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This paper points out each key parameter involved in laser welding and discusses the parameters' effects on weld microstructure and defects detected inside the weld. Solutions are proposed to adjust the parameters to provide an optimal dental assembly. Metallurgical effects as well as defects are briefly discussed. A welding procedure adapted to different compositions of dental alloys is proposed.

An original approach based on 2D fracture surface and 3D X-ray tomography analysis is proposed in this paper. Its application in selective laser melting of Ti-6Al-4V provides substantive clarifications regarding both mechanisms of porosity formation and their influence on mechanical properties. Unambiguously, a one-toone relationship between the scanning strategy pattern and the 3D spatial distribution of porosities is highlighted. In an original manner, the 3D location of porosities, their morphology and their orientation are analyzed with respect to the laser spot path. The results show that pores are mainly localized on the overlay zones and support the lack of energy induced by the lower energy at the periphery of the laser spot as the main mechanism of porosity formation. Finally, both tensile properties and crack path are shown to be influenced by the presence and 3D distribution of porosities.

Objective: To investigate the effect of laser surface treatment of cast titanium alloy on microstructure and mechanical properties.Methods: Dumbbell-and plate-shaped cast titanium specimens were prepared for mechanical testing and microstructure analysis. After the cast surfaces of each specimen were laser-treated using a dental Nd:YAG laser machine at 240 V and 300 V with and without argon gas shielding, tensile testing and microstructure analysis were conducted.Hardness depth profiles were also made from the cross-section of laser-treated cast specimens. Microstructural and chemical analysis were performed by means of the SEM, XRD, AES and WDS.Results: The results of tensile testing and Vickers hardness depth profiling showed that laser treatment improved the mechanical properties. Bulk microstructure of as-cast titanium was mainly composed of α-grains with acicular and widmanstatten patterns.The laser melted zone was characterized by columnar beta grains. When the emission voltage of laser increased to 300 V, a larger grain size was promoted. The XRD analysis indicated that the beta phase formation was clearly noticeable after laser surface treatment. Supplementary marked peaks of the TiO, TiO 2 and Ti 2 N were detected without argon gas shielding. When argon shielding gas was used, the presence of titanium oxide was significantly reduced and the peaks of titanium nitride disappeared.Significance: Laser treatment on cast titanium surfaces showed significant enhancement of mechanical properties and modification of microstructures, and therefore could produce reliable titanium metal frameworks for dental prostheses.3

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a b s t r a c tSome novel high conductivity-high strength materials were designed in the binary Cu-Mg. They exhibit an excellent balance between strength and electrical properties. The properties and the performance of the designed materials are compared with the main Cu-based alloys and the analysis shows that they perform equally to the best one (Cu-Be). Furthermore, we show that an increase of Mg content modifies the microstructure feature and leads to a strong increase of strength without any significant deterioration of the electrical conductivity. This behavior was attributed to the formation of eutectic islands in which high density of Cu 2 Mg nanoparticles precipitate.