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Start Over Author "Ma Qian" Journal nature communications
12 results on '"Ma Qian"'

1. Migration of solidification grain boundaries and prediction

Author

Hongmei Liu, Shenglu Lu, Yingbo Zhang, Hui Chen, Yungui Chen, and Ma Qian

Subjects
Science
Abstract

Solidification grain boundary migration (SGBM) occurs in metals and alloys manufactured by casting, welding, or 3D printing, and it affects material properties, but its mechanisms remain largely unknown. Here, the authors show how SGBM can be predicted in various alloys under different conditions.

Published
2022
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7. Metamaterial assisted illumination nanoscopy via random super-resolution speckles

Author

Lee, Yeon Ui, Zhao, Junxiang, Ma, Qian, Khorashad, Larousse Khosravi, Posner, Clara, Li, Guangru, Wisna, G Bimananda M, Burns, Zachary, Zhang, Jin, and Liu, Zhaowei

Subjects
Bioengineering, Imaging, Three-Dimensional, Microscopy, Microscopy, Fluorescence
Abstract

Structured illumination microscopy (SIM) is one of the most powerful and versatile optical super-resolution techniques. Compared with other super-resolution methods, SIM has shown its unique advantages in wide-field imaging with high temporal resolution and low photon damage. However, traditional SIM only has about 2 times spatial resolution improvement compared to the diffraction limit. In this work, we propose and experimentally demonstrate an easily-implemented, low-cost method to extend the resolution of SIM, named speckle metamaterial-assisted illumination nanoscopy (speckle-MAIN). A metamaterial structure is introduced to generate speckle-like sub-diffraction-limit illumination patterns in the near field with improved spatial frequency. Such patterns, similar to traditional SIM, are then used to excite objects on top of the surface. We demonstrate that speckle-MAIN can bring the resolution down to 40 nm and beyond. Speckle-MAIN represents a new route for super-resolution, which may lead to important applications in bio-imaging and surface characterization.

Published
2021

12. Grain structure control during metal 3D printing by high-intensity ultrasound

Author

Duyao Zhang, Mark Alan Easton, Milan Brandt, Michael Bermingham, Dong Qiu, David H. StJohn, C. J. Todaro, Ma Qian, and E. W. Lui

Subjects
Equiaxed crystals, Science, Alloy, General Physics and Astronomy, chemistry.chemical_element, Mechanical properties, 02 engineering and technology, engineering.material, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, Article, 0103 physical sciences, Ultimate tensile strength, Composite material, lcsh:Science, Anisotropy, 010302 applied physics, Multidisciplinary, General Chemistry, Metals and alloys, 021001 nanoscience & nanotechnology, Microstructure, Inconel 625, Superalloy, Nickel, chemistry, engineering, lcsh:Q, 0210 nano-technology
Abstract

Additive manufacturing (AM) of metals, also known as metal 3D printing, typically leads to the formation of columnar grain structures along the build direction in most as-built metals and alloys. These long columnar grains can cause property anisotropy, which is usually detrimental to component qualification or targeted applications. Here, without changing alloy chemistry, we demonstrate an AM solidification-control solution to printing metallic alloys with an equiaxed grain structure and improved mechanical properties. Using the titanium alloy Ti-6Al-4V as a model alloy, we employ high-intensity ultrasound to achieve full transition from columnar grains to fine (~100 µm) equiaxed grains in AM Ti-6Al-4V samples by laser powder deposition. This results in a 12% improvement in both the yield stress and tensile strength compared with the conventional AM columnar Ti-6Al-4V. We further demonstrate the generality of our technique by achieving similar grain structure control results in the nickel-based superalloy Inconel 625, and expect that this method may be applicable to other metallic materials that exhibit columnar grain structures during AM., 3D printing of metals produces elongated columnar grains which are usually detrimental to component performance. Here, the authors combine ultrasound and 3D printing to promote equiaxed and refined microstructures in a titanium alloy and a nickel-based superalloy resulting in improved mechanical properties.

Published
2019

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