Rate and Temperature Effect in Nanoindentation Testing on Hardness in SLM IN718

2021 ◽  
pp. 1-41
Author(s):  
Reem Abo Znemah ◽  
George Z. Voyiadjis ◽  
Paul Wood ◽  
Edris Akbari
Keyword(s):  
Cell Wall ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Mechanical Hardness ◽  
Effect Model ◽  
Heat Treated ◽  
Three Samples ◽  
Sensitivity Changes ◽  
Material Length Scale ◽  
Material Length

Abstract The microstructure and mechanical hardness of Inconel 718 (INC718) hexagonal honeycomb cellular structure manufactured by Selective Laser Melting (SLM) was studied in this work. Non-heat-treated SLM-produced samples with cell wall thicknesses of 0.4, 0.6 and 0.8 mm were studied. The hardness was measured using MTS Nanoindenter. For room temperature, continuous hardness measurements over penetration depths up to 2 µm under three different strain rates of 0.02, 0.05 and 0.08 s−1 was performed. For the 100 and 200°C, single hardness measurements at eight different depths were performed. The grain size was found to change considerably as the cell wall thickness changed from 0.6 mm to 0.4 mm compared to the change from 0.8 mm to 0.6 mm. similar trend in mechanical hardness reduction and strain rate sensitivity changes were observed between the three samples. The microstructure and hardness showed anisotropy between the planes parallel and perpendicular to the build planes as well. Temperature and strain rate indentation size effect model developed by the second author was modified and used to evaluate the intrinsic material length scale used in gradient plasticity theory.

scholarly journals Effect of Cell Wall Ductility and Toughness on Compressive Response and Strain Rate Sensitivity of Aluminium Foam

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Alexandra Byakova ◽  
Svyatoslav Gnyloskurenko ◽  
Andrey Vlasov ◽  
Nikolay Semenov ◽  
Yan Yevych ◽  
...  
Keyword(s):  
Cell Wall ◽  
Strain Rate ◽  
Dynamic Loading ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Melt Processing ◽  
Wall Material ◽  
Static Compression ◽  
Quasi Static Compression ◽  
Al Foams

The study presents the effect of cell wall ductility and toughness on the compressive behaviour of closed-cell Al foams under static and dynamic loading and localised deformation by indentation. Two kinds of Al alloys including relatively ductile AlSiMg alloy and high-strength AlZnMg alloy, which comprises a great amount of brittle eutectic domains, were used as matrix materials. Both kinds of Al foams were fabricated via newly developed melt processing using the CaCO3-foaming agent without Ca additive. Mechanical behaviour of Al foams under quasi-static compression and indentation was examined and compared with that performed under dynamic loading using direct impact tests. Characteristic events revealed in deformation patterns of Al foams at quasi-static compression were also monitored with the CCD camera. Significant differences in stress-strain response and strain rate sensitivity of Al foams arose from the difference in the microstructure, and hence, ductility and toughness of the cell wall material were investigated and discussed.

Superplasticity of an AZ91 Magnesium Alloy

2007 ◽  
Vol 567-568 ◽  
pp. 365-368 ◽  
Author(s):  
Zoltán Száraz ◽  
Zuzanka Trojanová ◽  
Talant Ryspaev ◽  
Volker Wesling
Keyword(s):  
Magnesium Alloy ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Hot Extrusion ◽  
Az91 Magnesium Alloy ◽  
Physical Mechanisms ◽  
Heat Treated ◽  
Elongation To Failure ◽  
Az91 Magnesium ◽  
Two Stages

The superplastic deformation characteristics of the AZ91, the mostly used magnesium alloy, were investigated at various strain rates in the interval from 3x10-5 to 1x10-2 s-1 and temperature of 420 °C. To prepare superplastic alloys thermo-mechanical treatment was used. Cast materials were heat-treated in two stages, after homogenization at 415 °C for 10 h were submitted to the precipitation annealing at temperature in the range of 200-380 °C for 10 h, and deformed by hot extrusion. Microstructure of samples was observed by the light microscope Olympus. Strain rate sensitivity parameter m has been estimated by the abrupt strain rate changes method. The strong strain rate dependence of the m-parameter was found. The highest elongation to failure, 584%, was found for the samples aged at 380 °C. Possible physical mechanisms of the superplastic flow are discussed.

Behavio of Supeaplastically Extruded Cu-26wt%Zn–3.5wt%Al Shape Memory Alloy

1990 ◽  
Vol 196 ◽  
Author(s):  
Zheng Zhengyt ◽  
Zhcng Weijian ◽  
Lin Fuzeng ◽  
Chew Yingsheng
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Strain Rate ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Heat Treated

ABSTRACTThe influence of superplastic extrusion on the microstructures and the shape memory effect of the Cu-Zn-Al shape memory alloys has been investigated. The shape memory alloy Cu-26%wt%Zn-3.5wt%Al is superplastio with an index of strain rate sensitivity n = 0.48 at 600°C, at a strain of . After extrusion under the superplastio condition the miorostruotures are improved and no cavities are observed. The superplastically extruded specimens of this alloy were heat-treated to obtain the shape memory effect. These specimens indicate that no deterioration of shape memory effect of the alloy is induced by the superplastio extrusion and the shape memory effect of the alloy is somewhat improved.

Analysis of Cavitation in a Near-γ Titanium Aluminide During High-Temperature/Superplastic Deformation

1999 ◽  
Vol 601 ◽  
Author(s):  
Carl M. Lombard ◽  
Amit K. Ghosh ◽  
S. Lee Semiatin
Keyword(s):  
Strain Rate ◽  
Growth Rates ◽  
Titanium Aluminide ◽  
Flow Behavior ◽  
Cavity Growth ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Initial Structure ◽  
Heat Treated ◽  
Actual Growth

AbstractThe superplastic flow behavior of a near-γ titanium aluminide (Ti-45.5Al-2Cr-2Nb) is determined under uniaxial tension in as-rolled or rolled-and-heat treated conditions (1177°C/4 hr or 1238°C/2 hr). Cavitation characteristics, including cavity growth rates, are established via isothermal, constant strain rate tests conducted at 10−4 to 10−2 s−1 and temperatures between 900°C and 1200°C. Differences in cavitation as a function of initial structure, strain, strain rate and temperature are noted. Cavity growth is found to be largely plasticity controlled. Experimental growth rates are compared with equations that predict rates as a function of strain rate sensitivity. Although the equations assume no coalescence and no nucleation of new cavities, which are experimentally observed, they are useful in predicting actual growth rates.

The effects of strain and strain rate on residual microstructures in copper

1986 ◽  
Vol 44 ◽  
pp. 420-421
Author(s):  
M. F. Stevens ◽  
P. S. Follansbee
Keyword(s):  
Strain Rate ◽  
Applied Stress ◽  
Threshold Stress ◽  
Rate Sensitivity ◽  
Viscous Drag ◽  
Strain Rates ◽  
Strain And Strain Rate ◽  
Threshold Strength ◽  
Mechanism Transition ◽  
Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

On size-dependent bending behaviors of shape memory alloy microbeams via nonlocal strain gradient theory

2021 ◽  
pp. 1045389X2098699
Author(s):  
Bo Zhou ◽  
Zetian Kang ◽  
Xiao Ma ◽  
Shifeng Xue
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Functionally Graded ◽  
Strain Gradient Theory ◽  
Gradient Theory ◽  
Size Dependent ◽  
Material Length Scale Parameter ◽  
Material Length Scale ◽  
Material Length ◽  
Nonlocal Strain Gradient

This paper focuses on the size-dependent behaviors of functionally graded shape memory alloy (FG-SMA) microbeams based on the Bernoulli-Euler beam theory. It is taken into consideration that material properties, such as austenitic elastic modulus, martensitic elastic modulus and critical transformation stresses vary continuously along the longitudinal direction. According to the simplified linear shape memory alloy (SMA) constitutive equations and nonlocal strain gradient theory, the mechanical model was established via the principle of virtual work. Employing the Galerkin method, the governing differential equations were numerically solved. The functionally graded effect, nonlocal effect and size effect of the mechanical behaviors of the FG-SMA microbeam were numerically simulated and discussed. Results indicate that the mechanical behaviors of FG-SMA microbeams are distinctly size-dependent only when the ratio of material length scale parameter to the microbeam height is small enough. Both the increments of material nonlocal parameter and ratio of material length-scale parameter to the microbeam height all make the FG-SMA microbeam become softer. However, the stiffness increases with the increment of FG parameter. The FG parameter plays an important role in controlling the transverse deformation of the FG-SMA microbeam. This work can provide a theoretical basis for the design and application of FG-SMA microstructures.

A Study on the Flow Behavior of 42CrMo Steel under Hot Compression by Thermal Physical Simulations

2010 ◽  
Vol 108-111 ◽  
pp. 494-499
Author(s):  
Ying Tong ◽  
Guo Zheng Quan ◽  
Gang Luo ◽  
Jie Zhou
Keyword(s):  
Strain Rate ◽  
Flow Behavior ◽  
Rate Sensitivity ◽  
Strain Hardening Exponent ◽  
Forming Process ◽  
Material Parameters ◽  
Basic Model ◽  
42Crmo Steel ◽  
Plastic Forming ◽  
Physical Simulations

This work was focused on the compressive deformation behavior of 42CrMo steel at temperatures from 1123K to 1348K and strain rates from 0.01s-1 to 10s-1 on a Gleeble-1500 thermo-simulation machine. The true stress-strain curves tested exhibit peak stresses at small strains, after them the flow stresses decrease monotonically until high strains, showing a dynamic flow softening. And the stress level decreases with increasing deformation temperature and decreasing strain rate. The values of strain hardening exponent n, and the strain rate sensitivity exponent m were calculated the method of multiple linear regression, the results show that the two material parameters are not constants, but changes with temperature and strain rate. Then the two variable material parameters were introduced into Fields-Backofen equation amended. Thus the constitutive mechanical discription of 42CrMo steel which can accurately describe the relationships among flow stress, temperature, strain rate, strain offers the basic model for plastic forming process simulation.

scholarly journals Negative Strain Rate Sensitivity Induced by Structure Heterogeneity in Zr64.13Cu15.75Ni10.12Al10 Bulk Metallic Glass

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 339
Author(s):  
Xiang Wang ◽  
Zhi Qiang Ren ◽  
Wei Xiong ◽  
Si Nan Liu ◽  
Ying Liu ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Strain Rate Sensitivity ◽  
Critical Role ◽  
Rate Sensitivity ◽  
Confined Compression ◽  
Negative Strain Rate Sensitivity ◽  
Cast Specimen ◽  
Structure Heterogeneity

The negative strain rate sensitivity (SRS) of metallic glasses is frequently observed. However, the physical essence involved is still not well understood. In the present work, small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM) reveal the strong structure heterogeneity at nanometer and tens of nanometer scales, respectively, in bulk metallic glass (BMG) Zr64.13Cu15.75Ni10.12Al10 subjected to fully confined compression processing. A transition of SRS of stress, from 0.012 in the as-cast specimen to −0.005 in compression processed specimen, was observed through nanoindentation. A qualitative formulation clarifies the critical role of internal stress induced by structural heterogeneity in this transition. It reveals the physical origin of this negative SRS frequently reported in structurally heterogeneous BMG alloys and its composites.

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