Ambient-temperature time-dependent deformation of cast and additive manufactured Al-Cu-Mg-Ag-TiB2 (A205)

A dual-stage indentation test at ambient temperature including a constant indentation load rate followed by a constant indentation load-hold segment was employed to assess the time-dependent plastic deformation of cast and additive manufactured Al-Cu-Mg-Ag-TiB2 alloys in as-fabricated and T7 conditions at room temperature. Optical microscopy, scanning electron microscopy, electron backscattered diffraction, and transmission electron microscopy techniques were used to study the microstructure of the samples and to correlate the microstructure with the creep properties. That is, the indentation load/displacement/time data from depth-sensing indentation creep were combined with the advanced microstructural assessments to analyze the controlling mechanisms of creep in as-cast, as-built, and T7 samples. Expectedly, the microstructure of samples manufactured by different methods was substantially different in terms of the grain size and the distribution of TiB2 particles. The theta'', theta' and omega phase were formed in all heat-treated samples; however, the density of omega phase was higher in the cast-T7 samples. Distinct microstructure and precipitation density resulted in different indentation-derived properties, both cast and AM samples at T7 condition showed enhanced creep resistance compared to their as-manufactured counterparts. The main controlling mechanism of creep deformation was found to be dislocation creep based on the indentation-derived creep stress exponent values.

Automated summary

A dual-stage indentation test was conducted to assess the time-dependent plastic deformation of cast and additive manufactured Al-Cu-Mg-Ag-TiB2 alloys. The microstructure of the samples and its correlation with creep properties were studied using different microscopy techniques. The results showed that the microstructure and precipitation density had a significant impact on the indentation-derived properties and the creep resistance. Dislocation creep was identified as the main controlling mechanism of creep deformation.