scholarly journals Influence of Strain Rate, Temperature and Chemical Composition on High Silicon Ductile Iron

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 391
Author(s):  
Henrik Borgström
Keyword(s):  
Grain Boundary ◽  
Ductile Iron ◽  
High Strain ◽  
Deformation Mechanisms ◽  
Strain Rates ◽  
Silicon Iron ◽  
Cooling Conditions ◽  
Boundary Film ◽  
High Silicon ◽  
Boundary Films

Today, the use of solution hardened ductile iron is limited by brittleness under certain conditions. If chassis components are subjected to loads having high strain rates exceeding those imposed during tensile testing at sub-zero temperatures, unexpected failure can occur. Therefore, it is the purpose of this review to discuss three main mechanisms, which have been related to brittle failure in high silicon irons: intercritical embrittlement, the integrity of the ferritic matrix and deformation mechanisms in the graphite. Intercritical embrittlement is mainly attributed to the formation of Mg- and S-rich grain boundary films. The formation of these films is suppressed if the amount of free Mg- and MgS-rich inclusions is limited by avoiding excess Mg and/or by the passivation of free Mg with P. If the grain boundary film is not suppressed, the high silicon iron has very low elongations in the shakeout temperature regime: 300 to 500 °C. The integrity and strength of the ferrite are limited by the reduced ordering of the silicumferrite with increasing silicon content, once the “ordinary” ferrite is saturated at 3% silicon, depending on the cooling conditions. Finally, the graphite damaging mechanisms are what dictate the properties most at low temperatures (sub −20 °C).

Strain-Rate Sensitivity Enhanced by Grain-Boundary Sliding in Creep Condition for AZ31 Magnesium Alloy at Room Temperature

2016 ◽  
Vol 838-839 ◽  
pp. 106-109 ◽  
Author(s):  
Tetsuya Matsunaga ◽  
Hidetoshi Somekawa ◽  
Hiromichi Hongo ◽  
Masaaki Tabuchi
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
High Strain ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
High Strain Rates ◽  
Boundary Sliding

This study investigated strain-rate sensitivity (SRS) in an as-extruded AZ31 magnesium (Mg) alloy with grain size of about 10 mm. Although the alloy shows negligible SRS at strain rates of >10-5 s-1 at room temperature, the exponent increased by one order from 0.008 to 0.06 with decrease of the strain rate down to 10-8 s-1. The activation volume (V) was evaluated as approximately 100b3 at high strain rates and as about 15b3 at low strain rates (where b is the Burgers vector). In addition, deformation twin was observed only at high strain rates. Because the twin nucleates at the grain boundary, stress concentration is necessary to be accommodated by dislocation absorption into the grain boundary at low strain rates. Extrinsic grain boundary dislocations move and engender grain boundary sliding (GBS) with low thermal assistance. Therefore, GBS enhances and engenders SRS in AZ31 Mg alloy at room temperature.

Evolution of Texture and Microstructure of AZ31 Mg Alloy Sheet at High Strain Rates

2012 ◽  
Vol 706-709 ◽  
pp. 1255-1260 ◽  
Author(s):  
I. Ulacia ◽  
N.V. Dudamell ◽  
J.A. Esnaola ◽  
Sang Bong Yi ◽  
M.T. Perez-Prado ◽  
...  
Keyword(s):  
High Strain ◽  
Alloy Sheet ◽  
Deformation Mechanisms ◽  
Experimental Program ◽  
Strain Rates ◽  
Az31 Mg Alloy ◽  
Electron Backscatter ◽  
Tension And Compression ◽  
Critical Components ◽  
Rate Behaviour

The high strain rate behaviour of magnesium alloys is of great interest to automotive,aerospace and/or defence industries because some critical components should have the propermechanical properties to work under crash or impact conditions. In the current study, resultsfrom an extensive experimental program are presented. The uniaxial mechanical behaviour ofAZ31 sheet under dynamic conditions (ε=103 s-1) is analyzed and compared with that observedat low strain rates. AZ31 sheets have been tested in tension and compression using Hopkinsonbar apparatus at 25°C and 250°C. Moreover, interrupted tests were also performed in orderto relate the evolution of deformation mechanisms with strain. Finally, detailed microstructureand texture examination by electron backscatter di raction (EBSD) and neutron di ractionhas been carried out in order to elucidate the predominant deformation and recrystallizationmechanisms.

Experimental characterization and modeling of UO 2 grain boundary cracking at high temperatures and high strain rates

2015 ◽  
Vol 460 ◽  
pp. 184-199 ◽  
Author(s):  
Maxime Salvo ◽  
Jérôme Sercombe ◽  
Thomas Helfer ◽  
Philippe Sornay ◽  
Thierry Désoyer
Keyword(s):  
Grain Boundary ◽  
High Temperatures ◽  
High Strain ◽  
Strain Rates ◽  
Experimental Characterization ◽  
High Strain Rates

Simulation study of the effect of strain rate on the mechanical properties and tensile deformation of gold nanowire

2017 ◽  
Vol 31 (27) ◽  
pp. 1750247 ◽  
Author(s):  
Guo-Jie Shi ◽  
Jin-Guo Wang ◽  
Zhao-Yang Hou ◽  
Zhen Wang ◽  
Rang-Su Liu
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
High Strain ◽  
Strain Curve ◽  
Deformation Mechanisms ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Au Nanowire ◽  
Plastic Process

The mechanical properties and deformation mechanisms of Au nanowire during the tensile processes at different strain rates are revealed by the molecular dynamics method. It is found that the Au nanowire displays three distinct types of mechanical behaviors when tensioning at low, medium and high strain rates, respectively. At the low strain rate, the stress–strain curve displays a periodic zigzag increase–decrease feature, and the plastic deformation is resulted from the slide of dislocation. The dislocations nucleate, propagate, and finally annihilate in every decreasing stages of stress, and the nanowire always can recover to FCC-ordered structure. At the medium strain rate, the stress–strain curve gently decreases during the plastic process, and the deformation is contributed from sliding and twinning. The dislocations formed in the yield stage do not fully propagate and further escape from the nanowire. At the high strain rate, the stress-strain curve wave-like oscillates during the plastic process, and the deformation is resulted from amorphization. The FCC atoms quickly transform into disordered amorphous structure in the yield stage. The relative magnitude between the loading velocity of strain and the propagation velocity of phonons determines the different deformation mechanisms. The mechanical behavior of Au nanowire is similar to Ni, Cu and Pt nanowires, but their deformation mechanisms are not completely identical with each other.

High Strain Rate Compression Testing of Hot-Pressed TRIP/TWIP-Matrix-Composites

2017 ◽  
Vol 742 ◽  
pp. 113-120 ◽  
Author(s):  
Ralf Eckner ◽  
Lutz Krüger
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Deformation Mechanisms ◽  
Strain Rates ◽  
Strengthening Effect ◽  
Matrix Composites ◽  
High Strain Rates ◽  
The Matrix

Metal matrix composites with ceramic reinforcements such as particles or fibers have come into focus during the past decades due to rising requirements on engineering materials. In this work, composite materials out of high-alloy CrMnNi-steel matrices with varying Ni-contents (3 wt.% and 9 wt.%) and 10 vol.% Mg-PSZ were processed by hot-pressing. The variation in Ni-content resulted in a change in stacking fault energy (SFE) which significantly influenced the deformation mechanisms. The mechanical behavior of the developed composites was investigated in a wide strain rate range between 0.0004 s-1 and 2300 s-1 under compressive loading. This was done by a servohydraulic testing system, a drop weight tower, and a Split-Hopkinson Pressure Bar for the high strain rates. To study the influence on the deformation mechanisms such as martensitic transformations and/or twinning, interrupted tests were also carried out at 25 % compressive strain. Subsequent microstructural examinations were done by a magnetic balance to measure the quantity of α’-martensite as well as by scanning electron microscopy (SEM). The results show an increase of strength and strain hardening with decreasing SFE of the matrix due to increased α’-martensite formation. The addition of the Mg-PSZ particles resulted in further strengthening over almost the entire deformation range for all investigated composites. At high strain rates quasi-adiabatic heating suppressed the martensite transformation and reduced the strain hardening capacity of the matrix. Nonetheless the particle reinforcement retains its strengthening effect.

scholarly journals A Comparative Study on the Substructure Evolution and Mechanical Properties of TIMETAL® 407 and Ti-64

2020 ◽  
Vol 321 ◽  
pp. 11045
Author(s):  
Zachary Kloenne ◽  
Gopal Viswanathan ◽  
Matt Thomas ◽  
M.H. Lorreto ◽  
Hamish L. Fraser
Keyword(s):  
Titanium Alloys ◽  
High Strain ◽  
Weight Ratio ◽  
High Strength ◽  
Deformation Mechanisms ◽  
Strain Rates ◽  
Aerospace Applications ◽  
Beta Titanium ◽  
Excellent Candidate ◽  
Split Hopkinson

Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio. Alpha/beta titanium alloys are used in nearly all sections of the aircraft, including the fuselage, landing gear, and wing. Ti-6Al-4V is the workhorse alloy of the titanium industry, comprising of nearly 60% of total titanium production. TIMETAL® 407, Ti-0.85Al-3.9V-0.25Si-0.25Fe (Ti-407) is an excellent candidate for alloy applications requiring excellent machinability and increased energy absorption. These properties are a result of the alloy’s increased ductility while maintaining moderate levels of strength. In this study, the deformation mechanisms of Ti-407 have been studied at high strain rates using split-Hopkinson bar testing. Utilizing post-mortem characterization, Ti-407 has been shown to deform significantly by ⟨c+a⟩ slip and deformation twinning. The observation of ⟨c+a⟩ slip is in contrast with other studies and will be discussed further.

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