In the present investigation, the microstructural characterisation of the AZ91 Mg alloy produced by spark plasma sintering (SPS), as well as the evaluation of its hot compression behaviour, has been performed. Based on the differential scanning calorimetry analyses of the starting powders, three SPS cycles are investigated, using temperatures of 400 and 450°C, and at 450°C with previous solubilisation soaking at 420°C. Despite different microstructural and hardness characteristics, the three alloys display similar hot compression behaviour. At 200°C, the formation of an unstable crack, which propagates at 45° with respect to the loading axis, is observed after the occurrence of the peak load. At higher testing temperatures, after reaching the peak stress, the flow stress decreases slowly with increased strain of ∼0·51. Such behaviour corresponds with the observation of an accelerated cracking due to the propagation of decohesions at the interparticle regions. Ultimately, SPS allowed for attainment of high relative density; however, the sintering degree of the materials was quite low.

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Ultra-low-temperature process treatments could raise tool steel wear resistance through microstructural change that occurs on the material, enhancing, that way, tools and dies lifetime. To investigate the tool steel wear resistance impact, micro-abrasive wear tests were carried out and an analysis based on the Archard's law was considered, evaluating specimen mass loss by laser interferometry. Micro-hardness, X-ray diffractometry, scanning and optical microscopy and carbides quantitative evaluation were carried out aiming to material characterisation. Results demonstrated a micro-hardness improvement, ranging from 0.9–4.7% for the cryogenically treated specimens, when compared to the bulk material. This effect is related, mainly, to the retained austenite transformation and to the increase of fine secondary carbides dispersed amount in the martensitic matrixes cryogenically treated.

Duplex stainless steels (DSS) are alloys with binary microstructure consisting of ferrite (δ) and austenite (γ), combining high mechanical properties and corrosion resistance by pitting and stress corrosion, due to the two phases austenite/ferrite. However, the formation of secondary and intermetallic phases, during solidification processes, heat treatment or welding in duplex steels tend to cause the degradation of its main properties. The present study aim to investigate the corrosion behaviour of UNS S82441 aged at 850°C for 30, 300 and 3000 minutes, due to the formation of sigma phase. Corrosion resistance evaluation was performed by means of stress corrosion testing, potenciodinamic polarization and mass loss. The microstructural characterization and morphology confirmed the presence of sigma phase in the UNS S82441 duplex stainless steel, and that the amount of this phase increases with the time of heat treatment of aging. The aging time influences negatively the corrosion resistance of this steel, with a gradual drop of up to 50% on passivation regime for the condition of aging at 850°C for 3000 minutes.

The influence of the microstructure on the wear behaviour of some hardened sintered steels produced with diffusion bonded powders and subjected to through hardening, carburising and sinterhardening was investigated. In dry sliding, wear was oxidative in nature and the localised surface deformation caused delamination, which further reduce the wear resistance. In these conditions, the harder the microstructure, the better the resistance to plastic strain. In lubricated rolling-sliding, wear occurs by rolling contact fatigue. Cracks nucleation was caused by the stress localisation at the pores edges. In this case, a brittle virgin martensite has a negative effect. Tempering reduces martensite brittleness, and makes its resistance to nucleation and propagation of the rolling contact fatigue comparable to that of Fe-Ni austenite.

Factors influencing effectiveness of automated comparisons, test-fired bullets, and cartridge cases from 0.38 Special revolvers were logged into the Evofinder Ballistic ID System. Tests were performed as follows: First test correlated test-fires of the same type, second test compared different types of ammunition components, third test replicated the second test in a larger database, and fourth test replicated the third test with students having no previous firearm identification experience. System effectiveness with projectiles in the first test was 0.89. With cartridge cases, effectiveness was 0.79 with combined results, but analysis of separate results by breech face and firing pin revealed low effectiveness by breech face (0.40). In the second, third, and fourth tests, effectiveness with projectiles were 0.61, 0.51, and 0.44. In addition, these tests had effectiveness with cartridge cases equivalent to 0.55, 0.43, and 0.44. Results are useful to establish routine protocols, system improvements, or comparative assessment of other electronic systems.

Production and processing of titanium alloys are expensive and its alloys show low wear resistance. Substrates of Ti-40Zr, used for orthopedic implants, were obtained from the elemental mixture of hydrogenated powders, followed by a sequence of cold uniaxial and isostatic pressing and vacuum sintering. Aiming wear resistance increase, samples were coated by physical vapor deposition using electron beam technique (EB-PVD). Multilayer coatings with three different configurations were undertaken: Ti/TiN, Ti/TiN/ZrN and Ti/TiN/ZrN/TiN. Micro-abrasive wear tests were conducted by ball-cratering, with abrasive slurry of silicon carbide (SiC). The wear craters were measured at intervals corresponding to increments in the sliding distance of approximately 14 m. Range of the normal force were between 0.35 and 0,45 N. Scanning electron microscopy was used to evaluate the wear crater and the wear mode. All experiments showed three-body abrasive wear and a reduction of one order of magnitude in wear coefficient for two coated samples: 2,58∙10-12m³(Nm)-1to substrate, 5,4∙10-13m³(Nm)-1to Ti+TiN film and 7,22∙10-13m³(Nm)-1to Ti+TiN+ZrN film. In the Ti+TiN+ZrN+TiN experiment the wear coefficient of film is nearer to the substrate, 7,58∙10-13m³(Nm)-1. The multi-layers containing ZrN presented wear coefficient higher than Ti/TiN films, possibly due to existing residual stresses.