Mechanical properties of a new high specific strength honeycomb from amorphous metal

Abstract

Using metallic glasses as base materials, Amorphous Metal Honeycombs (AMHs) with a teardrop cellular geometry were manufactured. A new analytical model was proposed to predict the relative density and axial compressive strength of teardrop celled AMHs. Using this, an optimum theoretical density at which axial compressive strength of AMHs exceed theoretical strengths of aluminum honeycombs were predicted. Results from experimental testing of AMHs in the density range of 0.3 Mg/m3 to 0.6 Mg/m3 validate the proposed analytical model. AMH with a density of 0.6 Mg/m3 and cell size of 1.1 mm showed a higher axial compressive strength compared to aluminum honeycombs. The proposed model also shows that a higher maximum yield stress is achievable by improving inter-cellular bonding. A successful welding method has been demonstrated to join amorphous Fe45Ni45Mo7B3 ribbons at a higher cooling rate. XRD studies on welded samples from this method do not show crystallization. Ribbons remained amorphous before and after the weld. By improving the cooling rate of the weld, crystallization was avoided maintaining the strength of the weld. Using a method similar to peening, significant curvatures were observed in amorphous Fe45Ni45Mo7B3 ribbons. While the prediction of a tempering state would imply a residual compressive surface stress upon layer removal, peening of amorphous ribbons showed an opposite response. The amorphous phase of peened ribbons remained, as evident from XRD data. SEM micrographs show distorted ribbon edges and an average thickness reduction of 10% after peening also confirmed by X-ray transmission measurements. Young's modulus and yield strength measured from bulk tension testing of the in-plane direction did not show a significant change as a result of peening.