Pushing and pulling for high strength: High-strength aluminum alloys are important for producing lightweight cars, trains, and airplanes. The traditional strategy for doing this is through hours of high-temperature cycling to form precipitates in the alloy. Sun et al. developed a processing method that relies on mechanical cycling by pushing and pulling on the alloys at room temperature. This quickly creates many very fine precipitates that have the same strengthening effect as those characteristic of traditional thermal methods. This method should also work for other alloy systems. Science , this issue p. 972

The fatigue performance of high strength aluminum alloys used in planes, trains, trucks and automobiles is notoriously poor. Engineers must design around this important limitation to use Al alloys for light-weighting of transportation structures. An alternative concept for microstructure design for improved fatigue strength is demonstrated in this work. Microstructures are designed to exploit the mechanical energy imparted during the initial cycles of fatigue to dynamically heal the inherent weak points in the microstructure. The fatigue life of the highest strength Aluminum alloys is improved by 25x, and the fatigue strength is raised to ~1/2 the tensile strength. The approach embraces the difference between static and dynamic loading and represents a conceptual change in microstructural design for fatigue.

The temporal evolution of microhardness and Al₃(Er,Zr/Hf) precipitates are investigated in Al-Er-Zr/Hf alloys during annealing at 450 °C and 500 °C. The microhardness of the alloys decreases continuously with the prolonged annealing time due to the coarsening of the precipitates. Different weakening amplitudes are observed because of the disparity of the precipitate coarsening rate that is related to the disparity in their intrinsic diffusivities of Er, Zr, and Hf solute atoms in an Al matrix. The addition of Hf element is beneficial to enhancing the coarsening resistance, thus improving the thermal stability of the alloys. Introducing such elements to improve the thermal stability of precipitates can provide a new idea or choice for the development of heat-resistant aluminum alloys.

Ti/TiN multilayer films were synthesized on 17-4PH stainless steel using unbalanced magnetron sputtering. The modulation periods is ranged from 100nm to 350 nm. The microstructure of the multilayer films was analyzed by X-ray diffraction. The cross-section views of the multilayer films were studied by scanning electron microscope (SEM). The microhardness and wear resistance of the films were measured by a HXD-1000 microhardness tester and ball-on-disk wear tester. The corrosion resistance of the multilayer films was evaluated by potentiodynamic polarization scans in a 3% NaCl solution. The results showed that there was TiNx intergradation layer in the films. The microhardness and the wear resistance of the multilayer films increased with the layer number. The Ti/TiN multilayer can improve the corrosive resistance of the 17-4PH stainless steel.