RESUMEN
Ultrasonic velocity and attenuation measurements in AZ91D magnesium (Mg) alloy with dendritic, rosette and globular microstructures were performed at elevated temperatures using a non-contact laser-ultrasonic technique. It was found that the ultrasonic velocity in the globular microstructure and the ultrasonic attenuation in the dendritic microstructure are the highest among the three microstructures. An ultrasonic clad steel buffer rod sensor embedded in the die has been used to monitor the semi-solid die casting process in-line for the AZ91D Mg alloy. This probe monitored the completion of the die filling, the release of the pressure, the opening of the die, part detachment, solidification of the part, the averaged temperature of the die and the part.
RESUMEN
A chemical etching technique is described for producing etch patterns in beryllium-free nickel chromium ceramo-metal alloy. Disc-shaped samples were chemically etched, evaluated with SEM and analysed by the EDAX technique. Scanning electron micrographs revealed, profound retentive cavities. The EDAX analysis provided a comprehensive interpretation of the etch mechanism. The obtained results show that the developed chemical etching has the potential to produce a highly retentive etched surface with less problematic and less technique sensitive than electrolytic etching.
Asunto(s)
Grabado Ácido Dental/métodos , Berilio , Aleaciones de Cromo/análisis , Microanálisis por Sonda Electrónica/métodos , Aleaciones de Cerámica y Metal/análisis , Técnica de Colado Dental , Geles , Ácido Fluorhídrico , Microscopía Electrónica de Rastreo , Propiedades de SuperficieRESUMEN
The effect of the technique used for impression making on the accuracy of three types impression materials, (vinyl silicons, condensation silicons and polyether elastomers) was evaluated. Three main impression making techniques were used. Impressions were made for stainless steel master model. The impressions were poured after thirty minutes with improved stone into stone casts. Accuracy was assessed by comparing seven measurements of the master model to their corresponding on the stone case produced. A travelling microscope of 0.001 mm accuracy was used for measurements. The results of the study have shown that all elastomeric impression materials produced accurate impression but with significant difference among them. The polyether was more accurate than silicon impressions. The technique used for making the impression had more effect on the relative accuracy than the type of the material. Reference for the best technique for each type was concluded.
Asunto(s)
Materiales de Impresión Dental/normas , Técnica de Impresión Dental , Elastómeros de Silicona/normas , Compuestos de Vinilo/normas , Resinas Acrílicas , Técnica de Impresión Dental/instrumentación , Técnica de Impresión Dental/estadística & datos numéricos , Ensayo de Materiales/métodos , Ensayo de Materiales/estadística & datos numéricosRESUMEN
In this study the SEM was used to measure the axial and marginal gap distance and to declare the marginal openings and faulty castings of three different ceramometal alloys a precious, semi-precious and nonprecious alloy systems that are commercially used in crown and bridge prosthodontics and to make a comparison between them in regard to axial and marginal gap distance.