Preparation, microstructure and mechanical properties of tungsten fiber reinforced LaAlCuNi metallic glass matrix composites

Highlights

• W_f/La₆₂Al₁₄Cu₁₂Ni₁₂ bulk metallic glass composites were successfully prepared by a new forward melt infiltrating method.

• The composite with fiber volume fraction of 60% shows a significant plastic strain of 11.7% as well as a high fracture strength of 1600 MPa.

• Compared with W_f/Zr-based BMGCs, the preparation of W_f/La₆₂Al₁₄Cu₁₂Ni₁₂ BMGCs is simpler and more convenient.

Abstract

In this paper, W_f/La₆₂Al₁₄Cu₁₂Ni₁₂ bulk metallic glass composites (BMGCs) were successfully prepared by a new forward melt infiltrating method. Compared with W_f/Zr-based BMGCs, the preparation of W_f/La₆₂Al₁₄Cu₁₂Ni₁₂ BMGCs is simpler and more convenient. In the experimental part, quasi-static compressive behaviors of composites with different fiber volume fractions were systematically investigated. The volume fraction of the tungsten fiber was found to have remarkable influence on compressive properties and fracture modes of the composites. The introduction of tungsten fiber can significantly improve the strength of composites, strikingly, the composite with fiber volume fraction of 60% shows a significant plastic strain of 11.7% as well as a high fracture strength of 1600 MPa. With the increasing fiber volume fraction, the failure mode of the composites switches from shear of amorphous matrix to splitting. In addition, the relationship between compressive strength and fiber volume fraction of W_f/La₆₂Al₁₄Cu₁₂Ni₁₂ BMGCs and W_f/Zr(Vit1)-based BMGCs was studied, and we found that the theoretical compressive strength of those two composites is approximately consistent with the experimental counterparts. Although the matrix strength of the two varieties of composites has a huge difference, the compression plasticity of composites shows a similar change with the increasing fiber volume fraction.

Introduction

Bulk metallic glasses (BMGs) are known for their excellent properties including good corrosion resistance, high wear resistance, high strength, high hardness, good soft magnetism and low magnetic loss, it is a new class of material with great application potential [1,2]. Unfortunately, BMGs cannot slip and twine like crystalline materials during deformation, resulting in catastrophic brittlement failure during deformation at room temperature. The extrinsic approaches to improve the plasticity of BMGs are exploring BMG composites [3]. By introducing in-situ or ex-situ second phases into the BMG matrix, the BMGCs have yielded improvements in tensile and compressive strains before failure. For instance, the in-situ BMGCs like La-based BMGCs with α- La dendrites [4], Fe-based BMGCs with α-Fe dendrites [5], CuZr-based BMGCs with B2–CuZr crystals [6] and the Ti-based BMGCs with metastable and transformable beta-Ti dendrites [7], which often shows large tensile plasticity and good work-hardening capacity. The increase in ductility is mainly attributed to that the second phase can effectively prevent the brittle fracture caused by the slip of a single shear band and promote the nucleation and propagation of multiple shear bands. These multiple shear bands can accommodate much plastic strain, which contributes to macroscopic plasticity [8]. As a kind of second crystalline material, metal fiber can effectively improve the strength and plasticity of BMGCs. The metal element tungsten has stable chemical properties, small thermal expansion coefficient, high strength, high hardness, good anti-oxidation and anti-corrosion properties, which makes it an ideal candidate as second crystalline phase in BMGCs.

Zr-based BMGs generally possess a strong glass forming ability (GFA), wide supercooled liquid region, high strength and high toughness, and can be applied into many fields [9,10]. BMGCs with Zr-based BMGs as matrix and tungsten fiber (W_f) as the second phase have been widely studied [[11], [12], [13], [14], [15]]. Despite all this, the preparation of W_f/Zr-based BMGCs is still complicated, and the interface reaction can usually happen between tungsten fiber and amorphous melt during the process of preparation [[16], [17], [18], [19]]. Furthermore, the Zr-based amorphous alloys have a relatively high liquidus temperature (T_l) [1], in turn, leading to a higher preparation temperature of W_f/Zr-based BMGCs, and consequently a great internal stress will occur in the composites [20]. In addition, oxygen, in particular, strongly affects the GFA of Zr-based amorphous alloys [[21], [22], [23]]. It means that the tube will be evacuated several times to remove any residual oxygen during the preparation of composites [24]. Among all of metallic glass former systems, La-based BMGs have a strong GFA and lower liquidus temperature (T_l) [25], and more importantly, there is no intermediate phase between the elements La and W, and the La-based BMGs are also not sensitive to oxygen [25]. Therefore, it will be extremely convenient to fabricate BMGCs with tungsten fiber embedded in La-based BMGs matrix. Moreover, the La-based BMGs have attracted increasing interest due to their unique properties. For example, they can undergo superplastic deformation at a relatively low temperature [26]. And the strength of La-based BMGs is 600 MPa at room temperature [27], which is comparable to Al and Mg alloys [28]. While they have the similar softening points to traditional plastics, the strength is much higher than the latter. And the introduction of tungsten fiber into the La-based BMGs is expected to greatly improve their strength and plasticity. In this study, we have successfully prepared W_f/La₆₂Al₁₄Cu₁₂Ni₁₂ BMGCs by forward melt infiltrating casting method, and the effect of the fiber volume fraction (V_f) on the compressive behaviors of the W_f/La₆₂Al₁₄Cu₁₂Ni₁₂ BMGCs was systematically studied.