Metallic transfer films studied in situ and ex situ: The case of cold-sprayed Al-Al2O3

The presence of A12O3 particles in the composite coating promoted the formation of nanostructured aluminum in the transfer film, which contributed to its stability, as observed by in situ tribometry. This was linked to lower wear rates and more stable friction compared to the unreinforced cold sprayed aluminum. Here, the combination of in situ tribometry and ex situ analysis was a useful approach to reveal mechanisms specifically related to the transfer film, which were responsible for improved tribological performance. Other questions remain, which will be subject of future work, regarding the microstructural evolution in the wear track, mechanical properties of the third bodies, and the role of A1203 particles in the dynamic formation of nanocrystalline aluminum.Peer reviewed: YesNRC publication: Ye

Laser welding of Ti-5Al-5V-5Mo-3Cr

Ti-5Al-5V-5Mo-3Cr butt joints were welded using a 4 kW continuous wave Nd:YAG laser. The effect of welding speed and defocusing distance on the weld quality was investigated. Welds with full penetration were achieved at a defocusing distance ranging from-1 to 0 mm and welding speeds from 2\ub725 to 6\ub70 m min -1. Underfill and porosity were the two main defects most frequently observed; however, within the optimum process window, these defects could be maintained to meet aerospace specification tolerances. The fusion zone consisted entirely of retained \u3b2 with a refined dendritic morphology. Compared with the bimodal \u3b1+\u3b2 microstructure of the base metal, dissolution of the \u3b1 phase in the heat affected zone and the presence of entirely metastable/retained \u3b2 phase in the fusion zone were observed, which led to a significant decrease in the HAZ and FZ hardness. To determine the tensile properties of the welds, an automated three-dimensional deformation measurement system was used to measure the local strain in the weld region. The yield strength and ultimate tensile strength increased with welding speed, achieving a maximum joint efficiency of 75%, albeit with a concomitant reduction in the ductility. \ua9 2011 Canadian Institute of Mining, Metallurgy and Petroleum.Peer reviewed: YesNRC publication: Ye

In situ tribometry of cold-sprayed Al-Al2O3 composite coatings

An in situ tribometer utilizing a transparent hemispherical counterface was used to conduct sliding wear tests on Al-Al2O3 composite coatings deposited by cold spray. Direct observation of the wear interface via the slider allowed for correlation to be identified between the formation of transfer film and friction changes, wear rates, and the evolution of subsurface structures. It was revealed that the presence of hard particles in the Al-Al2O3 coating stabilized the transfer film, characterized by less plastic flow and fewer instances of hole formation at the interface. This increase in stability correlated with lower wear rates, stable friction, and the formation of a mechanically mixed layer (MML) in the worn subsurface. \ua9 2012 Elsevier B.V.Peer reviewed: YesNRC publication: Ye

Global and local tensile properties of laser welded Ti-5Al-5V-5Mo-3 Cr

Peer reviewed: YesNRC publication: Ye

Temperature-dependent microtensile testing of thin film materials for application to microelectromechanical system

A specially designed microtensile apparatus capable of carrying out a series of tests on microscale thin films for microelectromechanical system (MEMS) applications at room temperature and at temperature up to 400 degrees C has been developed and tested, and is described here. Several MEMS-applicable thin films were measured with it, including thermally grown silicon dioxide, gold, and gold-vanadium. The silicon dioxide was tested at room temperature. Gold and gold-vanadium films were tested at room temperature and at 200 and 400 degrees C. Examples of these results are presented

Evidence-Based Consensus and Systematic Review on Reducing the Time to Diagnosis of Duchenne Muscular Dystrophy

Evidence-Based Consensus and Systematic Review on Reducing the Time to Diagnosis of Duchenne Muscular Dystroph