S.K. Shaha

Dislocation slip distance during compression of Al–Si–Cu–Mg alloy with additions of Ti–Zr–V

Abstract The plastic deformation behaviour of the Al–Si–Cu–Mg alloy with micro-additions of Zr–V–Ti was measured in the temperature range of 298–673 K and the true stress–true strain compression curves were used to calculate the dislocation slip distance (DSD). A new constitutive equation for the temperature dependent DSD was developed, based on Mott’s theory of strain hardening. The DSD predicted by the model was in good agreement not only with values achieved for the Al–Si–Cu–Mg alloy tested but also for other Al based and Pb–Sb alloys with deformation data available in the literature. A comparison of deformation and microstructure suggests that the grain refinement during hot compression deformation occurring due to continuous dynamic recrystallisation is responsible for a drastic growth of the DSD.

Aging characteristics of the Al-Si-Cu-Mg cast alloy modified with transition metals Zr, V and Ti

The hypoeutectic Al-7Si-1Cu-0.5Mg base alloy was modified with different contents of Zr, V and Ti. The wedge-shape samples with varying solidification rates during casting were subjected to isochronal aging at temperatures up to 500 °C. Moreover, as-cast and solution treated alloys were subjected to long-term isothermal aging at 150°C. As a reference, the A380 alloy, seen as commercial standard for the automotive application target, was used. The modified alloys exerted different aging characteristics than the A380 grade with higher peak hardness and lower temperature of alloy softening. Besides, the influence of the applied solidification rates on hardness after aging was less pronounced in modified alloys than in the A380 grade. For three combinations of Zr, V and Ti tested with contents of individual elements ranging from 0.14 to 0.47%, no essential differences in aging characteristics were recorded. The results are discussed in terms of the role of chemistry and heat treatment in generating precipitates contributing to the thermal stability of Al based alloys.

Effect of Transition Metals on Thermal Stability of Al‒Si Cast Alloys

Micro-additions of the transition metals Ti, Zr and V were explored to improve thermal stability of the cast hypoeutectic Al‒7Si‒1Cu‒0.5Mg (wt%) alloy. During high temperature exposures, the Cu- and Mg-rich phases along with the eutectic Si dissolved in the temperature range from 300 to 500 °C whereas the (AlSi)x(TiVZr) phases, containing transition metals, were present until alloy melting. Micro‒additions of Ti, V and Zr increased the alloy strength during testing under both static and cyclic loads. Improvements in the tensile and compressive strength as compared to the reference alloy were observed up to temperatures over 200 °C with more positive effect seen for the T6 state.

Low Cycle Fatigue of Aluminum‐Silicon Alloys for Power‐Train Applications

Vehicle lightweighting via the use of aluminum alloys is considered as one of the most important methods to meet stringent fuel-efficiency regulations and reduce CO2 emissions. Design of aluminum components requires strain-controlled low-cycle fatigue (LCF) behavior. This study was aimed at evaluating cyclic deformation characteristics and LCF life of an Al-7Si-1Cu-0.5Mg (wt.%) as a base alloy and the alloys with different additions of V, Zr and Ti elements in a T6 heat-treated condition. The base alloy contained typical phases of aluminum matrix, eutectic silicon, Mg-rich and Fe-rich particles. A small amount of Zr and V additions led to a complex microstructure. Increasing the amount of Zr, V and Ti resulted in the presence of a ductile type of Zr-V-Ti-rich particles. This effectively improved the ductility, ultimate tensile strength and fatigue life of this alloy, despite a slightly lower yield strength. Characteristic fatigue striations were observed to be presented not only in the aluminum matrix, but also in the Zr-V-Ti-rich particles.