The paper presents the results of tests concerning the effect of the extrusion process in the complex strain state on the microstructure and properties of one of magnesium alloy with aluminium, zinc and manganese, designated AZ61. Due to its specific gravity, it is increasingly being used in the automotive and aerospace industries to reduce the weight of structural elements. As a result of plastic deformation processes, rods with a diameter of 8, 6 and 4 mm were obtained from AZ61 magnesium alloy. The microstructure analysis was performed using light and electron microscopy (STEM) techniques in the initial state and after plastic deformation. Microstructure studies were supplemented with a quantitative analysis using the Metilo program. A number of stereological parameters were determined: average diameter of grain, shape factor. A static tensile test was carried out at 250ºC and 300ºC, at deformation rates of 0.01, 0.001 and 0.0001 m·s–1. Better plastic properties after deformation using KoBo method were obtained than with conventional extrusion.

The examined material comprised two grades of corrosion-resistant cast steel, namely GX2CrNiMoN25-6-3 and GX2CrNiMoCuN25-6-3-

3, used for example in elements of systems of wet flue gas desulphurisation in power industry. The operating conditions in media heated

up to 70°C and containing Cl- and SO4 ions and solid particles produce high erosive and corrosive wear.The work proposes an application

of the σ phase as a component of precipitation strengthening mechanism in order to increase the functional properties of the material.

The paper presents the results of examination of the kinetics of σ phase precipitation at a temperature of 800°C and at times ranging from

30 to 180 minutes. Changes in the morphology of precipitates of the σ phase were determined using the value of shape factor R.

Resistance to erosion-corrosion wear of duplex cast steel was correlated with the kinetics of sigma phase precipitating.

The paper presents the results of examination concerning optimization of the σ phase precipitates with respect to the functional properties of ferritic-austenitic cast steel. The examined material comprised two grades of corrosion-resistant cast steel, namely GX2CrNiMoN25-6-3 and GX2CrNiMoCuN25-6-3-3, used for example in elements of systems of wet flue gas desulphurisation in power industry. The operating conditions in media heated up to 70°C and containing Cl- and SO4 ions and solid particles produce high erosive and corrosive wear. The work proposes an application of the σ phase as a component of precipitation strengthening mechanism in order to increase the functional properties of the material. Morphology and quantities of σ phase precipitates were determined, as well as its influence on the erosion and corrosion wear resistance. It was shown that annealing at 800°C or 900°C significantly improves tribological properties as compared with the supersaturated state, and the best erosion and corrosion wear resistance achieved due to the ferrite decomposition δ → γ’ + σ was exhibited in the case of annealing at the temperature of 800°C for 3 hours.