The two way memory effect in TiNi alloys

Journal Article · Thu Aug 01 00:00:00 EDT 1996 · Scripta Materialia

DOI:https://doi.org/10.1016/1359-6462(96)00162-5· OSTI ID:271581

Filip, P; Mazanec, K ^[1]

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1. Technical Univ. of Ostrava (Czech Republic). Inst. of Materials Engineering

The two way memory effect (TWME) in shape memory alloys represents a reversible spontaneous shape changes during cooling and heating processes. This is a consequence of reversible phase transformations observed without application of any external stresses. The TWME is usually obtained after a thermomechanical treatment often called training. The different opinions were published concerning the influence of R-phase formation in TiNi based alloys on the stability of TWME. Stachowiak and McCormick have stated that the formation of R-phase diminishes the extent of obtained reversible strain as well as the stability of TWME. In contrast to this conclusion, the authors observed enhanced stability of TWME in the cases when the R-phase formation precedes the martensitic transformation B2 {yields} B19{prime}. Repeating the heating cycles at loading of the memory materials, the complex degradation mechanisms of TiNi alloys occurs. The dislocation generation in the matrix of TiNi alloys (work hardening) strongly influences the maximum level of generated stresses and the extent of reversible strain. As a contribution to the explanation of physical principles of TWME, the present paper is devoted to the study of substructure after so called hard training at which the specimens are deformed ({var_epsilon} = 4%) and cyclically heated and cooled down at constrained conditions.

• OSTI ID: 271581
• Journal Information: Scripta Materialia, Vol. 35, Issue 3; Other Information: PBD: 1 Aug 1996
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
TITANIUM ALLOYS
PHASE TRANSFORMATIONS
SHAPE MEMORY EFFECT
MICROSTRUCTURE
NICKEL ALLOYS
INTERMETALLIC COMPOUNDS
WIRES
COLD WORKING
DRAWING
ANNEALING
THERMOMECHANICAL TREATMENTS
TRANSITION TEMPERATURE
MARTENSITE
AUSTENITE
TRIGONAL LATTICES
TRANSMISSION ELECTRON MICROSCOPY
DISLOCATIONS