No abstract

No abstract

The effects of temperature and testing procedure on the wetting properties of molten Al on polycrystalline TiO 2 substrates were studied by a sessile drop method in vacuum at 1173-1373 K. For the common contact heating procedure, oxidized molten Al wets titania at T > 1210 K. The removal of the oxide film from the Al drop by means of a capillary purification procedure makes the Al/TiO 2 couple wettable at 1173 K. The structure and chemistry characterization of Al/TiO 2 interfaces shows that molten Al reacts with TiO 2 to form fine alumina particles and Ti, which subsequently is dissolved in the Al drop. However, this reaction is remarkable at 1373 K only and much higher temperatures are required for successful reactive synthesis of Al/Al 2 O 3 composites.

The aim of the present work was to determine the influence of the retrogression and reaging (RRA) heat treatment on the correlation between microstructure, mechanical properties and susceptibility to stress corrosion cracking (SCC) of the AlZn5Mg1 alloy in dry air and sea water. The alloy received in the T6 temper was subjected to 9 different heat treatments, including retrogression at temperature 453 -513 K for 600 -3600 s, and reaging at temperature 363 K or 403 K for 16 h, 24 h or 48 h. The susceptibility to SCC was investigated by slow strain rate tensile tests at 10 À6 s À1 strain rate; change in time to failure, fracture energy and reduction in area were taken into account. Generally, the heat treatment improving mechanical properties increased susceptibility to SCC. The observed effects were discussed in terms of change in microstructure, especially size and distribution of phase precipitates. The role of change in dislocation network was the most likely of no importance.

In this paper, the effect of applied multi-variant heat treatment on microstructure, phase composition and mechanical response of Haynes 282 nickel-based superalloy was investigated. For this reason, temperatures of both stages of standard two-stage aging treatment (i.e., 1010°C/2 h + 780°C/8 h) were extended to 900-1100°C/2 h and 680-880°C/8 h ranges, respectively. Consequently, 30 different variants of heat treatment were applied. The microstructural features of heat-treated samples were investigated by means of light microscopy and SEM/EDS methods, while mechanical properties were examined via microhardness measurements. It was found that by using various combinations of temperatures of the first and second stage of aging, the room temperature hardness of Haynes 282 alloy can be decreased by 100 HV units or increased by up to 25 HV units as compared to that of the alloy subjected to the standard heat treatment schedule. The mechanical response of the alloy is determined by a complex structural evolution involving the secondary precipitation of c¢, M 23 C 6 and M 6 C phases, as well as their interaction with the fcc c matrix.

In the present work the evolution of the morphology (examined by means of SEM ) and changes in the chemical composition (examined by means of EDS microanalysis) of the intermetallic phases precipitates, containing Fe and Mn, in AA3004 type alloy, slowly cooled and frozen at 580, 510 and 430 °C, was analysed. The morphology of the intermetallic phase particles, depending on their chemical composition and precipitation temperature, was determined. It has been stated that intermetallic phases Al 6FeMn and a-Al(FeMn)Si, of different stoichiometry, precipitate at successive stages of solidification and cooling. The a-Al(FeMn)Si phase particles chinese script (Fe/Mn=2.3, [Fe+Mn]/Si=2.1-2.5) and branches (Fe/Mn=2.7-3.1, [Fe+Mn]/Si=2.3) were observed.

No abstract

The aim of the study was to design and optimize the complex, two-step heat treatment of Cu-Ni (Mn, Mo) ductile iron. A method for the formation and investigation of austempered ductile iron (ADI) by means of complex two-step and as comparative, standard one-step heat treatments has been developed, using quenching dilatometer. Investigations of proceeding phase transformations using differential dilatometric and DSC analysis supported by microstructural observations, hardness and austenite volume measurements have been carried out. An analysis of the temperature sequence of the ausferrite decomposition in the one-step and two-step ADI was performed, which allowed for the separation and identification of the effects responsible for the carbon-enriched austenite decomposition. A quantitative relationship was established between basic dimensional effects revealed on the differential dilatometric curve of ausferrite decomposition, which enables prognosis and optimization of the parameters of complex ADI heat treatment variants. Verification tests were performed on a stand equipped with salt furnaces enabling a quick transfer of samples from one bath to another without changing their initial temperature. Optimization of the two-step ADI heat treatment with the use of quantitative dilatometric analysis of the ausferrite decomposition, allowed to obtain for the temperature step-down heat treatment 390°C/15, 20 min ) 270°C/130 min the excellent mechanical properties, unattainable by means of standard 1-step ADI heat treatment.