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A mechanical alloying and hot extrusion method was used to manufacture an Al based composite reinforced by 10 wt-% addition of Nb2O5. Annealing experiments were performed to test the effect of chemical reaction between components on the material structure. After annealing at 873 K for 12 h the material hardness was found to have increased from HB 121 (as extruded) to HB 186 (annealed). The hardness maximum was followed by material softening at prolonged aging at 873 K. Transmission electron microscopy observations revealed a very well consolidated nanoscale structure for the as extruded composite. Annealing of the material resulted in an increase in porosity that was ascribed to Nb oxide reduction by aluminium. Due to diffusion of the released Nb element into the surrounding Al matrix, formation of new intermetallic grains of Al3Nb was accompanied by very fine needlelike Al oxide particle growth within the aluminium matrix. Chemical reaction between aluminium and Nb oxide at solid state was related to local specific volume reduction being responsible for an increase in the material porosity. Hot compression tests were performed on as extruded and samples annealed at 873 K for 12 h. The good mechanical properties of the composite were ascribed to the highly refined structure of the material. In compression tests, samples were not fractured within the experimental strain range used. In hot deformation tests at lower temperatures and a strain rate of 5 10-3 s-1, some fine microcavities were observed by TEM for samples deformed to ℇt≈0·3. [ABSTRACT FROM AUTHOR]

Structural observations and hot deformation tests were carried out on mechanically alloyed Al-10 wt-%V2 O5 composite. Initial annealing experiments revealed a hardening of the material during the first stage of annealing. The material hardness increased from 114 HB for as extruded material to 167 HB after annealing at 873 K for 6 h. Differential scanning calorimetry tests conducted on as extruded material confirmed the development of an exothermic reaction during heating of the material within the temperature range 650–870 K. The amount of heat released was reduced with increasing annealing time at 873 K. Transmission electron microscopy (TEM) and X-ray analysis of annealed material revealed new intermetallic grains and very fine aluminium oxide particles, which resulted from the chemical reaction between the aluminium matrix and vanadium oxides. The development of voids in long aged specimens was found to be an undesirable effect of local specific volume reduction during the course of the chemical reaction that was not fully compensated by the local volume increase due to the growth of intermetallic particles. As a result, the material hardness was reduced in long time annealed specimens. The mechanical properties of as extruded and annealed specimens were investigated by means of hot compression testing within the temperature range 623–903 K. These tests revealed that the flow stress of as extruded material was reduced from 180 to 22 MPa when tested at 623 and 903 K, respectively. Annealed specimens exhibited higher flow stresses of 195 and 32 MPa at the same temperatures. The results indicate that the strength of the material can be effectively increased owing to a change of material structure as a result of the chemical reaction taking place during high temperature annealing. [ABSTRACT FROM AUTHOR]

A very fine structure of mechanically alloyed Al–V2O5 composite was tested by means of transmission electron microscopy and X-ray energy disperse spectrum (EDS) analysis. Annealing of the composite was found to result in the intermetallic grains growth and an increase of the material porosity due to chemical reaction between components. Hot compression tests of as extruded and annealed samples confirmed high mechanical properties of the material at high deformation temperatures that result from very fine-grained and stable structure of the composite. [Copyright &y& Elsevier]

The aim of this study was to compare the effectiveness of two diagnostic methods: ultrasonic gingival thickness measurement (UGTM) and cone-beam computed tomography, intraoral scanning by computer-aided design technology with prosthetic-driven implant planning software (CBCT/CAD/PDIP) in determining the gingival phenotype (GP). Thirty periodontally healthy patients were examined. The ultrasonic device Pirop G ® with a frequency of 20 MHz and CBCT/CAD/PDIP were used to measure gingival thickness at upper canines and incisors in three points localized midbuccally, namely free gingival thickness (FGT), supracrestal (SGT) and crestal (CGT). Probing depth (PD), clinical attachment level (CAL) and width of keratinized tissue (WKT) were measured using periodontal probe. Intra-examiner and inter-examiner agreement and agreement between methods were evaluated using Bland-Altman analyses. Comparing both methods in the determination of SGT (bias = 0.17 mm, SD = 0.25 mm, p < 0.000) and CGT (bias = -0.45 mm, SD = 0.32 mm, p < 0.000) 95.0% and 95.6% agreement were found, respectively, and in the FGT range only 93.3% (bias = -0.45 mm, SD = 0.32 mm, p < 0.000). The presence of positive correlations between WKT and SGT was shown. A positive correlation between SGT and WKT confirms the purpose of measuring these parameters for the evaluation of the GP. Both the ultrasonic method and cone-beam computed tomography combined with intraoral scanning and prosthetic-driven implant planning method were useful in determining gingival phenotype, however, the ultrasonic method was more accurate for measuring GT.

BACKGROUND Two clinical parameters, the gingival thickness (GT) and the width of keratinized tissue (WKT), describe the gingival phenotype, which is defined as the 3-dimensional volume of the gingiva. The periodontal phenotype additionally includes the thickness of the labial plate of the alveolar crest (TLPAC). MATERIAL AND METHODS Thirty patients with healthy periodontium on the upper canines and incisors underwent measurements for crestal, supracrestal, free gingival thickness (FGT), the alveolar crest-gingival margin (AC-GM), alveolar crest-cementoenamel junction distance, and the TLPAC at 2, 4, and 8 mm apically from the edge of the alveolar crest using cone-beam computed tomography (CBCT) with computer-aided design and prosthetic-driven implant planning technology. For each tooth, the gingival and periodontal phenotype was evaluated on the basis of the gingival thickness, width of keratinized tissue (WKT), and TLPAC measurements. Each patient's periodontal phenotype was evaluated according to the coronal width/length ratio of both the upper central incisors. RESULTS The dentogingival units had varying average values for the 3 periodontal phenotypes (thin phenotype: FGT 0.65±0.06 mm, WKT 4.85±1.18 mm, AC-GM 3.17±0.64 mm, TLPAC2 0.66±0.28 mm; medium phenotype: FGT 0.87±0.07 mm, WKT 5.49±1.23 mm, AC-GM 3.36±0.65 mm, TLPAC2 0.76±0.37 mm; and thick phenotype: FGT 1.20 mm, WKT 6.00 mm, AC-GM 3.90 mm, TLPAC2 0.90 mm). Positive correlations were seen among WKT, FGT, AC-GM, and TLPAC2. CONCLUSIONS Positive correlations between the FGT and WKT, and the AC-GM distance confirm that measurements using CBCT with computer-aided design and prosthetic-driven implant planning technology can evaluate the gingival phenotype and TLPAC2 for the periodontal phenotype.

A dissimilar autogenous laser welded joint of AISI 430F (X12CrMoS17) martensitic stainless steel and AISI 304 (X5CrNi18-10) austenitic stainless steel was manufactured. The welded joint was examined by non-destructive visual testing and destructive testing by macro- and microscopic examination and hardness measurements. With reference to the ISO 13919-1 standard the welded joint was characterized by C level, due to the gas pores detected. Microscopic observations of AISI 430F steel revealed a mixture of ferrite and carbides with many type II sulfide inclusions. Detailed analysis showed that they were Cr-rich manganese sulfides. AISI 304 steel was characterized by the expected austenitic microstructure with banded δ-ferrite. Martensitic microstructure with fine, globular sulfide inclusions was observed in the weld metal. The hardness in the heat-affected zone was increased in the martensitic steel in relation to the base metal and decreased in the austenitic steel. The hardness range in the weld metal, caused by chemical inhomogeneity, was 184-416 HV0.3.