scholarly journals Micro-Macro Relationship between Microstructure, Porosity, Mechanical Properties, and Build Mode Parameters of a Selective-Electron-Beam-Melted Ti-6Al-4V Alloy

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 786 ◽  
Author(s):  
Giovanni Maizza ◽  
Antonio Caporale ◽  
Christian Polley ◽  
Hermann Seitz
Keyword(s):  
Mechanical Properties ◽  
Electron Beam ◽  
Tensile Properties ◽  
Indentation Test ◽  
Process Conditions ◽  
Instrumented Indentation ◽  
Β Phase ◽  
Operation Modes ◽  
Melting Operation ◽  
Instrumented Indentation Test

The performance of two selective electron beam melting operation modes, namely the manual mode and the automatic ‘build theme mode’, have been investigated for the case of a Ti-6Al-4V alloy (45–105 μm average particle size of the powder) in terms of porosity, microstructure, and mechanical properties. The two operation modes produced notable differences in terms of build quality (porosity), microstructure, and properties over the sample thickness. The number and the average size of the pores were measured using a light microscope over the entire build height. A density measurement provided a quantitative index of the global porosity throughout the builds. The selective-electron-beam-melted microstructure was mainly composed of a columnar prior β-grain structure, delineated by α-phase boundaries, oriented along the build direction. A nearly equilibrium α + β mixture structure, formed from the original β-phase, arranged inside the prior β-grains as an α-colony or α-basket weave pattern, whereas the β-phase enveloped α-lamellae. The microstructure was finer with increasing distance from the build plate regardless of the selected build mode. Optical measurements of the α-plate width showed that it varied as the distance from the build plate varied. This microstructure parameter was correlated at the sample core with the mechanical properties measured by means of a macro-instrumented indentation test, thereby confirming Hall-Petch law behavior for strength at a local scale for the various process conditions. The tensile properties, while attesting to the mechanical performance of the builds over a macro scale, also validated the indentation property measurement at the core of the samples. Thus, a direct correlation between the process parameters, microstructure, porosity, and mechanical properties was established at the micro and macro scales. The macro-instrumented indentation test has emerged as a reliable, easy, quick, and yet non-destructive alternate means to the tensile test to measure tensile-like properties of selective-electron-beam-melted specimens. Furthermore, the macro-instrumented indentation test can be used effectively in additive manufacturing for a rapid setting up of the process, that is, by controlling the microscopic scale properties of the samples, or to quantitatively determine a product quality index of the final builds, by taking advantage of its intrinsic relationship with the tensile properties.

Evaluation of Tensile Properties Profile of Weld Zone Using Instrumented Indentation

2010 ◽  
Author(s):  
Seung-Kyun Kang ◽  
Young-Cheon Kim ◽  
Chan-Pyoung Park ◽  
Dongil Kwon
Keyword(s):  
Tensile Properties ◽  
Weld Zone ◽  
Indentation Test ◽  
Tensile Tests ◽  
Structural Safety ◽  
Small Scale ◽  
Stress And Strain ◽  
Instrumented Indentation ◽  
Deformation And Fracture ◽  
Instrumented Indentation Test

Understanding the property distribution in the weld zone is very important for structural safety, since deformation and fracture begin at the weakest point. However, conventional tensile tests can measure only average material properties because they require large specimens. Small-scale tests are being extensively researched to remove this limitation, among such tests, instrumented indentation test (IIT) are of great interest because of their simple procedures. Here we describe the evaluation of tensile properties using IIT and a representative stress-strain approach. The representative stressstrain method, introduced in 2008 in ISO/TR29381, directly correlates the stress and strain under the indenter to the true stress and strain of tensile testing by defining representative functions. Using this technique, we successfully estimate the yield strength and tensile strength of structural metallic materials and also obtain profiles of the weld-zone tensile properties.

A Method for Estimating Uncertainty of Indentation Tensile Properties in Instrumented Indentation Test

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Eun-chae Jeon ◽  
Joo-Seung Park ◽  
Doo-Sun Choi ◽  
Kug-Hwan Kim ◽  
Dongil Kwon
Keyword(s):  
Tensile Strength ◽  
Yield Strength ◽  
Tensile Test ◽  
Tensile Properties ◽  
Indentation Test ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Instrumented Indentation ◽  
Estimation Model ◽  
Instrumented Indentation Test

The instrumented indentation test, which measures indentation tensile properties, has attracted interest recently because this test can replace uniaxial tensile test. An international standard for instrumented indentation test has been recently legislated. However, the uncertainty of the indentation tensile properties has never been estimated. The indentation tensile properties cannot be obtained directly from experimental raw data as can the Brinell hardness, which makes estimation of the uncertainty difficult. The simplifying uncertainty estimation model for the indentation tensile properties proposed here overcomes this problem. Though the influence quantities are generally defined by experimental variances when estimating uncertainty, here they are obtained by calculation from indentation load-depth curves. This model was verified by round-robin test with several institutions. The average uncertainties were estimated as 18.9% and 9.8% for the indentation yield strength and indentation tensile strength, respectively. The values were independent of the materials’ mechanical properties but varied with environmental conditions such as experimental instruments and operators. The uncertainties for the indentation yield and tensile strengths were greater than those for the uniaxial tensile test. These larger uncertainties were caused by measuring local properties in the instrumented indentation test. The two tests had the same tendency to have smaller uncertainties for tensile strength than yield strength. These results suggest that the simplified model can be used to estimate the uncertainty in indentation tensile properties.

Multiscale Mapping of Mechanical Properties by Instrumented Indentation Test

2010 ◽  
Vol 654-656 ◽  
pp. 2316-2321
Author(s):  
Kug Hwan Kim ◽  
Young Cheon Kim ◽  
Seung Kyun Kang ◽  
Kwang Ho Kim ◽  
Dong Il Kwon
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Indentation Test ◽  
Uniaxial Tensile ◽  
Material Surface ◽  
Uniaxial Tensile Test ◽  
Instrumented Indentation ◽  
Flow Properties ◽  
Residual Stress State ◽  
Instrumented Indentation Test

The instrumented indentation test (IIT) is a mechanical testing method to determine the hardness and elastic modulus of materials by putting an indenter into a material surface. This technique has now gone beyond normal hardness tests by evaluating additional properties of materials and by allowing testing at much lower forces and indentation depths (micro/nano ranges). This study presents analytic models and procedures for evaluating tensile flow properties and residual stress state using IIT; the tensile flow properties are treated by defining a representative stress/strain beneath a spherical indenter and the residual stress by using a stress-insensitive contact hardness model. The IIT results are compared with those from conventional methods such as uniaxial tensile test and X-ray diffraction. In addition, IIT can be used as a multiscale mapping tool for the mechanical properties of composite materials and constituent phases by using macro/micro/nano indentation system: we made a hardness map of multiphase steel and measured the strength/residual stress distributions of welded pipeline.

scholarly journals Finite Element Simulation of the Instrumented Indentation Test to Estimate the Mechanical Properties for ASTM516-G70 and AISI1010 steels

2019 ◽  
Vol 34 (3) ◽  
pp. 117-129
Author(s):  
Ahmed. F. Elmisteri ◽  
Abdelbaset R. H. Midawi ◽  
Farag M Shuaeib
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Yield Strength ◽  
Finite Element Simulation ◽  
Indentation Test ◽  
Strain Curve ◽  
Instrumented Indentation ◽  
Stress Strain Curve ◽  
Element Simulation ◽  
Instrumented Indentation Test

Instrumented indentation technique at micro-scales has become more popular to determine mechanical properties of materials like hardness, modulus of elasticity, and yield strength. It is introduced as a method that finds the stress-strain curve, instead of the traditional tensile test. Furthermore, it gives a possibility to determine the mechanical properties for small specimens and material under operation in the field. Several researchers have attempted to evaluate this method experimentally and to investigate the factors affecting it by using a different shape of indenters, and different types of materials. In the same regard, this research work is conducted to evaluate this method experimentally and by finite element simulation methods. Two types of industrially significant steels were selected; they are namely ASTM516-G70, AISI1010 steel; and two shapes of indenters, blunt and sharp (Spherical, and Vickers) were used. The finite element simulation has been performed by ABAQUS simulation program, and its results were then compared with the experimental test results obtained from Nanovea instrumented indentation test machine. The results obtained have demonstrated good agreement between the experimental and the finite element simulation results within 5 % difference for young’s module, and 7.7 % for yield strength whereas excellent agreement is observed in the elastic region and the beginning of the plastic region for the engineering stress-strain curve. Finally, it is to be emphasized that the obtained results are more applicable for the tested materials, and further research is recommended to accommodate other materials as well and to confirm the generality of this method.

scholarly journals Conventional Vickers and true instrumented indentation hardness determined by instrumented indentation tests

2010 ◽  
Vol 25 (2) ◽  
pp. 337-343 ◽  
Author(s):  
Seung-Kyun Kang ◽  
Ju-Young Kim ◽  
Chan-Pyoung Park ◽  
Hyun-Uk Kim ◽  
Dongil Kwon
Keyword(s):  
Mechanical Properties ◽  
Vickers Hardness ◽  
Material Properties ◽  
Indentation Test ◽  
Indentation Hardness ◽  
Instrumented Indentation ◽  
Real Contact ◽  
Wide Range ◽  
Indentation Tests ◽  
Instrumented Indentation Test

We evaluate Vickers hardness and true instrumented indentation test (IIT) hardness of 24 metals over a wide range of mechanical properties using just IIT parameters by taking into account the real contact morphology beneath the Vickers indenter. Correlating the conventional Vickers hardness, indentation contact morphology, and IIT parameters for the 24 metals reveals relationships between contact depths and apparent material properties. We report the conventional Vickers and true IIT hardnesses measured only from IIT contact depths; these agree well with directly measured hardnesses within ±6% for Vickers hardness and ±10% for true IIT hardness.

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