4 research outputs found
A minimal integer automaton behind crystal plasticity
Power law fluctuations and scale free spatial patterns are known to
characterize steady state plastic flow in crystalline materials. In this Letter
we study the emergence of correlations in a simple Frenkel-Kontorova (FK) type
model of 2D plasticity which is largely free of arbitrariness, amenable to
analytical study and is capable of generating critical exponents matching
experiments. Our main observation concerns the possibility to reduce continuum
plasticity to an integer valued automaton revealing inherent discreteness of
the plastic flow.Comment: 4 pages, 5 figure
The role of phase compatibility in martensite
Shape memory alloys inherit their macroscopic properties from their mesoscale
microstructure originated from the martensitic phase transformation. In a cubic
to orthorhombic transition, a single variant of marten- site can have a
compatible (exact) interface with the austenite for some special lattice
parameters in contrast to conventional austenite/twinned martensite interface
with a transition layer. Experimentally, the phase compat- ibility results in a
dramatic drop in thermal hysteresis and gives rise to very stable functional
properties over cycling. Here, we investigate the microstructures observed in
Ti50Ni50-xPdx alloys that undergo a cubic to orthorhombic martensitic
transformation using a three dimensional phase field approach. We will show
that the simulation results are in very good agreement with transmission
electron microscopy observations. However, the understanding of the drop in
thermal hysteresis requires the coupling of phase transformation with plastic
activity. We will discuss this point within the framework of thermoelasticity,
which is a generic feature of the martensitic transformation.Comment: Accepted for publication in in Journal of Applied Physic
Fluorescence study on Al2O3-polystyrene latex composite film formation
This work reports a steady state fluorescence (SSF) technique for studying film formation from mixture of Al2O3 and polystyrene (PS) latex particles. The composite films were prepared from dispersion of pyrene (P)labeled PS particles in Al2O3 solution at room temperature and annealed at elevated temperatures in 10-min time interval above glass transition (T-g) temperature of polystyrene. Nine different composites film were studied in various latex contents. Fluorescence intensities (I-P) from P were measured after each annealing step to monitor the stages of film formation. No variations in I-p were detected for the films prepared with higher than 33 wt% Al2O3 content. However films prepared below 33 wt% Al2O3 content show considerable increase in I-P above the certain onset temperature called minimum film forming temperature, To. Healing temperatures T., were determined from the maxima of I-P. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 20 and 97 kJ.mol(-1), respectively.Publisher's Versio