Keysight Technologies High-Temperature Nanoindentation on Pure Titanium (Ti) Application Note

Transcription

1 Keysight Technologies High-Temperature Nanoindentation on Pure Titanium (Ti) Application Note

2 Introduction Titanium (Ti) and Titanium alloys are attractive materials for high-temperature applications, e.g. for use in gas turbine engines, airframes, etc. in aerospace industry, due to their excellent high temperature stability, high strength, good corrosion and creep resistance. Chemically modifying the microstructure of titanium enhances their properties significantly, for example, some of the developed grades of titanium alloys can work at service temperatures as high as 5 C. The high strength-to-density ratio of titanium combined with their excellent elevated mechanical properties makes it a competitive candidate with commonly used nickel-based superalloys and stainless steels in similar applications. Recent development in the hightemperature nanoindentation provided the ability of examining the elevated near-the-surface mechanical properties of Titanium in a much faster and easier way, which facilitates precise local measurements over the large surface of testing material to obtain more reliable and statistically significant data. The G2 laser heater is the world s most flexible, and user-friendly instrument for hightemperature nanoscale mechanical testing. It uses laser as a very fast heating method to provide accurate and stable testing conditions for elevated nanoindentation. Advantages include the ability to measure various nanomechanical properties, e.g. hardness and modulus at precisely controlled temperatures up to 5 C (.1 C accuracy). To ensure reliable data, the system minimizes contact thermal drift by simultaneously heating the tip using laser heater. The system is also fully integrated with NanoSuite software and compatible with various methods including dynamic measurements enabled by Continuous Stiffness Measurement (CSM) option. In this study, the mechanical properties of commercially pure Ti was evaluated at ambient temperature (2 C) and elevated temperatures up to 5 C using the laser heater combined with CSM method to accurately examine the depth and temperature dependence of Ti at various temperatures. Test Methodology Sample surface of commercially available pure Ti was mechanically polished for nanoindentation test. The sample was mounted in a specially designed laser heater stage equipped with a thermocouple attached to the sample to report the exact temperature during the test in situ. Then the stage was moved below the XP indenter (diamond berkovich) designed to be also heated by laser to the desired testing temperature. A fine thermocouple was also attached to the indenter tip for the most accurate measurements of tip temperature, which is in consistent with the sample temperature for contact drift minimization. Testing temperatures and the rate of heating for both sample and tip are controlled by laser heater control software. Standard CSM method was used for temperatures starting from 2 C and going up to 2 C, 4 C, 45 C and 5 C. For each testing condition, 9 measurements were performed and the data were averaged over all data points.

3 3 Keysight High-Temperature Nanoindentation on Pure Titanium (Ti) - Application Note Elevated nanoindentation on pure Ti at a wide range of temperatures Figure 1 compares load, young modulus and hardness in different indentation depth for Ti at various testing temperatures. (a) Load On Sample (mn) Load On Sample vs Displacement Into Surface Ti 2C Ti 2C Ti 4C Ti 45C Ti 5C (b) Modulus vs Displacement Into Surface Modulus Ti 2C Ti 2C Ti 4C Ti 45C Ti 5C (c) Hardness Hardness vs Displacement Into Surface Ti 2C Ti 2C Ti 4C Ti 45C Ti 5C Figure 1. a) Load b) Young s Modulus and c) Hardness at different indentation depth for pure Ti at room and elevated temperatures using G2 laser heater system and Continuous Stiffness Measurement (CSM) method. Results show a significant decrease in the load, Young s modulus and hardness with increasing temperature as expected. As mentioned, all curves are averaged over 9 data series for each test temperature. It can be seen that beyond 5 nm depth, hardness and modulus are constant.

4 4 Keysight High-Temperature Nanoindentation on Pure Titanium (Ti) - Application Note Young's Modulus Young s Modulus.5 Hardness Temperature ( C) Hardness Figure 2. Young s modulus and hardness of Ti as a function of Temperature. Figure 2 shows the hardness and modulus for all test temperatures, averaged over the depth range of 5-17 nm and values are summarized in Table 1. It shows that at 2 C, the mechanical properties of Ti are maintained as there is not a significant change compared with the room temperature properties. But as temperature goes up to 4 C, there is a sharp drop in these values due to softening behavior of Ti at elevated temperatures. Table 1. Comparison of hardness and modulus of Ti at different temperatures. Temperature (ºC) Young's Modulus Std. deviation Hardness Std. deviation Conclusions High-temperature mechanical properties of Pure Titanium was successfully tested by G2 laser heater over a range of temperatures from ambient to 5 C. Results accurately report the temperature dependence of Ti mechanical properties and the threshold beyond which the mechanical properties drop significantly due to the microstructural changes by high-temperature material softening.

5 5 Keysight High-Temperature Nanoindentation on Pure Titanium (Ti) - Application Note Acknowledgement The investigation of this paper was carried out by D. Bedorf and M. Knieps at the SURFACE NanoLab, Hückelhoven, Germany. For more information on Keysight Technologies products, applications or services, please contact your local Keysight office. The complete list is available at: Evolving Since 1939 Our unique combination of hardware, software, services, and people can help you reach your next breakthrough. We are unlocking the future of technology. From Hewlett-Packard to Agilent to Keysight. Americas Canada (877) Brazil Mexico United States (8) Asia Pacific Australia China Hong Kong India Japan 12 (421) 345 Korea Malaysia Singapore Taiwan Other AP Countries (65) Europe & Middle East Austria Belgium Finland France Germany Ireland Israel Italy Luxembourg Netherlands Russia Spain Sweden Switzerland Opt. 1 (DE) Opt. 2 (FR) Opt. 3 (IT) United Kingdom For other unlisted countries: (BP ) This information is subject to change without notice. Keysight Technologies, 217 Published in USA, October 26, EN