Liquidmetal
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- Liquid Metal is also a name for Galinstan, a fusible alloy liquid at room temperature, used as a replacement of mercury.
Liquidmetal and Vitreloy are commercial names of a series of amorphous metal alloys developed by a California Institute of Technology research team, now marketed by a firm that the team organized called Liquidmetal Technologies.
A range of zirconium-based alloys have been marketed under this trade name. Some example compositions are listed below, in atomic percent:
- An early alloy, Vitreloy 1:
- A variant, Vitreloy 2, or Vit2:
- Vitreloy 105, or Vit105:
- A more recent development (Vitreloy 106a), which forms glass under less rapid cooling:
The alloys contain atoms of significantly different sizes, leading to low free volume (and therefore high viscosity) when melted. The viscosity prevents the atoms moving enough to form an ordered lattice. The material structure also results in low shrinkage during cooling, and resistance to plastic deformation.
The zirconium and titanium based Liquidmetal alloys achieved yield strength of over 1723 MPa, nearly twice the strength of conventional crystalline titanium alloys, and have superior elasticity, up to three times of other alloys. The alloys have relatively low melting point in comparison with melting points of their components, allowing casting of complicated shapes without need of finishing. The material properties immediately after casting are much better than of conventional metals; usually, cast metals have worse properties than forged or wrought ones. The lack of grain boundaries in a metallic glass eliminate grain-boundary corrosion - a common problem in high-strength alloys produced by precipitation hardening and sensitized stainless steels. No grain boundaries also eliminates grain-boundary dislocation pile-up mechanism of crack initiation and buildup of gas dissolved in the metal precipitating at boundaries. The alloys are malleable at low temperatures (400 °C for the earliest formulation), and can be molded like thermoplastics. [1]
The high elasticity and lack of plastic deformation before onset of catastrophic failure limits the material applicability in reliability-critical applications, as the impending failure is not evident. The material is also susceptible to material fatigue with crack growth; a two-phase composite structure with amorphous matrix and a ductile dendritic crystalline-phase reinforcement, or a metal matrix composite reinforced with fibers of other material can reduce or eliminate this disadvantage. [2]
Due to their non-crystalline (amorphous) structures, the materials are harder and more elastic than alloys of titanium or aluminum used in similar applications. The technology has made its way into consumer, military and industrial fields, most visibly in sports equipment such as skis, baseball bats and softball bats, and racquets. In golf clubs, the first commercial use of the material, Liquidmetal rods and head parts are used, as the material absorbs less energy, allowing more efficient transfer of energy to the ball; some golf balls feature Liquidmetal inner core. [3] The material has also found its way into the casing of a late-model SanDisk "Cruzer Titanium" USB flash drives as well as their Sansa line of flash based MP3 player, and casings of some cellphones (like the luxury Vertu products) and other toughened consumer electronics. It is also considered as a replacement of titanium in applications ranging from medical instruments and cars to military and aerospace industry. In military applications, rods of amorphous metals are considered as a replacement of depleted uranium in kinetic energy penetrators. Plates of Liquidmetal were used in the solar wind ion collector array in the Genesis space probe.
Due to their corrosion and wear resistance, Liquidmetal alloy layers can be used as protective coatings for industrial machinery, including oil drill pipes and power plant boiler tubes.
