Study Of Decomposition Of Thermoelastic And Non-thermoelastic Martensite In Cu-Zn-Al Alloys

Abstract

Abstract. Cu based alloys are considerable traditional material with good shape memory effect. Reversal thermoelastic transformation from parent phase to martensite is necessary requirement for taking place of shape memory effect. The significant phase for taking place shape memory effect in CuZnAl alloy is ordered β phase with ideal ratio of valence electrons to atom e/a = 1.48. The alloys with ratio e/a lesser than 1.42 after quenching from single phase beta region undergo non-thermoelastic martensitic transformation and thereby don't possess shape memory effect. This can be obtained by quenching from dual phase α + β region in some alloys. The paper deals with comparison of decomposition at elevated temperatures of thermoelastic and non-thermoelastic martensite to more stable products. Influence of stabilization of martensite on decomposition at elevated temperatures is also studied. Depending up initial state of material and condition of decomposition it could be possible to obtain structure containing α and β or γ phase with miscellaneous morphology and it could be possible to used for modification of definitive structure or for modification of structure before another heat treatment. Study of differences between thermoelastic and non-thermoelastic martensities would be useful for intensification of shape memory properties of Cu based alloys.

Indentation Measurement of CuZnAl Dual Phase Shape Memory Alloy

“…Although some studies to estimate the mechanical properties of this material were published [3], any serious research in this field of study on dual phase shape memory alloys is missing. From this point of view, presented study is continuation of extensive research of Longauer and co-workers on Cu-22Zn-4.6Al shape memory alloy [1,2,3,4].…”

“…In the work [2] the change of the portion of thermoelastic and non-thermoelastic martensite in dependency of quenching temperature was studied by means of decomposition annealing. It was found, that volume fraction of non-thermoelastic martensite is raised with increasing quenching temperature, resulting in a gradual loss of shape memory effect.…”

“…The shape memory effect disappears with increasing quenching temperature, that is increasing martensite volume fraction in this alloy. There were published several works explaining paradoxical decreasing of shape memory effect with quenching temperature rising [1,2]. In the work [2] new approach to explaining paradoxical decreasing of shape memory effect by means of change of thermoelastic and non-thermoelastic martensite ratio in structure was proposed.…”

“…There were published several works explaining paradoxical decreasing of shape memory effect with quenching temperature rising [1,2]. In the work [2] new approach to explaining paradoxical decreasing of shape memory effect by means of change of thermoelastic and non-thermoelastic martensite ratio in structure was proposed. Although some studies to estimate the mechanical properties of this material were published [3], any serious research in this field of study on dual phase shape memory alloys is missing.…”

Use of Decomposition of Non-Thermoelastic Martensite for Structural Changes of CuZnAl Shape Memory Alloys

“…In previous works [4,5] it was found that increasing of quenching temperature causes increased ratio of non-thermoelastic martensite at the expense of thermoelastic one. It can be assumed that there is different behaviour of thermoelastic and non-thermoelastic martensice at heating.…”