In-situ synthesis of titanium aluminides by direct metal deposition

Abstract Process parameters, including deposition direction, are crucial in direct metal deposition (DMD) for microstructure formation and mechanical properties of the final part. Multi-directional deposition along with in-situ deposition control can minimize deposition anisotropy and improve dimensional accuracy. In this paper, a DMD system is developed to achieve multi-directional metal deposition by using 6 degree-of-freedom (DOF) motion of the workpiece platform rather the laser head for a highly compact design. An in-situ control strategy with two independent loops of laser focus and power is developed to control the printing process based on the feedback from real-time melt pool geometry and intensity. Experimental results have shown that the laser focus and power control can significantly improve geometrical accuracy and reduce heat accumulation. In addition, system kinematics are derived and verified for the 6-DOF hexapod to achieve multi-directional deposition. Oblique structures have been successfully printed to demonstrate the effect of optimized build direction.

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In-situ monitoring and deformation characterization by optical techniques; part I: Laser-aided direct metal deposition for additive manufacturing

Optics and Lasers in Engineering ◽

10.1016/j.optlaseng.2019.05.020 ◽

2019 ◽

Vol 122 ◽

pp. 74-88 ◽

Cited By ~ 7

Author(s):

Wei He ◽

Wenxiong Shi ◽

Jiaqiang Li ◽

Huimin Xie

Keyword(s):

Additive Manufacturing ◽

Metal Deposition ◽

Direct Metal Deposition ◽

In Situ Monitoring ◽

Optical Techniques

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SEM of non-coated hepatocellular cytoskeleton of perfused livers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111641 ◽

1984 ◽

Vol 42 ◽

pp. 306-307

Author(s):

S.W. French ◽

N.C. Benson ◽

C. Davis-Scibienski

Keyword(s):

Ambient Temperature ◽

Critical Point ◽

Protease Inhibitors ◽

Metal Deposition ◽

Heat Damage ◽

Detergent Extraction ◽

Cytoskeletal Elements ◽

Triton X ◽

Excised Tissue

Previous SEM studies of liver cytoskeletal elements have encountered technical difficulties such as variable metal coating and heat damage which occurs during metal deposition. The majority of studies involving evaluation of the cell cytoskeleton have been limited to cells which could be isolated, maintained in culture as a monolayer and thus easily extracted. Detergent extraction of excised tissue by immersion has often been unsatisfactory beyond the depth of several cells. These disadvantages have been avoided in the present study. Whole C3H mouse livers were perfused in situ with 0.5% Triton X-100 in a modified Jahn's buffer including protease inhibitors. Perfusion was continued for 1 to 2 hours at ambient temperature. The liver was then perfused with a 2% buffered gluteraldehyde solution. Liver samples including spontaneous tumors were then maintained in buffered gluteraldehyde for 2 hours. Samples were processed for SEM and TEM using the modified thicarbohydrazide procedure of Malich and Wilson, cryofractured, and critical point dried (CPD). Some samples were mechanically fractured after CPD.

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