Solid State Phenomena Vol. 212

Abstract: The effect of carbon additions on the microstructure and properties of unalloyed titanium with 0.2 and 0.5 wt. % C has been studied. Carbon has been found to appear as TiC carbide in these alloys. Its presence translates into increase in allotropic transformation temperature as well as hardness and strength properties of alloys at the expense of reduction in its ductility. It has been demonstrated that these alloys can be subject to hot deformation, and with low carbon content also to cold deformation, and additionally strengthened by solution treatment.

Abstract: The paper presents the microstructure analyzing of composite with aluminium matrix containing porous Al₂O₃ preform. The AlSi12CuMgNi eutectic alloy have been modified by 1 wt% Mg and 0.03 wt% Sr additions. The magnesium to improve the wettability between matrix and ceramic reinforcement have been added. In turn 0.03 wt% strontium addition were used to changes the size and morphology of the Al-Si eutectic grains. The components and composite material obtained by the centrifugal infiltration process was characterized by means of light and scanning microscopy methods. The conducted investigations proved the large degree of infiltration of ceramic porous by the aluminium alloy and good connection in the boundary area.

Abstract: The article presents the results of tests connected with influence of strain parameters on the susceptibility to hot working of magnesium lithium alloys with lithium content of 7.5% mass. Plasticity tests were conducted in compression test from room temperature up to 400°C with strain rate of 0.1s^-1. Conducted tests allowed for determination of susceptibility of magnesium alloys with different lithium content to hot working. The results were compared with typical alloy AZ31. The results of influence of deformation temperature on the microstructure of tested alloys are also presented in this paper.

Abstract: The influence of prolonged ageing on the precipitation process of the secondary phases in an Fe-Ni superalloy of A-286 type has been studied. The samples were subjected to a solution heat treatment at 980°C for 2 h and water quenched, and then aged at temperatures of 715, 750 and 780°C at holding times from 0.5 to 500 h. Structural investigations were conducted using TEM and X-ray diffraction methods. The X-ray phase analyses performed on the isolates were obtained by anodic dissolution of the solid samples. After solution heat treatment the alloy has the structure of twinned austenite with a small amount of undissolved precipitates, such as carbide TiC, carbonitride TiC_0.3N_0.7, nitride TiN_0.3, carbosulfide Ti₄C₂S₂, Laves phase Ni₂Si, and boride MoB. The application of ageing causes precipitation processes of γ-Ni₃(Al,Ti), G (Ni₁₆Ti₆Si₇), η (Ni₃Ti), β (NiTi) and σ (Cr_0.46Mo_0.40Si_0.14) intermetallic phases, as well as the carbide M₂₃C₆. It was found that the main phase precipitating during alloy ageing was the γ intermetallic phase.

Abstract: The work concerns a new group of titanium alloys with properties improved due to the presence of carbon. Investigated alloys were melted in a vacuum induction furnaces with copper water cooled crucibles. It was showed the influence of the solution temperature in range of 875 to 975oC on the number, size and distribution of carbides in pure titanium with content of 0.2 wt.% carbon and on the hardness test of researched alloys. The observed changes in the microstructure and properties are the result of phase transformations taking place during heating: α + TiC α α + β β + TiC.

Abstract: The detailed microstructural analysis of HCM12 steel after long time (100 000 hours) exposure at service temperatures around 600°C was investigated by means of scanning transmission electron microscopy. The results show, that the recovery processes of the martensite lath structure and δ ferrite are significantly different. Moreover are differences in particles precipitating at the martensite and δ ferrite. The intensive process intragranular M₂₃C₆ and Laves particles precipitating is observed at the martensite/ δ ferrite interfaces.

Abstract: In this article, characteristics of the macro- and microstructure of cast Ti-47Al-2W-0.5Si intermetallic alloy were determined. The abilities to shape unfavorable parameters of this structure, i.e. large grain and high content of columnar grains, by using crystalline boron modifier were presented. The effect of modification process on selected alloy properties was shown. The content of modifier at which structural changes are highest as well as the form in which it exists after modification were determined.

Abstract: The effect of heat treatment on the structure and hardness of the ZnAl22Cu3 alloy is presented in the paper. ZnAl22 and ZnAl22Cu3 alloys were tested. The scope of the examination included dilatometry, structural and hardness tests. Very interesting is the effect of the transformation, occurring at lower temperatures on the structure and hardness of the alloy. There are found, that soaking at 185°C causes a decrease in the hardness of the ZnAl22Cu3 alloy. Observed ZnAl22Cu3 alloy hardness decrease is related to the disappearance of zinc-rich dendrites and the transition of zinc to a eutectoid mixture.

Abstract: The paper presents results of the investigation of SM5Ti3Nb2 steel carbide isolates. The acids and acid mixtures for dissolution of selected carbides phase isolates, using microwave technique were specified. This way of dissolution of carbide isolates reduced the time of mineralization to about 10-15 minutes. Presented methods of dissolution can be applied in the chemical analysis of carbide isolates, using atomic absorption spectrometry and optical emission spectrometry inductively coupled plasma. It is indicated the acids, using to removal of noncarbide metallic residue in isolates.