iy Fundamental Investigations for Residual Stress Measurements in the 
x Micrometer Range by means of the Correlation of Magnetic Quantities to 
b Experimentally Determined Stress-Strain Fields 
i [. Altpeter, S. Kühn, M. Kopp, W. Arnold, M. Kréning, Fraunhofer-Institute IZFP, Saarbruecken, 
a Germany; M. Zehetbauer, Institute for Material Physics, Vienna, Austria 
1 
leskompengy 
sersaldrehigy 
un ff I. Abstract 
ron 
Hessen und hy Increasing miniaturization of micromechanic and microelectronic components has directed 
Dri intensified attention to residual stress measurements with high lateral resolutions. The fundamentals 
prt, 4 for a quantitative method to measure residual stresses in the micrometer range, which is less time- 
os consuming and less expensive than X-ray methods, was developed within the framework of a DFG 
Cir research program. For the first time, the Barkhausen Noise Eddy Current Microscope (BEMI) offers 
ehtun ir Kono a powerful testing technique that can be used (adequate calibration provided) for non-contact, high- 
pasty li resolution residual stress measurements in the micrometer (Lum) range. 
ehfisch, Einrie 
onoskopie, Hi 
She 2. Objective and Solution 
Vestn, dio 
Biron} The objective of the research work was the establishment of fundamentals for quantitative residual 
1 Brechushimessm stress measurements in the micrometer (um) range that takes less time and cost less than 
conventional X-ray methods. The investigations for this research project were performed using the 
Barkhausen Noise Eddy Current Microscope (BEMI, developed by IZFP) that detects magnetic 
material properties in the micrometer range (see Chapter 3.3 below). Nickel specimens, coarse- 
grain annealed to enlarge the grain and to reduce residual stresses, were used for the experiments. 
To apply a defined residual stress state to the material in the elastic range, the specimens were 
subjected to a tensile testing machine. The amount of residual stresses was verified with 
electromagnetic methods and the X-ray Bragg Peak Profile Analysis technique for each specimen. 
Despite the long times required for data acquisition, and the X-ray analysis to determine stress 
fields inside the grain and local dislocation density, the line-profile analysis was still indispensable 
as a reference method. 
3. Investigation Methods 
3.1 Back-Scatter Electron Diffraction 
The location of individual grains, which is relative to the tension axis and corresponds to the 
magnetization direction and to the surface normal, effects Barkhausen Noise and eddy current 
signals. The grain orientation characteristic, which yields the easy direction of the spontaneous 
magnetization (111 for nickel), is a very important factor for the interpretation of micromagnetic 
measurements. Also, the assignment of the reflections recorded by the X-ray Bragg Peak Profile 
Analysis (XPA) technique to individual crystallites would not be possible without metallurgic 
reproductions. The orientation of the grains was determined by Electron Back Scatter Diffraction 
(EBSD) and Orientation Imaging Microscopy (OIM) techniques. The EBSD indicates the 
diffraction of back-scattered electrons from the primary electron-beam on a heavily tilted sample. 
High lateral resolution (approximately 200nm) and high orientation accuracy (+2° for absolute 
measurements) are the most important advantages. References [2] and [3] refer to detailed 
information about data acquisition operations. 
99