The limits of glass formation by pulsed laser quenching in Nb-Ni alloys

Journal Article · Tue Oct 01 00:00:00 EDT 1991 · Scripta Metallurgica; (United States)

DOI:https://doi.org/10.1016/0956-716X(91)90002-I· OSTI ID:5768984

Vitta, S ^[1]

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1. Indian Inst. of Tech., Bombay (India)

This paper reports on the growth velocity of a crystal which from a liquid depends on the kinetics of atomic processes at the interface and the rate at which the heat of crystallization is removed from the interface. In the case of rapid quenching using pulsed lasers, the rate of heat removal following the laser pulse is very high due to the very small size of the liquid compared to the surrounding solid. The isotherm velocities are typically {gt}100 ms{sup {minus}1} and hence the crystal growth velocity is determined by the kinetics of atomic processes at the liquid- solid interface. The kinetics at the interface can be limited either by short range or long range atomic rearrangements depending on the alloy composition. The melt duration in a nanosecond laser quenching technique is {gt}5 ns. Atomic rearrangements requiring long range diffusive jumps are not possible in these time scales as the maximum diffusive speed in a liquid is only 10 ms{sup {minus}1}. Hence the crystal growth in dilute alloys has to be partitionless, occurring at velocities {gt}10 ms{sup {minus}1}. However, as the solute content in the alloy increases continuously, the long range diffusive constraints are expected to severly limit the crystal growth velocity. Since the isotherm velocities in the case of pulsed laser quenching are orders of magnitude higher than the diffusion limited crystal growth velocity, it should result in the formation of an amorphous or glass phase. Spaepen and Lin have observed a sharp transition from partitionless crystal growth to glass formation in the Fe-B system with as low as 5 at.% B due to the short range order required to form B clusters. In the case of metal-metal systems such a strong short range order is not always known to exist and hence the transition may not be as sharp as in the metal-metalloid systems.

• OSTI ID: 5768984
• Journal Information: Scripta Metallurgica; (United States), Vol. 25:10; ISSN 0036-9748
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
NICKEL ALLOYS
CRYSTAL GROWTH
NIOBIUM ALLOYS
AMORPHOUS STATE
GLASS
HEAT TRANSFER
ISOTHERMS
LASER-RADIATION HEATING
PULSES
QUENCHING
TIME DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
VELOCITY
ALLOYS
ELECTRON MICROSCOPY
ENERGY TRANSFER
HEATING
MICROSCOPY
PLASMA HEATING
360101* - Metals & Alloys- Preparation & Fabrication
360102 - Metals & Alloys- Structure & Phase Studies