The high-temperature stability and mechanical properties of refractory molybdenum alloys are highly desirable for a wide range of critical applications. However, a long-standing problem for these alloys is that they suffer from low ductility and limited formability. Here we report a nanostructuring strategy that achieves Mo alloys with yield strength over 800 MPa and tensile elongation as large as ~ 40% at room temperature. The processing route involves a molecular-level liquid-liquid mixing/doping technique that leads to an optimal microstructure of submicrometre grains with nanometric oxide particles uniformly distributed in the grain interior. Our approach can be readily adapted to large-scale industrial production of ductile Mo alloys that can be extensively processed and shaped at low temperatures. The architecture engineered into such multicomponent alloys offers a general pathway for manufacturing dispersion-strengthened materials with both high strength and ductility.

Commercially aged aluminum alloys commonly contain second-phase particles of three class sizes, and all contribute appreciably to the mechanical properties observed at the macroscopic scale. In this article, a multiscale model was constructed to describe the individual and coupling influences of the three types of second-phase particles on tensile ductility. The nonlinear relationships between the parameters of particles, including volume fraction, size, aspect ratio, shape, and ductility, were then quantitatively established and experimentally validated by the measured results from disc-shaped precipitate containing Al-Cu-Mg alloys and needle-shaped precipitate containing Al-Mg-Si alloys, as well as by using other researchers' previously published results. In addition, we discuss extending this model to predict the fracture toughness of aluminum alloys.

It is generally accepted that deformation twinning in coarse-grained metals contributes the macroscopic strain, while most deformation twins in nanocrystalline (NC)metals, contrary to popular belief, yield zero net macroscopic strain via either the cooperative or random activation of all three Shockley partials. In the former, the three partials with a particular (b 2 :b 1 :b 3 ) triplet unit are successively emitted, while in the latter the three partials are randomly activated in equal numbers. Here we report that there exists a transition between the two zero-strain deformation twinning mechanisms, i.e., from cooperative activation of partials to random activation of partials in NC Cu with medium stacking-fault energy, that occurs with decreasing grain size at room temperature and different strain rates. This experimental finding provides insight into the understanding of deformation twinning.