ADAPT’s advanced characterization center enables leading-edge research of the complex process structure-property relationships in AM parts. The center’s capabilities are complemented by a variety of selective laser melting and directed energy deposition machines owned by our members and include:
- Intelligent materials database
- 3D X-ray tomography (CT) and grain mapping
- Phase and structure analysis
- Residual stress and texture mapping
- Thermomechanical testing
- Optical metrology
- CT particle analysis
- X-ray diffraction development
The Zeiss Xradia Versa 3D X-ray microscope enables cutting-edge, nondestructive tomographic imaging and grain reconstruction. X-ray tomography (μ-XCT) allows for the collection of both surface and internal renderings, which are used to distinguish between phases and identify defects such as porosity that impact the performance of additively manufactured parts. Nondestructive diffraction contrast tomography (DCT) provides direct 3D crystallographic grain reconstructions for crystalline materials.
The ADAPT Advanced Characterization Center offers the unique ability to first nondestructively characterize pore distributions in sample parts using the Zeiss Xradia Versa, then to mechanically test those same parts using the load frames described below to correlate defect structures and mechanical behavior.
- Absorption contrast tomography: resolution to 0.7 µm; up to 160 kV to probe metallic samples up to 4 mm in diameter; automated center shift and reconstruction; automated ring artifact elimination
- Phase contrast tomography: improved resolution at phase boundaries to distinguish particle dispersions
- Dual-energy tomography: low- and high-energy scans allow for segmentation based on differential X-ray absorption
- Diffraction contrast tomography: grain mapping provides crystallographic orientation of samples; grain size approximation enables the preparation of samples for synchrotron experiments
The MTS 370.02 increases loading complexity by combining simultaneous axial and torsional loading. It has a load capacity of 25 kN and is capable of testing tension, compression, fatigue and torsion. The crystallographic texture and nonequilibrium nature of AM part microstructures result in unusual, anisotropic mechanical behavior that can affect the performance of AM parts placed under complex, multidirectional loading. The MTS 370.02 facilitates the understanding of the relationships between microstructure and final properties.
- 25 kN load capacity
- Biaxial loading enables examination of the 2D yield surface
- Combine with 3D DIC (digital image correlation) to measure in- and out-of-plane strain
- Visually program complex static, quasi-static and dynamic loading, including dwell and cyclic loading
The MTS 370.10 provides high-fidelity uniaxial mechanical data on additively manufactured standard tensile test specimens for larger, structural materials. When combined with the composition- and orientation-related degrees of freedom available in metals 3D printers, this load frame provides an invaluable comparison of tension, compression and fatigue test data for AM parts with the extensive test data available for traditionally manufactured parts.
- 100 kN load capacity
- Cooled grips for future in situ, high-temperature mechanical testing
- Alignment fixture ensures compliance with ASTM E1012, GES400 (NADCAP), GE450 and ISOTC 164SC5WG11
The Mark 10 electromechanical load frame is a small, benchtop load frame that is easily configurable for tensile, compressive and cyclic testing of samples. It is well suited to characterize 3D-printed compression cylinders imaged with the Zeiss Xradia Versa. By combining the tomographic imaging capabilities of the Zeiss and the mechanical testing abilities of the Mark 10, we can get a unique glimpse into the mechanical properties of a 3D-printed sample as well as the structure responsible for those properties and the process that produced that structure.
- Force measurements up to 6.7 kN
- 5 N load resolution for 2 mm OD compression cylinders
- Optical table mount for 3D DIC (digital image correlation) strain measurements
- Load cells, grips and fixtures for compression and tension
MTS Biaxial Load Frame
The custom biaxial load frame in the ADAPT Advanced Characterization Center is a one-of-a-kind load frame that allows us to fully explore the effect of multidirectional loading. It can produce arbitrary biaxial loading—tension-tension, tension-compression, and compression-compression—to accurately replicate the widest range of in-service loading conditions.
- Fully independent, 25 kN, orthogonal loading axes
- Transportable at 1.3 m wide, 1.3 m high, 0.3 m deep and less than 275 kg
- Less than 5 µm procession of the rotation axis under full load
- Designed in collaboration with synchrotron beam line scientists at Argonne National Laboratory to collect far-field high-energy diffraction microscopy (ff-HEDM) data during loading operations
- Concentricity and angularity calibration fixtures on all four hydraulic actuators
Digital Image Correlation System
All strain measurements in the lab are performed using digital image correlation (DIC). DIC is a noncontact optical strain measurement technique. Samples are speckled and a series of images is captured at a fixed frequency using high-resolution cameras synchronized with the load frame. The VIC 3D and ARAMIS software packages are used to analyze the images and compute strain measurements.
- Macroscopic and microscopic lenses for large and small sample areas, respectively
- Image resolution options between VGA (640 x 480) and QXGA (2048 x 1536)
- Measured strain accurate to better than 0.1 microstrain
Optical microscopy is a cornerstone of metallurgical materials analysis. The advanced image processing capabilities of the Keyence VHX-5000 enable 3D reconstruction of the surface of AM parts, which can be used to compare the printed part to the original part design. When combined with metallurgical analysis, the library of 1D and 2D measurement tools can be used to quantify phases, voids and other structural features. Differential interference contrast and polarized light microscopy expose features in polished and etched metallurgical samples that reveal details about grain growth, microstructural evolution and compositional segregation in as-printed and solution-annealed Inconel 718.
- 20–5000X magnification
- Bright field and dark field lighting configuration
- Polarized/cross-polarized lighting
- Differential image contrast
- 50 frame-per-second image processing to produce an infinite depth of field, even at high magnifications
- 2D stitching to image large areas at high resolution
- 3D stitching to measure height profiles across large areas
- Semiautomated grain segmentation, grain shape and grain statistics
- Profilometry measurements
The Panalytical Empyrean X-ray diffractometer provides crystallographic and compositional information critical to understanding the mechanical performance of 3D-printed parts. Through small- and wide-angle X-ray scattering (SAXS/WAXS), its ability to test samples at temperatures ranging from -200 °C to 1100 °C, and capture of information on texture, residual stress and pair distribution functions, the Panalytical Empyrean demonstrates how the crystal structure of 3D-printed metals changes during operation at high and low temperatures, a significant concern in aerospace. Residual stress and texture are major concerns in as-printed metals and affect both structural conformity and mechanical behavior. Along with the crystallographic information that X-ray diffraction provides, compositional variations in additively manufactured parts are often far from the equilibrium phases predicted in phase diagrams. The properties of phases found in the as-printed part, and the change in those properties as those phases transform in service, is crucial information when designing for AM.
- Cu and Mo radiation for low- and high-energy XRD
- Reflection/transmission geometry with rotating sample for improved statistics
- Spinning capillary
- Bragg–Brentano optics and focusing geometry
- Residual strain measurements
- Cu/Mo focusing mirror and monocapillary 100 µm beam for microdiffraction
- 5-axis Eulerian cradle for texture mapping
- Grazing incidence XRD
- Pair distribution function
- Galipix 3D area detector
- In situ stages from -200 to 1100 °C (-328 to 2012 °F)