Narrow Results

It is known that the press formability and the elongation of laser textured sheet are improved, and the service life of textured roll is longer than that of the un-textured roll due to hardening of the treated surface. One of the goals to develop high repetitive rate YAG laser-induced discharge texturing (LIDT) is to get deeper hardening zone. By observing and measuring cross-section of LIDT spots in different discharge conditions, it is found that the single-crater, which is formed by the discharge conditions of anode, which is covered by an oil film and with rectangular current waveform, has the most depth of heat affected zone (HAZ) comparing with other crater shapes when discharge energy is the same. The depth of HAZ is mainly depends on pulse duration when the discharge spot is single-crater. The results are analyzed.

Laser Beam cutting is a type of non-conventional machining process in which the removal of materials takes place due to the melting and vaporization of material when the laser beam comes in contact with it. This work examines the impact of the cut quality characteristics of the SS347 material and to find reduced surface roughness, machining time and heat affected zone by laser beam cutting. The cutting process was assisted by CO₂ gas pressure. Power, standoff distance, speed and CO₂ gas pressure are the cutting parameters considered for this study and the output parameters measured are machining time, heat affected zone and surface roughness. In accordance with L-9 orthogonal arrays, the experiments were planned. Analysis of Variance has been used to study how input functions influence output functions which revealed that speed (59.75% and 89.75%) is the significant factor for machining time and surface roughness while power (91.27%) was the dominant factor for heat affected zone. Gas pressure did not have much influence in the output parameters. The mathematical expressions of the output are used as input for the multi-objective function of the genetic algorithm. Optimal solutions are compared to hybrid and without-hybrid functions. It is found that the hybrid function shows a higher performance compared to the without hybrid function.

Laser beam percussion drilling (LBPD) can create high density holes in aerospace materials with the repeated application of laser pulses at a single spot. In this study, one-parameter-at-a-time approach has been used to investigate the individual effect of peak power, pulse width and pulse frequency on geometrical accuracy and metallurgical distortion during LBPD of 0.85mm thick Ti–6Al–4V sheet using 200W Yb:YAG fiber laser. It has been found that the output parameters behave differently at the higher and lower values of a particular input process. The increase of pulse width from 1 to 1.50ms increases hole taper by 20% whereas the same corresponding change from 1.50 to 2.00ms reduces the taper by 20%. The increase of pulse frequency from 10 to 50Hz reduces hole circularity by 40% but the same proportionate change from 50 to 90Hz reduces circularity by 79%. Increase of peak power from 1.70 to 2.0kW increases hole taper by 8% but the corresponding increase from 2 to 2.30kW is 143%.

Laser powder bed fusion (L-PBF) is promising for producing metallic glasses (MGs) for its extremely high cooling rate and ability to manufacture complex geometrical components. However, the crystallization of MGs under different L-PBF parameters is not fully investigated, which has influences on the mechanical properties. In this study, we develop a multi-physics thermal-fluid flow model for the L-PBF process of MGs, run simulation cases for single tracks, and then analyze the molten pool morphology and crystallization behavior in the center and edge of the track, as well as the heat affected zone. The simulation results are validated against the experimental results in the literature and have provided deeper insight into the crystallization phenomenon observed in the experiments.

The effect of helium on the irradiation damage characteristics and radiation induced segregation at grain boundaries in the welding heat affected zone (HAZ) of Fe-Cr-Mn(W,V) alloy for fusion-fission mixed reactor were investigated by high voltage electron microscopy connected with a high energy ion accelerator. Experimental results showed that the helium enhanced formation of dislocation loop and of void nuclei from initial stage of irradiation, so that void swelling was increased. Furthermore the concentration of solute atoms of Cr, Mn decreased and concentration change of Ni, V, Si, W at grain boundaries were suppressed effectively. The HAZ of Fe-Cr-Mn(W,V) alloy has superior resistance for irradiation damage under existence of helium.

The following sections are included:

• Introduction

• Experimental Methods
  • Time Resolved Diffraction Measurements
  • Preparation of Combustion Synthesis Specimens
  • Temperature Profile Measurements
  • Spatially Resolved X-ray Diffraction (SRXRD) Measurements
  • Titanium Samples for Welding
  • Welding Setup and Procedure

• Results
  • Time Resolved Diffraction Data
    • The Synthesis of TaC
    • The Synthesis of Ta₂C
    • Temperature Profiles of the Combustion Front
  • Spatially Resolved X-ray Diffraction Data
    • Phase Mapping in the HAZ of Ti Fusion Welds
    • The α Pattern
    • The α_AR Pattern
    • The α_RG Pattern
    • The α_BT Pattern
    • The β Pattern

• Discussion
  • Combustion Reaction Temperature
  • Chemical Dynamics of the Ta-C Combustion Synthesis
  • Thermal Distribution in a Ti Fusion Weld
  • The α_AR Pattern: Location and Associated Microstructure
  • The α_RG Pattern: Location and Associated Microstructure
  • The β and β_L Pattern: Location and Associated Microstructure
  • The α_BT Pattern: Location and Associated Microstructure

• Concluding Remarks

• Acknowledgments

• References