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[en] The studies of mechanical property, microstructure evolution and fracture analysis in pure titanium processed by torsion deformation at 298, 673 and 1073 K are conducted systematically. The variations of mechanical property of deformed pure titanium are shown through Vickers hardness evaluation. During torsion at 298 K, the grains are refined and elongated, but the α phase with different shapes precipitates for twisted samples at 673 and 1073 K. The fracture appearance indicates that the elongated dimples occur on fracture surface at 298 K. Besides, a large number of shear facets are arranged. However, typical intergranular fracture appearance with lots of blocks in polyhedral shape covers the fracture surface at 673 and 1073 K, respectively.
[en] The influences of temperature and duration of tempering on hardness and microstructure were investigated at high-temperature martensitic and low-carbon steels with 9% chrome and the further alloying elements molybdenium, vanadium, niobium and partially tungsten. After austenitizing and subsequent air cooling the steels were tempered at temperatures below, at and above Ac1b for different times and finally a hardness test was performed. Making use of the temperature dependence of the hardness tempering diagrams were constructed and the Hollomon-Jaffe-Parameter on the three steels was determined within its application limits. Micrographs of the structure shows the formation of the carbides and the martensite. At tempering temperatures below Ac1b a decrease of hardness occurs, above Ac1b, a hardness rise due to the partial austenitizing was obtained. While hardening below Ac1b, the tempering quality increases from P 91, NF 616 to E 911. (orig.)
[de]An warmfesten martensitischen Staehlen mit niedrigem Kohlenstoffgehalt, 9% Chrom und den weiteren Legierungselementen Molybdaen, Vanadium, Niob und z.T. Wolfram wurde der Einfluss von Temperatur und Dauer des Anlassens auf Haerte und Gefuege untersucht. Nach dem Austenitisieren und folgender Luftabkuehlung wurden die Staehle bei Temperaturen unter, bei und ueber Ac1b unterschiedliche Zeiten angelassen und einer Haertepruefung unterzogen. Anhand der Haerte wurden Anlassschaubilder erstellt und der Hollomon-Jaffe-Parameter an den drei Staehlen innerhalb seiner Anwendungsgrenzen bestimmt. Gefuegebilder (REM) belegen die Ausbildung der Karbide und des Martensits. Bei Anlasstemperaturen unterhalb Ac1b tritt ein Haerteabfall auf, bei Temperaturen oberhalb Ac1b kommt es infolge der dabei stattfindenden Teilaustenitisierung zu einem Haerteanstieg. Beim Anlassen unterhalb Ac1b nimmt die Anlassbestaendigkeit in der Reihenfolge P 91, NF 616, E 911 zu. (orig.)
[en] Carbide-reinforced Ti2AlNb matrix composites were spark plasma sintered at 1100 °C by incorporating CNTs into single-B2-phase Ti-22Al-25Nb powders. The as-SPSed alloys were solution treated and then aged in different phase regions. By kinetics analysis and energy-dispersive spectroscopy, it is found carbon will stabilize α2 phase during solution treatment, and the formation of carbide results in the Nb-depleted regions, which further induces the formation of curly B2 + O Widmanstätten structure during quenching. Different from the general Widmanstätten structure in the aged Ti2AlNb alloy, the remained α2 will consume the B2 within the Widmanstätten structure, when the carbon-added alloy is aged in B2 + O phase region. Compared to the alloy without CNTs, the Vickers hardness of the aged carbon-added Ti2AlNb alloy is increased significantly, which is related to the uniform and abundant columnar carbides within the O-phase matrix.
[en] Plastic strain distribution around spherical indentations in annealed polycrystalline copper has been determined by Vickers microhardness mapping of carefully prepared median plane sections through the indentations and comparing the microhardness values with those of small cylinders of the annealed copper which had been uniaxially compressed to different plastic natural strains (i.e. true strains, defined as ln(l0/l)) in the range of 0.01 to 0.97. The spherical indentations were of dimensionless size a/R in the range of 0.08 to 0.85, where a and R are the radii of contact and indenter, respectively. It is shown that the magnitude of the equivalent maximum plastic natural strain εmax increases nonlinearly with increasing a/R and reaches a value of 0.72 for an indentation of a/R = 0.85. The measured values of the εmax are considerably higher than the 'representative' strain εr values predicted by the empirical formula εr = 0.2a/R. The implications of these findings have been discussed in relation to determining the uniaxial flow stress versus strain curve of a power-law hardening solid using the spherical indentation test. (orig.)
[en] This paper reports on the fracture toughness of a sintered dense α-SIC estimated by the Vickers indentation microfracture method in the low-load Palmqvist crack regime. It was observed that the use of simultaneously Vickers hardnesses does not yield reliable fracture toughness values, nor does application of the median-crack -derived equation. It is necessary to utilize a load-independent, crack-free hardness value with this toughness estimation method
[en] To study the effects of zirconium (Zr) addition on the microstructure, hardness and the tensile properties of oxide dispersion strengthened (ODS) ferritic-martensitic steels, two kinds of 9Cr-ODS ferritic-martensitic steels with nominal compositions (wt.%) of Fe-9Cr-2W-0.3Y_2O-3 and Fe-9Cr-2W-0.3Zr-0.3Y_2O_3 were fabricated by the mechanical alloying (MA) of premixed powders and then consolidated by hot isostatic pressing (HIP) techniques. The experimental results showed that the average grain size decreases with Zr addition. The trigonal δ-phase Y_4Zr_3O_1_2 oxides and body-centered cubic Y_2O_3 oxides are formed in the 9Cr-Zr-ODS steel and 9Cr non-Zr ODS steel, respectively, and the average size of Y_4Zr_3O_1_2 particles is much smaller than that of Y_2O_3. The dispersion morphology of the oxide particles in 9Cr-Zr-ODS steel is significantly improved and the number density is 1.1 x 10"2"3/m"3 with Zr addition. The 9Cr-Zr-ODS steel shows much higher tensile ductility, ultimate tensile strength and Vickers hardness at the same time
[en] We analyzed acoustic emission signals obtained from three kinds of brittle materials under compression load by Vickers hardness tester. The results obtained can be summarized as follows; The signal in each material could be divided into three signal based on the properties of load. All specimens were not detected acoustic emission signals in stage II which was load constant region, and were detected in stage I and stage III. Glass was detected high amplitude signals in stage III. AI2O3 and Al2O3/SiC were detected high amplitude signals in stage I
[en] Twelve steel works laboratories took part in the experimental programme carried out on the systematic study of the hardness-strength relationship for very diverse ranges of steels. The Rm strength regressions were calculated in terms of the Brinell and Vickers hardness numbers
[fr]Douze laboratoires d'usines siderurgiques ont participe au programme experimental entrepris sur l'etude systematique de la relation durete-resistance pour des gammes d'aciers tres divers. Les regressions des resistances Rm ont ete calculees en fonction des duretes de Brinell et Vickers