High ductility of magnesium at different strain rates under pressure

2019 ◽  
pp. 27-34
Author(s):  
R. V. Churbaev ◽  
V. P. Fedotov ◽  
E. R. Cheremitsyna
Keyword(s):  
Hydrostatic Pressure ◽  
Strain Rate ◽  
Large Deformation ◽  
Room Temperature ◽  
Pure Magnesium ◽  
High Plasticity ◽  
Strain Rates ◽  
High Ductility ◽  
Brittle Transition ◽  
Deformation Speed

The influence of the strain rate in the range of 3.3·10-5to 332 sec-1on the ductility of pure magnesium under hydrostatic pressure varying since 0.1 to 800 MPa and room temperature (293 K) has been researched. High plasticity of magnesium with small and large deformation speed under pressure was found. At pressure pure magnesium ductility reduces while strain rate increases; reduced plasticity is observed only when strain rate is equal to 0.17 sec-1, and above this rate, on the contrary, the ductility of magnesium increases. It is shown that the pressure at ductile-brittle transition increases from 142.2 to 241.5 MPa with strain rate increasing from 3.3·10-4up to 332 sec-1.

The effect of strain rates on tensile deformation of ultrafine-grained copper

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744014
Author(s):  
M. Li ◽  
Q. W. Jiang
Keyword(s):  
Strain Rate ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Tensile Deformation ◽  
Strain Rates ◽  
Roll Bonding ◽  
Fracture Elongation ◽  
Tensile Deformation Behavior ◽  
Ultrafine Grained ◽  
Flow Stress Level

Tensile deformation behavior of ultrafine-grained (UFG) copper processed by accumulative roll-bonding (ARB) was studied under different strain rates at room temperature. It was found that the UFG copper under the strain rate of 10[Formula: see text] s[Formula: see text] led to a higher strength (higher flow stress level), flow stability (higher stress hardening rate) and fracture elongation. In the fracture surface of the sample appeared a large number of cleavage steps under the strain rate of 10[Formula: see text] s[Formula: see text], indicating a typical brittle fracture mode. When the strain rate is 10[Formula: see text] or 10[Formula: see text] s[Formula: see text], a great amount of dimples with few cleavage steps were observed, showing a transition from brittle to plastic deformation with increasing strain rate.

Local Investigations of the Mechanical Properties of Ultrafine Grained Metals by Nanoindentations

2006 ◽  
Vol 503-504 ◽  
pp. 31-36 ◽  
Author(s):  
Johannes Mueller ◽  
Karsten Durst ◽  
Dorothea Amberger ◽  
Matthias Göken
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Fcc Metals ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Indentation Strain

The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.

scholarly journals Influence of strain rate and heat treatments on tensile and creep properties of Zn-0.15Cu-0.07Ti alloys

DYNA ◽  
2016 ◽  
Vol 83 (195) ◽  
pp. 77-83 ◽  
Author(s):  
María José Quintana Hernández ◽  
José Ovidio García ◽  
Roberto González Ojeda ◽  
José Ignacio Verdeja
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Strain Rates ◽  
Creep Tests ◽  
Design Problems ◽  
Creep Properties ◽  
Heat Treated ◽  
Zn Alloys

The use of Cu and Ti in Zn alloys improves mechanical properties as solid solution and dispersoid particles (grain refiners) may harden the material and reduce creep deformation. This is one of the main design problems for parts made with Zn alloys, even at room temperature. In this work the mechanical behavior of a Zn-Cu-Ti low alloy is presented using tensile tests at different strain rates, as well as creep tests at different loads to obtain the value of the strain rate coefficient m in samples parallel and perpendicular to the rolling direction of the Zn strip. The microstructure of the alloy in its raw state, as well as heat treated at 250°C, is also analyzed, as the banded structure produced by rolling influences the strengthening mechanisms that can be achieved through the treatment parameters.

Strain rate sensitivity of a mild steel at room temperature and strain rates of up to 105s−1

1980 ◽  
Vol 15 (4) ◽  
pp. 201-207 ◽  
Author(s):  
M S J Hashmi
Keyword(s):  
Finite Difference ◽  
Mild Steel ◽  
Strain Rate ◽  
Strain Hardening ◽  
Strain Rate Sensitivity ◽  
Elastic Strain ◽  
Room Temperature ◽  
Numerical Technique ◽  
Rate Sensitivity ◽  
Strain Rates

Experimental results on a mild steel are reported from ballistics tests which gave rise to strain rates of up to 105 s−1. A finite-difference numerical technique which incorporates material inertia, elastic-strain hardening and strain-rate sensitivity is used to establish the strain-rate sensitivity constants p and D in the equation, σ4 = σ1 (1+(∊/D)1/ p). The rate sensitivity established in this study is compared with those reported by other researchers.

scholarly journals Factors Influencing the Plane-Strain Crack Toughness Values of a Structural Steel

1969 ◽  
Vol 91 (3) ◽  
pp. 506-511 ◽  
Author(s):  
A. K. Shoemaker
Keyword(s):  
Strain Rate ◽  
Structural Steel ◽  
Yield Stress ◽  
Plane Strain ◽  
Stress Level ◽  
Room Temperature ◽  
Fatigue Cracking ◽  
Strain Rates ◽  
Fatigue Stress ◽  
Plane Strain Crack

An investigation was conducted to determine the effects of the variables; temperature, strain rate, and precracking fatigue-stress level, on plane-strain crack toughness values of a rate and temperature-sensitive steel. The crack toughness behavior of a 3/4-in-thick structural steel plate, which had a static room-temperature yield stress of 45,000 psi, was examined over the temperature range from −280 to 0 deg F for strain rates of 8 × 10−5/sec, 3 × 103/sec, and 1.5/sec. Crack toughness data, which were obtained from notched bend and single-edge-notched specimens, are presented for precracking conditions obtained at a maximum nominal fatigue stress of 25 percent and 50 percent of the room-temperature yield stress. The plane-strain crack toughness, KIc-values showed only a small sensitivity to changes in temperature and no effect due to changes in strain rate. The beginning of the transition from plane-strain to plane-stress conditions occurred at successive increases in temperature for increasing strain rate. The requirement of B > 2.5 × (KIc/σys)2 for plane-strain behavior of high-strength steels was also valid for this material when the yield stress was evaluated at the test temperature and strain rate. Increasing the fatigue-cracking stress level from 25 to 50 percent of the room-temperature nominal yield stress increased the apparent KIc-values. The data showed that a necessary condition for obtaining valid KIc-values is that the plastic-zone size which develops during fatigue cracking at room temperature must be less than that which occurs at the low temperatures and elevated strain rates of the KIc tests.

Effects of Strain Rate on Mechanical Properties and Microstructure of V-5Cr-5Ti Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 2535-2538
Author(s):  
Wen Jun Hu ◽  
Xi Cheng Huang ◽  
Fang Ju Zhang ◽  
Jun Mei ◽  
Yi Xia Yan ◽  
...  
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
High Strain ◽  
Lath Martensite ◽  
Optical Microscope ◽  
Tensile Fracture ◽  
Strain Rates ◽  
Brittle Ductile Transition ◽  
Transition Strain ◽  
Brittle Mode

In this work the static and dynamic tensile properties of vanadium alloy V-5Cr-5Ti were investigated at strain rates ranged from 3.3x10-5/s to 1.2x102/s. The material microstructures were analyzed using optical microscope, SEM, TEM, XRD and EDS. Results show that the yield strength a increases with strain rate. The brittle-ductile transition strain-rate is about 101/s to102/s. At room temperature the tensile fracture at a low strain rate occurs via mixed modes of microvoid aggregating and transgranular cracking; at high strain rate the fracture occurs via a brittle mode. The analysis by TEM, XRD and EDX shows the existence of lath martensite, and on there exits precipitate phase of Ti(O,C, N) in grain boundaries.

Effect of Temperature and Strain Rate on the Mechanical Properties of 99.5 Aluminium Rods Extruded by KOBO

2016 ◽  
Vol 879 ◽  
pp. 230-235
Author(s):  
Sonia Boczkal ◽  
Marzena Lech-Grega ◽  
Wojciech Szymanski ◽  
Paweł Ostachowski ◽  
Marek Lagoda
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
High Strain ◽  
Effect Of Temperature ◽  
Recrystallization Process ◽  
Extrusion Force ◽  
Strain Rates ◽  
High Strain Rates ◽  
Constant Frequency ◽  
Increasing Temperature

In this study, aluminium rods were cold extruded in a direct process by KOBO method in two variants: variant I with varying (decreasing) frequency of die oscillations necessary to maintain a constant extrusion force, and variant II with constant frequency of die oscillations, leading to a decrease in the extrusion force. The tensile test of rods was carried out in a temperature range of 20 - 200°C and at a strain rate from 8xE10-5 to 8xE10-1 s-1. Significant differences in the elongation of the tested rods were observed. It was found that rods extruded at variable die oscillations and stretched at room temperature had similar elongation, independent of the strain rate. With the increase of temperature, the elongation of samples stretched at a low speed was growing from a value of about 8% at room temperature up to 40% at 200°C. At high strain rates, despite the increasing temperature, the elongation remained at the same level, i.e. 5-6%. In rods extruded at constant die oscillations, the elongation at a low strain rate was growing with the temperature from 10% at room temperature up to 29% at 200°C. At high strain rates, the elongation decreased from 28% at room temperature to 11% at 200°C. The results were interrelated with examinations of the structure of rods and fractures of tensile specimens. In the material extruded by KOBO method with constant die oscillations, the beginnings of the recrystallization process were observed, absent in the material extruded at variable die oscillations.

The Effect of Strain Rate on the Tensile Behavior of Electrodeposited Nanocrystalline Ni-Co Alloy

2012 ◽  
Vol 535-537 ◽  
pp. 353-356
Author(s):  
Li Yuan Qin ◽  
Jian She Lian ◽  
Long Zhe Quan ◽  
En Chen Jiang
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
Mechanical Performance ◽  
Rate Sensitivity ◽  
High Strength ◽  
Solid Solution Hardening ◽  
Strain Rates ◽  
Mechanism Transition ◽  
Surface Morphologies ◽  
High Strain Rate Sensitivity

A fully dense nanocrystalline Ni-Co alloy with 18 nm grain size exhibited high strength of about 2200 MPa and ductility of 8.19.2% at strain rates of 1.04×10-5 to 1.04 s-1 and room temperature. The alloying of Co element induces the grain refinement, solid solution hardening and decrease of stacking fault energy should contribute to the favorable combination of mechanical performance. The obvious distinctions of fracture-surface morphologies with strain rate alteration were attributed to underlying deformation mechanism transition. The high strain rate sensitivity exponent and small activation volume indicate that grain boundary activity may be expected in this alloy.

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.

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