Research Summary: Reducing the variations in laser welding
Objective Interactions between lasers and materials are very complex phenomena. The success of laser welding procedures in dental metals depends on the operator's control of many parameters. The aims of this study were to evaluate factors relating to the operator's dexterity and the choice of the welding parameters (power, pulse duration and therefore energy), which are recognized determinants of weld quality.Design In vitro laboratory study.Materials and methods FeNiCr dental drawn wires were chosen for these experiments because their properties are well known. Different diameters of wires were laser welded, then tested in tension and compared to the control material as extruded, in order to evaluate the quality of the welding. Scanning electron microscopy of the fractured zone and micrograph observations perpendicular and parallel to the wire axis were also conducted in order to analyse the depth penetration and the quality of the microstructure. Additionally, the micro-hardness (Vickers type) was measured both in the welded and the heat-affected zones and then compared to the non-welded alloy.Results Adequate combination of energy and pulse duration with the power set in the range between 0.8 to 1 kW appears to improve penetration depth of the laser beam and success of the welding procedure. Operator skill is also an important variable.Conclusion The variation in laser weld quality in dental FeNiCr wires attributable to operator skill can be minimized by optimization of the physical welding parameters.
LASER WELDING OF DENTAL ALLOYS: A SYSTEMATIC OVERVIEW
1 LASER WELDING OF DENTAL ALLOYS: A SYSTEMATIC OVERVIEW Shanti Varghese1, Vinaya Bhat2, Suja Joseph3, 1) Department of Prosthodontics, Noorul Islam College of Dental Sciences, Kerala University, India. 2) Department of Prosthodontics, A.B Shetty Memorial Institute of Dental Sciences, Nitte University, Mangalore, India 3) Deprtment of Prosthodontics, Pushpagiri Dental College, Peruthurithi, Thiruvalla,Kerala, India
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.