Glass-forming ability, thermal stability, mechanical and electrochemical behavior of Al-Ce-TM (TM = Ti, Cr, Mn, Fe, Co, Ni and Cu) amorphous alloys

Abstract

Al86Ce10TM4 amorphous alloys (TM = Ti, Cr, Mn, Fe, Co, Ni and Cu; where the alloys are denoted by A1~A7, respectively) were fabricated using melt-spin fast-quenching method. The glass-forming ability (GFA), thermal stability (TS), and mechanical and corrosion behavior of the as-spun alloys were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS), differential scanning calorimetry (DSC), micro-indentation and electrochemical techniques. It was found Al and Ce microalloyed with Ti, Cr, Mn, Fe, Co, Ni and Cu, respectively enhance glass formation, thus the as-spun Al86Ce10TM4 alloys form an amorphous matrix embedded with short range ordered (SRO) Al-TM, Al-Ce and Al-Ce-TM quasi-crystalline clusters due to a strong heteroatomic interaction related to a covalent character of atomic bonds (for A1~A7) or/and inlaid with face-centered-cubic aluminum (FCC-Al) nano-crystallites which were precipitated during the melt-spin quenching (for A1~A3). The GFA of the alloys ranks in the sequence of A4 > A5 > A6 > A7 > A2 > A3 > A1 which can be assessed by the supercooled liquid region ΔTm (=Tm-Tx), the reduced glass transition temperature Trg (=Tg/Tm), and other criteria such as γ′ = Tx/(Tg + Tm), δ′ = Tx/(Tm − Tg), β′ = TxTg/(Tm + Tx)2, and ω′ = Tm(Tm + Tx)/(Tx(Tm − Tx)); while the TS of the alloys lists in the series of A5 > A6 ~ A4 > A7 > A3 > A2 > A1 that can be evaluated by the first crystallization activation energy Ec, first crystallization activation enthalpy ΔH⁎, frequency factor Ko, fragility parameter m, and theoretical glass transition temperature Tg⁎. The hardness of the alloys A1~A7 accounts to 707, 809, 940, 863, 762, 809, and 715 MPa, respectively, attributing to a composite structure consisting of an amorphous matrix tessellated with SRO quasi-crystalline clusters or/and FCC-Al nano-crystallites. In addition, the alloys exhibit high corrosion resistance in the rate of 10−7–10−8 A/cm2 with a large passivation scope except that the alloy A7 presents a corrosion rate of 10−6 A/cm2 with an active anodic dissolution behavior. The results manifest the Al86Ce10TM4 alloys can be fabricated into a unique composite consisting of an amorphous matrix embedded with SRO quasi-crystalline or/and nano-crystalline phases which confers high mechanical hardness and corrosion resistance for potential engineering applications. Keywords: Amorphous alloys, Glass-forming ability, Thermal behavior, Al-Ce-TM, Electrochemistry