Effect of Microstructure on the Corrosion Resistance of the AE42 Magnesium Alloy Processed by Rotary Swaging

Microstructure and corrosion resistance of the AE42 commercial alloy processed by extrusion and rotary swaging were investigated. Microstructure characterization showed an increasing volume fraction of the refined grains with increasing stage of swaging processing. However, their presence was limited solely to the peripheral ring of ≈1 mm in all studied conditions of swaged material. Corrosion resistance investigation showed continuous decrease of polarization resistance that was attributed to the grain refinement and insufficient homogenization of the alloying elements during the swaging process

The Very High Cycle Fatigue Behaviour of Ti-6Al-4V Alloy

The high cycle and very high cycle fatigue properties of the titanium alloy Ti-6Al-4V with a duplex microstructure were investigated at room temperature. High cycle fatigue tests were performed in the range from 10⁴ to 10⁷ cycles by rotating bending at the frequency of 30 Hz. The very high cycle fatigue tests were carried out in the range from 10⁷ to 10¹⁰ cycles in tension-compression on an ultrasonic fatigue testing machine at the frequency of 20 kHz. The stress amplitude was found to decrease with increasing number of cycles in the whole range from 10⁴ up to 10⁹ cycles and only at the highest number of cycles $(N_{F}=10^9)$ the alloy exhibits the fatigue limit of 460 MPa. The detail fractographic analysis was performed to characterize the fatigue failure mechanisms. Both subsurface and surface crack initiation were observed in very high cycle fatigue region. No inclusions, but only local chemical inhomogeneity in microstructure was observed at the locations of subsurface fatigue crack initiation in alpha-grains

Odporność na powierzchniowe zużycie zmęczeniowe żeliwa ADI poddanego kulowaniu

Compared to other ferrous materials, austempered ductile iron (ADI) has marked economic advantages such as low melting temperature, low shrinkage, excellent castability, good machinability, and high damping capacity. This makes it a potential candidate material for automotive components. The desired bulk properties required by these components can be obtained through careful control of the austempering parameters. However, to truly unlock its full potential, surface engineering techniques are necessary to improve the surface properties and characteristics of this material. This study provides an insight on the tribological behaviour of shot peened ADI. Lubricated rolling contact fatigue tests revealed that shot peening resulted in a 72% decrease in the average contact fatigue life when compared to the resulting fatigue life obtained by the as-austempered ADI specimens.W porównaniu ze stalą i staliwem żeliwo ADI cechuje się korzystniejszymi cechami użytkowymi, takimi jak niska temperatura topnienia, niewielki skurcz odlewniczy, doskonała lejność, dobra obrabialność i wysoka zdolność do tłumienia drgań. Cechy te czynią żeliwo ADI potencjalnym materiałem do zastosowania w przemyśle motoryzacyjnym. Parametry materiałowe wymagane dla tych elementów maszyn mogą być uzyskane jedynie w wyniku prawidłowego przeprowadzenia procesów obróbki cieplnej skutkujących wytworzeniem struktury ausferrytycznej. Jednakże, by żeliwo to mogło być stosowane, niezbędna jest także poprawa właściwości użytkowych warstwy wierzchniej. W artykule zaprezentowano wyniki badań tribologicznych śrutowanego żeliwa ADI. Testy powierzchniowego zużycia zmęczeniowego wskazały na zmniejszenie o 72%, średniej trwałości żeliwa ADI po kulowaniu w stosunku do tegoż żeliwa w stanie wyjściowym

Estimation of Dislocation Density in Cold-Rolled Commercially Pure Titanium by Using Synchrotron Diffraction

Cold rolling (CR) leads to a heavy changes in the crystallographic texture and microstructure, especially crystal defects, such as dislocations, and stacking faults increase. The microstructure evolution in commercially pure titanium (cp-Ti) deformed by CR at the room temperature was determined by using the synchrotron peak profile analysis of full width at half maximum (FWHM). The computer program ANIZC has been used for the calculation of diffraction contrast factors of dislocations in elastically anisotropic hexagonal crystals. The dislocation density has a minimum value at 40 pct reduction. The increase of the dislocation density at higher deformation levels is caused by the nucleation of new generation of dislocations from the crystallite grain boundaries. The high-cycle fatigue strength (HCF) has a maximum value at 80 pct reduction and it has a minimum value at 40 pct reduction in the commercially pure titanium