The effect of grain size on the elevated temperature yield strength of polycrystalline aluminum

Study on the Effects of the Composite Addition of Al-5Ti-0.8C and La on the Microstructure and High-Temperature Mechanical Properties of ZL205A Alloy

The effects of Al-5Ti-0.8C and the rare-earth element La on the microstructure and high-temperature mechanical properties of ZL205A alloy were investigated. We found that the grains of 0.1%La + 0.3%Al-5Ti-0.8C alloy were fine, the morphology of the as-cast Al₂Cu phase was fragmented, and the precipitated phase was fine after T5 treatment. In particular, the high-temperature mechanical properties of 0.1%La + 0.3%Al-5Ti-0.8C alloy were significantly improved above 250 °C. The reason for the increase in high-temperature plasticity was attributed to the Al-La phase and the TiC particles, which refined the grains and reduced the tendency for intergranular fracture at high temperatures. More importantly, the high-temperature strengthening mechanism of the Al-5Ti-0.8C master alloy compounded with La was a result of the TiC introduced by the Al-5Ti-0.8C alloy, and the Al₁₁La₃ formed by the addition of La refined the grains in the matrix, promoted the precipitation of the needle-like θ'(Al₂Cu) phase, reduced the size of the θ'(Al₂Cu) phase, decreased the PFZ (Precipitation Free Zone), and increased the θ'(Al₂Cu) phase number, hindering dislocation and grain boundary motion.

Modelling of Creep in Alloys Strengthened by Rod-Shaped Particles: Al-Cu-Mg Age-Hardenable Alloys

In recent years, a creep model that does not involve adjustable parameters has been successfully applied to coarse-grained aluminum. The main feature of this model is that it is fully predictable. On the other hand, in the case of age-hardenable alloys, any physically-based creep model should take into account the changes in the volume fraction, size and distribution of strengthening precipitates, and the effect of grain size. With this aim in view, in this paper, the original model previously applied to single phase-alloys has been modified to describe the effects of the grain size and of the consequences of the high-temperature exposure on the strengthening role of precipitates. To this end, phenomenological equations describing the coarsening phenomena and their dependence on the applied stress have been introduced. The modified model has given an excellent description of the experimental behavior of an AA2024-T3 alloy tested at 250 and 315 °C and has provided a sound explanation of the difference observed when comparing the minimum creep rate obtained using two different testing techniques.