scholarly journals Comparison of Nano-Mechanical Behavior between Selective Laser Melted SKD61 and H13 Tool Steels

2018 ◽  
Author(s):  
Jaecheol Yun ◽  
Van Luong Nguyen ◽  
Jungho Choe ◽  
Dong-yeol Yang ◽  
Hak-sung Lee ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Tool Steels ◽  
Pile Up ◽  
Scan Speed ◽  
Advanced Tool

Using nanoindentation under various strain rates, the mechanical properties of a selective laser melted (SLM) SKD61 at the 800 mm/s scan speed was investigated and compared to SLM H13. No obvious pile-up due to the ratio of the residual depth (hf) and the maximum depth (hmax) being lower than 0.7 and no cracking were observed on any of the indenter surfaces. The nanoindentation strain-rate sensitivity (m) of SLM SKD61 was found to be 0.034, with hardness increasing from 8.65 GPa to 9.93 GPa as the strain rate increased between 0.002 s−1 and 0.1 s−1. At the same scan speed, the m value of SLM H13 (m = 0.028) was lower than that of SLM SKD61, indicating that the mechanical behavior of SLM SKD61 was more critically affected by the strain rate compared to SLM H13. SLM processing for SKD61therefore shows higher potential for advanced tool design than for H13.

scholarly journals Comparison of Nano-Mechanical Behavior between Selective Laser Melted SKD61 and H13 Tool Steels

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1032
Author(s):  
Jaecheol Yun ◽  
Van Nguyen ◽  
Jungho Choe ◽  
Dong-Yeol Yang ◽  
Hak-Sung Lee ◽  
...  
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Tool Steels ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Pile Up ◽  
Scan Speed ◽  
Advanced Tool

Using nanoindentation under various strain rates, the mechanical properties of a laser powder bed fusion (PBF) SKD61 at the 800 mm/s scan speed were investigated and compared to PBF H13. No obvious pile-up due to the ratio of the residual depth (hf) and the maximum depth (hmax) being lower than 0.7 and no cracking were observed on any of the indenter surfaces. The nanoindentation strain-rate sensitivity (m) of PBF SKD61 was found to be 0.034, with hardness increasing from 8.65 GPa to 9.93 GPa as the strain rate increased between 0.002 s−1 and 0.1 s−1. At the same scan speed, the m value of PBF H13 (m = 0.028) was lower than that of PBF SKD61, indicating that the mechanical behavior of PBF SKD61 was more critically affected by the strain rate compared to PBF H13. PBF processing for SKD61 therefore shows higher potential for advanced tool design than for H13.

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 Strain-Rate-Dependent Deformation Behavior and Mechanical Properties of a Multi-Phase Medium-Manganese Steel

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 344 ◽  
Author(s):  
Simon Sevsek ◽  
Christian Haase ◽  
Wolfgang Bleck
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Deformation Behavior ◽  
Rate Sensitivity ◽  
Manganese Steel ◽  
Strain Rates ◽  
Rate Dependent ◽  
Medium Manganese Steel ◽  
Multi Phase

The strain-rate-dependent deformation behavior of an intercritically annealed X6MnAl12-3 medium-manganese steel was analyzed with respect to the mechanical properties, activation of deformation-induced martensitic phase transformation, and strain localization behavior. Intercritical annealing at 675 °C for 2 h led to an ultrafine-grained multi-phase microstructure with 45% of mostly equiaxed, recrystallized austenite and 55% ferrite or recovered, lamellar martensite. In-situ digital image correlation methods during tensile tests revealed strain localization behavior during the discontinuous elastic-plastic transition, which was due to the localization of strain in the softer austenite in the early stages of plastic deformation. The dependence of the macroscopic mechanical properties on the strain rate is due to the strain-rate sensitivity of the microscopic deformation behavior. On the one hand, the deformation-induced phase transformation of austenite to martensite showed a clear strain-rate dependency and was partially suppressed at very low and very high strain rates. On the other hand, the strain-rate-dependent relative strength of ferrite and martensite compared to austenite influenced the strain partitioning during plastic deformation, and subsequently, the work-hardening rate. As a result, the tested X6MnAl12-3 medium-manganese steel showed a negative strain-rate sensitivity at very low to medium strain rates and a positive strain-rate sensitivity at medium to high strain rates.

Mechanical Anisotropy and Strain Rate Dependency Behavior of Ti6Al4V Produced Using E-Beam Additive Fabrication

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Leila Ladani ◽  
Jafar Razmi ◽  
Soud Farhan Choudhury
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Mechanical Anisotropy ◽  
Rate Dependency ◽  
Out Of Plane ◽  
Degree Of Anisotropy ◽  
Strain Rate Dependency

Anisotropic mechanical behavior is an inherent characteristic of parts produced using additive manufacturing (AM) techniques in which parts are built layer by layer. It is expected that in-plane and out-of-plane properties be different in these parts. E-beam fabrication is not an exception to this. It is, however, desirable to keep this degree of anisotropy to a minimum level and be able to produce parts with comparable mechanical strength in both in-plane and out-of-plane directions. In this manuscript, this degree of anisotropy is investigated for Ti6Al4V parts produced using this technique through tensile testing of parts built in different orientations. Mechanical characteristics such as Young's modulus, yield strength (YS), ultimate tensile strength (UTS), and ductility are evaluated. The strain rate effect on mechanical behavior, namely, strength and ductility, is also investigated by testing the material at a range of strain rates from 10−2 to 10−4 s−1. Local mechanical properties were extracted using nanoindentation technique and compared against global values (average values obtained by tensile tests). Although the properties obtained in this experiment were comparable with literature findings, test results showed that in-plane properties, elastic modulus, YS, and UTS are significantly higher than out-of-plane properties. This could be an indication of defects in between layers or imperfect bonding of the layers. Strong positive strain rate sensitivity was observed in out-of-plane direction. The strain rate sensitivity evaluation did not show strain rate dependency for in-plane directions. Local mechanical properties obtained through nanoindentation confirmed the findings of tensile test and also showed variation of properties caused by geometry.

scholarly journals On the effects of build orientation, strain rate sensitivity and sample thickness on the mechanical behavior of 316l Stainless Steel manufactured by Selective Laser Melting

2021 ◽  
Vol 250 ◽  
pp. 05009
Author(s):  
Hugo Carassus ◽  
Hervé Morvan ◽  
Gregory Haugou ◽  
Jean-Dominique Guerin ◽  
Tarik Sadat ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Selective Laser Melting ◽  
Strain Rate Sensitivity ◽  
316L Stainless Steel ◽  
Rate Sensitivity ◽  
Thickness Variation ◽  
Laser Melting

The Additive Layer Manufacturing (ALM) for metallic materials has grown in the past few years. However, this process influences the mechanical properties of the constitutive material and consequently those of the finished product. The influence of the thickness and the building direction of 316L Stainless Steel (SS) specimens produced by Selective Laser Melting (SLM) on the quasi-static mechanical behavior has already been reported. Considering the strain rate effect, it has been only studied for tensile properties of vertical specimens up to 102s–1. The aim of this work is to study the influence of the thickness and the building orientation at higher strain rates up to 101s–1 and up to 103s–1 for vertical specimens. Compared to conventional material, 316L SS SLM achieves equal and even better mechanical properties due to a refinement of the microstructure. Anisotropy is observed at the macroscopic level, which is explained by the microstructure with different shapes, orientation and size of grains. A minimum thickness of 0.75mm is recommended to recover the mechanical properties of the conventional 316L SS. A positive strain rate sensitivity is observed in every case. The material anisotropy and the thickness variation do not affect the strain rate sensitivity.

Multiscale Material Modeling and Simulation of the Mechanical Behavior of Dual Phase Steels Under Different Strain Rates: Parametric Study and Optimization

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Tarek M. Belgasam ◽  
Hussein M. Zbib
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Volume Fraction ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Dual Phase ◽  
Strain Rates ◽  
Microstructure Parameters ◽  
Dp Steels

Recent studies on developing dual phase (DP) steels showed that the combination of strength/ductility could be significantly improved when changing the volume fraction and grain size of phases in the microstructure depending on microstructure properties. Consequently, DP steel manufacturers are interested in predicting microstructure properties as well as optimizing microstructure design at different strain rate conditions. In this work, a microstructure-based approach using a multiscale material and structure model was developed. The approach examined the mechanical behavior of DP steels using virtual tensile tests with a full micro-macro multiscale material model to identify specific mechanical properties. Microstructures with varied ferrite grain sizes, martensite volume fractions, and carbon content in DP steels were also studied. The influence of these microscopic parameters at different strain rates on the mechanical properties of DP steels was examined numerically using a full micro-macro multiscale finite element method. An elasto-viscoplastic constitutive model and a response surface methodology (RSM) were used to determine the optimum microstructure parameters for a required combination of strength/ductility at different strain rates. The results from the numerical simulations were compared with experimental results found in the literature. The developed methodology proved to be a powerful tool for studying the effect and interaction of key strain rate sensitivity and microstructure parameters on mechanical behavior and thus can be used to identify optimum microstructural conditions at different strain rates.

scholarly journals Evaluation of Strain-Rate Sensitivity of Selective Laser Melted H13 Tool Steel Using Nanoindentation Tests

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 589 ◽  
Author(s):  
Van Nguyen ◽  
Eun-ah Kim ◽  
Seok-Rok Lee ◽  
Jaecheol Yun ◽  
Jungho Choe ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Tool Steel ◽  
Rate Sensitivity ◽  
Future Research ◽  
Laser Melting ◽  
H13 Tool Steel ◽  
Scan Speed ◽  
Hardness Values ◽  
Advanced Tool

This paper demonstrates the successful printing of H13 tool steel by a selective laser melting (SLM) method at a scan laser speed of 200 mm/s for the best microstructure and mechanical behavior. Specifically, the nanoindentation strain-rate sensitivity values were 0.022, 0.019, 0.027, 0.028, and 0.035 for SLM H13 at laser scan speeds of 100, 200, 400, 800, and 1600 mm/s, respectively. This showed that the hardness increases as the strain rate increases and, practically, the hardness values of the SLM H13 at the 200 mm/s laser scan speed are the highest and least sensitive to the strain rate as compared to H13 samples at other scan speeds. The SLM processing of this material at 200 mm/s laser scan speed therefore shows the highest potential for advanced tool design. Residual stress is expected to affect the hardness and shall be investigated in future research.

Effect of Strain Rates on the Mechanical Behavior of Cu Thin Films of Various Thicknesses

2013 ◽  
Vol 284-287 ◽  
pp. 94-97
Author(s):  
Kuan Jung Chung ◽  
Chi Feng Lin ◽  
W. C. Chiang
Keyword(s):  
Thin Film ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Strain Rate Sensitivity ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Tensile Testing Machine ◽  
Cu Film ◽  
Cu Thin Film

The objective of this study is to investigate the mechanical behavior of copper thin film with different thicknesses subjected to varying strain rates. A micro-force tensile testing machine (MTS Tytron 250) was used to test the polyimide samples coated with different thicknesses of copper (500 nm, 750 nm, 1000 nm, and 1500 nm). The experiments were conducted by applying test vehicles to different strain rates (1.6×10-4s-1, 1.6×10-3s-1, and 1.6×10-2s-1). The experimental results showed the strain rate and the thickness have obvious influence upon the mechanical properties of Cu thin film. The yield stress increases as increasing the strain rate or decreasing the thickness of Cu film. For considering the strain rate sensitivity m, the strain rate sensitivity m is found that it increases as decreasing the thickness to imply that Cu film has high strain-rate response at low thickness.

Strain Rate Sensitivity of Mixed SAC-SnBi Solder Joints

2019 ◽  
Vol 2019 (1) ◽  
pp. 000480-000487
Author(s):  
Luke A. Wentlent ◽  
James Wilcox ◽  
Xuanyi Ding
Keyword(s):  
Melting Point ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Solder Joints ◽  
Volume Ratio ◽  
Rate Sensitivity ◽  
Thermal Exposure ◽  
Fracture Mechanisms ◽  
Eutectic System ◽  
Strain Rates

Abstract As the electronics industry continues to evolve a concerted effort has developed to implement lower melting point solders. The ability to minimize the thermal exposure that an assembly is subjected to affords significant benefits with respect to both the reliability and the materials that can be used. One of the most popular low melt solder alloys currently being investigated by the industry is the Bi-Sn eutectic system, which has a melting point of 139°C. The BiSn system itself is not particularly novel as it was posited as a SAC alternative during the initial shift from Pb based solders. While a body of knowledge currently exists regarding this system, and the near eutectic variant BiSnAg, there are still concerns regarding its ductility, especially as a function of thermal exposure and strain rate. Bismuth is widely acknowledged as a brittle element and its presence in such quantities raises concerns of not just Cu6Sn5 embrittlement but also solder fragility in high strain rate types of environments. A challenge with regards to near term implementation is that most packages are not available with BiSn solder bumps. Therefore, it will be necessary to use components already balled with SAC 305 solder. This means that the resulting solder interconnect, reflowed below conventional SAC reflow temperatures, will form a type of mixed hybrid microstructure. This non-equilibrium microstructure will be composed of two regions, one Bi-rich region which is well past saturation and a second region which is Bi-deficient. It is of specific industrial interest then to not just investigate the BiSn solder system but also within the context of a realistic mixed interconnect. Recent work by several researchers has shown that this hybrid microstructure is unstable and quite active with respect to the movement and localized concentration of the Bismuth. The degree of mixing of these two regions has been shown to be highly dependent upon reflow temperature and the paste to ball volume ratio. Mixed SAC-BiSn solder joints were formed by placing SAC 305 spheres on BiSn paste deposits for a paste to ball volume ratio of .18. These samples were then reflowed at either 175°C or 200°C. SAC 305 control samples were also made using a conventional Pb-free reflow profile with a peak temperature of 247°C. A 22 mil Cu-OSP pad on a 1.0 mm thick FR4 substrate was used for all samples. A selection of the solder joints were then isothermally aged at 90°C for 200 hours. Using a joint level micromechanical tester, ball shear tests were conducted at a range of strain rates for samples in the as-reflowed and aged state. Using this information, the strain rate sensitivity of the interconnects was mapped and correlated with the observed failure modes. Investigations into the fracture mechanisms were conducted by examining the shear fracture surface with optical and scanning electron microscopy. Additionally, the evolution of the microstructure was characterized. Results showed a clear transition from ductile solder failure to a brittle separation failure at the higher strain rates.

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