Application Note | Metallurgical Nanoindentation
Metallurgy Study of a Multiphase Material Using Nanoindentation
Pinpointing Individual Phases for Hardness and Young’s Modulus with an Advanced Stage Controller
Research & Experimental Testing
Duanjie Li & Alexis Celestin
Visual Design & Editorial
Andrew Shore
Introduction
Metallurgy studies the physical and chemical behavior of metallic elements, as well as their intermetallic compounds and alloys. Metals that undergo working processes, such as casting, forging, rolling, extrusion and machining, experience changes in their phases, microstructure and texture. These changes result in varied physical properties including hardness, strength, toughness, ductility, and wear resistance of the material. Metallography is often applied to learn the formation mechanism of such specific phases, microstructure and texture.
Why Local Mechanical Properties Matter for Materials Design
Advanced materials often have multiple phases in a special microstructure and texture to achieve desired mechanical properties for target applications in industrial practice. Nanoindentation is widely applied to measure the mechanical behaviors of materials at small scalesi, ii. However, it is challenging and time-consuming to precisely select specific locations for indentation in a very small area. A reliable and user-friendly procedure of nanoindentation testing is in demand to determine the mechanical properties of different phases of a material with high precision and timely measurements.
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Measurement Objective
In this application, we measure mechanical properties of a multiphase metallurgical sample using the Most Powerful Mechanical Tester: the NANOVEA PB1000.
Here, we showcase the capacity of the PB1000 in performing nanoindentation measurements on multiple phases (grains) of a large sample surface with high precision and user friendliness using our Advanced Position Controller.
NANOVEA PB1000 Large Platform
Mechanical Tester
Test Conditions
In this study, we use a metallurgical sample with multiple phases. The sample had been polished to a mirror-like surface finish before the indentation tests. Four phases have been identified in the sample, namely Phase 1, Phase 2, Phase 3 and Phase 4 as shown below.
The Advanced Stage Controller is an intuitive sample navigation tool which automatically adjusts the speed of sample movement under the optical microscope based on position of the mouse. The further the mouse is away from the center of field of view, the faster the stage moves toward the mouse’s direction. This provides a user-friendly method to navigate the entire sample surface and select the intended location for mechanical testing. The coordinates of the test locations are saved and numbered, along with their individual test setups, such as loads, loading/unloading rate, number of tests in a map, etc. Such a test procedure allows users to examine a large sample surface for specific areas of interest for indentation and perform all the indentation tests at different locations in one time, making it an ideal tool for mechanical testing of metallurgical samples with multiple phases.
In this study, we located the specific phases of the sample under the optical microscope integrated in the NANOVEA Mechanical Tester as numbered on Fig. 1. The coordinates of the selected locations are saved, followed by automatic nanoindentation tests all at once under the test conditions summarized below.
| Parameter | Value |
|---|---|
| Maximum force | 50 mN |
| Loading rate | 100 mN/min |
| Unloading rate | 100 mN/min |
| Creep | 5.0 s |
| Computation method | ASTM E2546 & Oliver & Pharr |
| Indenter type | Berkovich |
Test conditions of the nanoindentation.
Results: Nanoindentations on Different Phases
The indentations at the different phases of the sample are displayed below. We demonstrate that the excellent position control of the sample stage in the NANOVEA Mechanical Tester allows users to precisely pinpoint the target location for mechanical properties testing.
The representative load-displacement curves of the indentations are shown in Fig. 2, and the corresponding hardness and Young’s Modulus calculated using Oliver and Pharr Methodiii are summarized and compared in Fig. 3.
The Phases 1, 2, 3 and 4 possess an average hardness of ~5.4, 19.6, 16.2 and 7.2 GPa, respectively. The relatively small size for Phase 2 contributes to its higher standard deviation of the hardness and Young’s Modulus values.
| Phase | Average hardness (GPa) |
|---|---|
| Phase 1 | ~5.4 |
| Phase 2 | ~19.6 |
| Phase 3 | ~16.2 |
| Phase 4 | ~7.2 |
Table 1: Average hardness of the four phases.
Conclusion
In this study, we showcased the NANOVEA Mechanical Tester performing nanoindentation measurements on multiple phases of a large metallurgical sample using the Advanced Stage Controller. The precise position control allows users to easily navigate a large sample surface and directly select the areas of interest for nanoindentation measurements.
The location coordinates of all the indentations are saved and then performed consecutively. Such a test procedure makes measurement of the local mechanical properties at small scales, e.g. the multi-phase metal sample in this study, substantially less time-consuming and more user friendly. The hard Phases 2, 3 and 4 improve the mechanical properties of the sample, possessing an average hardness of ~19.6, 16.2 and 7.2 GPa, respectively, compared to ~5.4 GPa for Phase 1.
The Nano, Micro or Macro modules of the instrument all include ISO and ASTM compliant indentation, scratch and wear tester modes, providing the widest and most user friendly range of testing available in a single system. NANOVEA’s unmatched range is an ideal solution for determining the full range of mechanical properties of thin or thick, soft or hard coatings, films and substrates, including hardness, Young’s modulus, fracture toughness, adhesion, wear resistance and many others.
References
i. Oliver, W. C.; Pharr, G. M., Journal of Materials Research, Volume 19, Issue 1, Jan 2004, pp. 3–20
ii. Schuh, C. A., Materials Today, Volume 9, Issue 5, May 2006, pp. 32–40
iii. Oliver, W. C.; Pharr, G. M., Journal of Materials Research, Volume 7, Issue 6, June 1992, pp. 1564–1583
Frequently Asked Questions About Nanoindentation of Multiphase Metals
Why measure the mechanical properties of individual phases?
Working processes such as casting, forging, rolling, extrusion and machining change a metal’s phases, microstructure and texture, and advanced materials often rely on multiple phases to reach their target properties. Measuring each phase shows how it contributes to hardness, strength, toughness, ductility and wear resistance.
What makes nanoindentation of individual phases difficult?
It is challenging and time-consuming to precisely select specific locations for indentation in a very small area. A reliable, user-friendly procedure is needed to test different phases with high precision in a timely way.
How are indentation locations selected on the sample?
The Advanced Stage Controller moves the stage under the integrated optical microscope at a speed set by the mouse position, faster the further the mouse is from the center of the field of view. Test locations are saved and numbered with their own setups, and all indentations then run automatically in one go.
What hardness did the four phases show?
Phases 1, 2, 3 and 4 had average hardness of ~5.4, 19.6, 16.2 and 7.2 GPa, calculated with the Oliver and Pharr method. The small size of Phase 2 contributes to the higher standard deviation of its hardness and Young’s modulus.
What test conditions were used?
A Berkovich indenter loaded to 50 mN at 100 mN/min with a 5.0 s creep and unloading at 100 mN/min, computed per ASTM E2546 and the Oliver and Pharr method, on a sample polished to a mirror-like finish.
Which NANOVEA instrument was used for this metallurgy study?
The NANOVEA PB1000 Mechanical Tester with its integrated optical microscope and Advanced Stage Controller. Its Nano, Micro and Macro modules include ISO and ASTM compliant indentation, scratch and wear modes.
