Glass Forming Ability and Mechanical Properties of Misch Metal-Based Bulk Metallic Glass Matrix Composite

Abstract

The effect of replacement of lanthanide by misch metal (Mm) in La-Al-TM (TM; transition metal, Ni, Cu and Co) alloys has been investigated to evaluate the possibility of fabrication of in-situ glass matrix composites with enhanced properties. For the as-cast cylindrical Mm₅₅Al₂₅Ni₁₀Cu₁₀ alloy ingot with 3 mm diameter, the microstructure is consisted of two kinds of a few μm size crystalline phases (volume fraction: 4.6%) uniformly distributed in the metallic glass matrix. The substitution of La by Mm reduces the glass forming ability (GFA), i.e., lower the reduced glass transition temperature, T_rg (= T_g/T_L, where T_L is the liquidus temperature) and smaller superliquid temperature region, ΔT_x (= T_x - T_g, where, T_g is the glass transition temperature and T_x the onset temperatures of crystallization), enabling the fabrication of in-situ BMG matrix composite. The Mm₅₅Al₂₅Ni₁₀Cu₁₀ metallic glass matrix composite sample exhibits the compressive fracture strength of 931 MPa, and in particular enhanced the compressive plastic strain of 1.2% before failure. The enhanced strength and ductility was explained by the presence of fine crystalline phases embedded in the BMG matrix, which led to a multiple shear band formation.