Investigation of relaxation behavior in highly rejuvenated bulk metallic glasses by in-situ synchrotron X-ray scattering

Relaxation behaviors of highly rejuvenated Zr50Cu40Al10 bulk metallic glass was investigated using synchrotron X-ray scattering coupled with differential scanning calorimetry. The relaxation of rejuvenated volume is found to correspond to a marked exothermic event prior to the glass transition. High-energy synchrotron X-ray measurements of the structure factor show that annihilation of rejuvenated volume correspond to a sharpening of the scattering peaks. The calculated reduced pair distribution function suggests that the atomic re-arrangement in the second shell are largely responsible for the reduction in the free volume and decrease in full-width at half-maximum of the Total Structure Factor observed during structural relaxation. Mechanical properties in the highly rejuvenated metallic glass were evaluated as a function of annealing temperature

Unveiling the mechanism of phase and morphology selections during the devitrification of Al-Sm amorphous ribbon

The complex interplay between energetic and kinetic factors that governs the phase and morphology selections can originate at the earliest stage of crystallization in the amorphous parent phases. Because of the extreme difficulties in capturing the microscopic nucleation process, a detailed picture of how initial disordered structures affect the transformation pathway remains unclear. Here, we report the experimental observation of widely varying phase selection and grain size evolution during the devitrification of a homogeneous melt-spun glassy ribbon. Two different crystalline phases θ−Al5Sm and ɛ−Al60Sm11 are found to form in the different regions of the same metallic glass (MG) ribbon during the devitrification. The grain size of the ɛ−Al60Sm11 phase shows a strong spatial heterogeneity. The coarse-grained ɛ−Al60Sm11 phase coupled with the small volume fraction of the θ−Al5Sm phase is preferably formed close to the wheel side of the melt-spun ribbon. Combining experimental characterization and computational simulations, we show that phase selection and microstructure evolution can be traced back to different types and populations of atomic clusters that serve as precursors for the nucleation of different crystalline phases. Inhomogeneous cooling rates cause different structure orders across the glass sample during the quenching process. Our findings provide direct insight into the effect of structural order on the crystallization pathways during the devitrification of MG. It also opens an avenue to study the detailed nucleation process at the atomic level using the MG as a platform and suggests the opportunity of microstructure and property design via controlling the cooling process

Investigation of relaxation behavior in highly rejuvenated bulk metallic glasses by in-situ synchrotron X-ray scattering

Relaxation behaviors of highly rejuvenated Zr50Cu40Al10 bulk metallic glass was investigated using synchrotron X-ray scattering coupled with differential scanning calorimetry. The relaxation of rejuvenated volume is found to correspond to a marked exothermic event prior to the glass transition. High-energy synchrotron X-ray measurements of the structure factor show that annihilation of rejuvenated volume correspond to a sharpening of the scattering peaks. The calculated reduced pair distribution function suggests that the atomic re-arrangement in the second shell are largely responsible for the reduction in the free volume and decrease in full-width at half-maximum of the Total Structure Factor observed during structural relaxation. Mechanical properties in the highly rejuvenated metallic glass were evaluated as a function of annealing temperature.</p

Influence of Applied Load and Sliding Velocity on Tribocorrosion Behavior of 7075-T6 Aluminum Alloy

In this paper, the tribocorrosion behavior and synergistic effect of 7075-T6 aluminum alloy under different applied loads (100, 150, and 200 N) and sliding velocities (100, 150, and 200 rpm) were studied in a 3.5 wt.% NaCl solution. Tribocorrosion experiments were conducted in a tribobocorrosion system with pin-on-disc testing. The results show that the interaction between applied load and sliding velocity significantly affects the mechanical and electrochemical properties of 7075-T6 aluminum alloy. Increases in sliding velocity and applied load will accelerate the corrosion. Due to the synergistic effect of corrosion and wear, the wear rate is almost unchanged as the sliding velocity increases. When the applied load increased from 100 to 200 N, the wear rate increased from 1.97 × 10−5 to 2.08 × 10−5 mm3/N·m, and the delamination wear phenomenon was aggravated

Ultrasonic Additive Manufacturing of Metallic Materials

Ultrasonic additive manufacturing (UAM), a solid-state additive manufacturing technology, was invented in 1999 by Dawn White [...

The Effect of Ru on the Evolution of the γ′ Phase in Ni-Al-Ru Alloys

With the development and wide application of nickel-based single-crystal superalloys, the effect of Ru on the microstructure stability and high-temperature properties of superalloys is becoming increasingly important. In this study, the effect of Ru on the evolution of the γ′ phase in Ni-Al-Ru ternary alloys during aging treatment was analyzed, using a scanning electron microscope and transmission electron microscope, combined with energy-dispersive spectroscopy. The relationship between chemical partition behavior and γ/γ′ lattice misfit was investigated in detail. During the aging process, Ru addition suppressed the growth rate and rafting process of γ′ precipitates, while the effect of Ru on hindering γ′ phase growth was reduced when the Ru content was over 3 at%. Ru preferentially partitioned to the γ phase, and its partitioning ratio to the γ phase increased with a variation in Ru content from 1 at% to 3 at% and decreased for the NiAl6Ru alloy. Additionally, the lattice misfit of all alloys was positive and reduced with the increase in Ru content, which hindered the Ru atoms to diffuse into the γ phase and promoted the shape of γ′ precipitates to change from cubic to spherical