The process of martensitic α′( α″) phase decomposition in titanium alloys has not been sufficiently characterised in the literature – especially in terms of plastically deformed martensite. The research results of water-quenched Ti–6Al–4V alloy, subsequently cold deformed in compression test and tempered at the temperature range of 600–900°C for 1 and 2 h were presented in the paper. Light and scanning electron microscopy observations revealed the influence of plastic deformation on tempered martensite laths morphology – particularly at the temperature of 900°C – it favoured their fragmentation and spheroidisation. The effect of plastic deformation on characteristic temperatures of α′( α″)→ α +  β phase transformation, phase composition and alloying elements distribution in phase constituents of Ti–6Al–4V alloy was identified and evaluated too. This paper is part of a thematic issue on Titanium. GRAPHICAL ABSTRACT

The aim of this work was to establish the influence of the thickness of the anodic coatings on their mechanical properties and to understand the relation between their hardness and the abrasion resistance. The coatings were produced in the hard anodizing process onto the 6061-T6 aluminum alloy. Their thickness was in the range between 19 and 43 lm. The abrasion resistance was determined by using Taber abrasion test. The weight losses of the coatings obtained were in the range between 15 and 11 mg and decreased with their increasing thickness. It has been shown that the hardness measured on the cross sections of the coatings did not correspond to their abrasion resistance. Thus, the new approach has been proposed. The hardness of the coatings was estimated on the basis of the results of the scratch test performed at the constant load. The results obtained correspond to the abrasion resistance of the coatings.

A 0.5 µm thick layer of rhodium was deposited on the CMSX 4 superalloy by the electroplating method. The rhodium-coated superalloy was hafnized and aluminized or only aluminized using the Chemical vapour deposition method. A comparison was made of the microstructure, phase composition, and oxidation resistance of three aluminide coatings: nonmodified (a), rhodium-modified (b), and rhodium-and hafnium-modified (c). All three coatings consisted of two layers: the additive layer and the interdiffusion layer. Rhodium-doped (rhodiumand hafnium-doped) β-NiAl phase was found in the additive layer of the rhodium-modified (rhodium-and hafnium-modified) aluminide coating. Topologically Closed-Pack (µ and σ) phases precipitated in the matrix of the interdiffusion layer. Rhodium also dissolved in the β-NiAl phase between the additive and interdiffusion layers, whereas Hf-rich particles precipitated in the (Ni,Rh)Al phase at the additive/interdiffusion layer interface in the rhodium-and hafnium-modified coating (c). The rhodium-modified aluminide coating (b) has better oxidation resistance than the nonmodified one (a), whereas the rhodium-and hafnium-modified aluminide coating (c) has better oxidation resistance than the rhodium-modified (b) and nonmodified (a) ones.

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The influence of long term annealing on microstructure of Al-Cu4-Ni2-Mg aluminum alloy was investigated. The castings were subjected to T6 heat treatment followed by annealing at 523 K and 623 K for 100, 150, 300, 500 and 750 hours. The soaking time and temperature was adjusted by corresponding to real service conditions of the elements of an aircraft and motor engines from investigated alloys. Microstructural examination of the alloy was carried out with optical microscope, as well as scaning and transmissiom electron microscopes. The result of microscopic analysis showed that applied heat treatment caused an increasing in the particles of hardening (θ’-Al2Cu) phase size. The significant growth of the length and changing the value of shape factor of hardening phase precipitations was observed. The phenomenon of the increase in size and change in shape of precipitations of hardening phases continually change with the prolonged holding time at high temperature. The microstructure degradation is connected to a decrease of mechanical properties of alloy, confirmed by the result of tensile tests.