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International Journal of Energetic Materials and Chemical Propulsion
ESCI SJR: 0.149 SNIP: 0.16 CiteScore™: 0.29

ISSN Print: 2150-766X
ISSN Online: 2150-7678

International Journal of Energetic Materials and Chemical Propulsion

DOI: 10.1615/IntJEnergeticMaterialsChemProp.v8.i6.80
pages 571-593

HMX POLYMORPHISM: VIRTUAL MELTING GROWTH MECHANISM, CLUSTER-TO-CLUSTER NUCLEATION MECHANISM AND PHYSICALLY BASED KINETICS

Valery I. Levitas
Iowa State University, Departments of Mechanical Engineering, Aerospace Engineering, and Material Science and Engineering, Ames, Iowa 50011 USA
Laura B. Smilowitz
Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Bryan F. Henson
Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Blaine W. Asay
Los Alamos National Laboratory, Los Alamos, NM 87545, USA

ABSTRACT

A fully physically-based thermodynamic and kinetic model of the β ↵ δ phase transformation in energetic crystal HMX crystal embedded in polymeric binder is developed. It is based on a new nucleation mechanism via melt mediated nano-cluster transformation and the recently formulated growth mechanism via internal stress-induced virtual melting. During the nucleation, nano-sized clusters of β phase dissolve in a molten binder and transform diffusionally into δ phase clusters. During the interface propagation, internal stresses induced by transformation strain cause the melting of the stressed δ phase much below (120K) the melting temperature and its immediate resolidification into the unstressed δ phase. These mechanisms explain numerous puzzles of HMX polymorphism and result in local and overall transformation kinetics that are in good agreement with experiments.