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.

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 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.

Mechanical properties of nanophase TiO2 as determined by nanoindentation

1990 ◽  
Vol 5 (5) ◽  
pp. 1073-1082 ◽  
Author(s):  
M. J. Mayo ◽  
R. W. Siegel ◽  
A. Narayanasamy ◽  
W. D. Nix
Keyword(s):  
Strain Rate ◽  
Single Crystal ◽  
Young’S Modulus ◽  
Strain Rate Sensitivity ◽  
Sintering Temperature ◽  
Young's Modulus ◽  
Rate Sensitivity ◽  
Ceramic Materials ◽  
Microstructural Inhomogeneity ◽  
Hardness Values

Nanoindenter techniques have been used to determine the hardness. Young's modulus, and strain rate sensitivity of nanophase TiO2, which is currently available only in very small quantities and which cannot be tested by most conventional techniques. Hardness and Young's modulus both increase linearly with sintering temperature over the range 25–900°C but come to within only 50–70% of the single crystal values. Strain rate sensitivity, on the other hand, is measurably greater for this material than for single crystal rutile, and the value of strain rate sensitivity increases as the grain size and the sintering temperature are decreased. In its as-compacted form, the strain rate sensitivity of nanophase TiO2 is approximately a quarter that of lead at room temperature, indicating a potential for significant ductility in these ceramic materials. Finally, a significant scatter in hardness values has been detected within individual nanophase samples. This is interpreted as arising from microstructural inhomogeneity in these materials.

Raster scan selective laser melting of the surface layer of a tool steel powder bed

2005 ◽  
Vol 219 (4) ◽  
pp. 379-384 ◽  
Author(s):  
T H C Childs ◽  
C Hauser
Keyword(s):  
Selective Laser Melting ◽  
Tool Steel ◽  
Laser Energy ◽  
Steel Powder ◽  
Beam Diameter ◽  
Laser Melting ◽  
Powder Bed ◽  
H13 Tool Steel ◽  
Scan Speed ◽  
The Masses

Square areas, 15 mm × 15 mm in size, have been melted in the surface of powder beds made from H13 tool steel, using a raster-scanning CO2 laser focused to a beam diameter of 0.6 mm. Laser powers from approximately 50 to 150 W and scan speeds from 0.5 to 300 mm/s have been used, at two scan spacings, 0.15 mm and 0.45 mm. The appearances of the layers in the different conditions, dense or porous, have been observed by low-magnification scanning electron microscopy. The masses of the layers have been measured and simulations have been carried out to predict the masses. The variation of mass with scan speed, at a constant laser power, has been found to be much less than might be expected from a constant absorptivity of laser energy into the bed. The simulations suggest that absorptivities range from 0.25 to approximately 1.0 and that, during any one scan, heating of the bed by previous scans must be considered in order even partially to explain the observations. The work is relevant to attempts to build metal parts without supports, by selective laser melting.

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.

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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