Rejuvenation, embryonic shear bands and improved tensile plasticity of metallic glasses by nanosecond laser shock wave

Abstract

The influence of three polymer dispersions [styrene-butadiene copolymer (SB), styrene-acrylic ester copolymer (SA) and polyacrylic ester (PA)] on the hydration of calcium sulfoaluminate (CSA) cement within 72 h was investigated by using isothermal conduction calorimetry, X-ray diffraction analysis and thermal gravimetric analysis. The results indicate that these three polymer dispersions perform different influences on the hydration heat flow of CSA cement during different periods, they all postpone the occurrence time of the maxima peaks, and its extent is mainly dependent on the addition amount. Polymer dispersions manifest great retardation on the initial hydration of CSA cement, and the effect is much more significant within 1 h. In this stage, the generation of ettringite is strongly delayed; however, the formation of ettringite is accelerated by these polymer dispersions at and after 2 h. Among these three polymer dispersions, PA demonstrates the highest acceleration effect on the hydration degree.

Effect of Surface Mechanical Attrition Treatment on Micro-mechanical Properties of ZrCuAlNi Bulk Metallic Glass

“…It is also should be noted that the decrease in the generation of defects and stored energy in S15 leads to the enhancement of hardness and Young's modulus than that analyzed in S10. From these results, it is concluded that the increase in stored energy in the amorphous solids is directly related to the rise in structural defects, heterogeneity and distribution of dynamic modulus, while it has an inverse correlation with the hardness and Young's modulus, which is also reported in other works 18,29,[37][38][39][40] . Finally, it should be noted that the SMAT time was in the range of 0 up to 15 min with 5-min intervals.…”

Abnormal softening of Ti-metallic glasses during nanosecond laser shock peening

“…The structural rearrangement of MGs can be determined by the cooperative shear motion of STZ, which inherently depends on the activation volume. From the perspective of the "structural rejuvenation theory" [12,37], additional free volume or flow unit was preferentially activated in the subsurface region, the number and size of STZ should be the largest, which is contrary to the above-mentioned results. Thus, an unknown mechanism accounting for the change of Ω may exist, directing the interaction between solid and wave propagation.…”

“…NLSP can also be recommended as an effective method for reducing brittleness in metallic glasses (MGs). The effect of NLSP on the mechanical properties has been studied widely, which is beneficial for plasticity improvement in MGs due to the appearance of the extra-deep residual stress region, structural rejuvenation and abundant embryonic shear bands [10][11][12][13]. In addition, the combined effect of high hydrostatic and shear stresses was found to be able to induce a crystalline-to-amorphous transformation when the shock pressure was above a critical threshold value [14,15].…”