a nonhomogeneity parameter, f(ε), that specifies the volume fraction of ferrite taking active part in the plastic deformation process. It is found that the larger the martensite content the smaller the initial volume fraction of active ferrite which yields a higher initial deformation hardening rate. This explains the high energy absorbing capacity of DP steels with high volume fractions of martensite. Further, the effect of ferrite grain size strengthening in DP steels is important. The flow stress grain size sensitivity for DP steels is observed to be 7 times larger than that for single phase ferrite.

Sign in / Sign up

Export Citation Format

Share Document