High-temperature deformation of 6061 Al

The Effects of Iron-Bearing Intermetallics on the Fitness-for-Service Performance of a Rare-Earth-Modified A356 Alloy for Next Generation Automotive Powertrains

Aimed at improving the tensile strength and creep resistance of a rare earth-modified A356 alloy, this study adjusted the Mg and Mn concentration in the alloy, specifically aiming to transform the harmful Al5FeSi and Al9FeSi3Mg5 phase into Al15(Fe,Mn)3Si2. It was found that lowering the Mg concentration from 0.49 to 0.25 wt.% and raising the Mn concentration from 0.10 to 0.41 wt.% resulted in a near complete transformation of the Fe-bearing phases. This transformation led to a greater total volume fraction of Fe-intermetallics (2.9 to 4.1%), without affecting the volume fraction of the desirable, temperature-resistant, AlSiRE phase. Moreover, the chemistry modification led to a shift in the morphology of the AlSiRE phase while reducing its size. Combined with the decreased volume fraction of the harmful Fe precipitates, the chemistry modification improved the yield strength (YS), ultimate tensile strength (UTS) and modulus of elasticity by ~14%, 9%, and 10%, respectively. In addition, the steady-state creep rates of the high Mn alloy were lower at all stresses as compared to the low Mn alloy and the fracture stress was ~15 MPa higher, reaching 100% of the alloy’s original 250 °C YS.

Microscopic analysis of metal matrix composites containing carbon Nanomaterials

Metallic matrix composites reinforced with carbon nanomaterials continue to attract interest because of their excellent mechanical, thermal, and electrical properties. However, two critical issues have limited their commercialization. Uniform distribution of carbon nanomaterials in metallic matrices is difficult, and the interfaces between the nanomaterials and matrices are weak. Microscope-based analysis was recently used to quantitatively examine these microstructural features and investigate their contributions to the composites’ mechanical, thermal, and electrical properties. The impacts of the microstructure on these properties are discussed in the first section of this review. In the second section, the various microscopic techniques used to study the distribution of carbon nanomaterials in metallic matrices and their interfaces are described.