Crystal structure and thermal stability of
martensite in Cu-24Al-3Mn alloy
martensite in Cu-24Al-3Mn alloy
(1. Department of Materials Science and Engineering,
Central South University, Changsha 410083, China;
2. Department of Materials Science and Engineering,
Hefei University of Technolo gy, Hefei 230009, China)
Central South University, Changsha 410083, China;
2. Department of Materials Science and Engineering,
Hefei University of Technolo gy, Hefei 230009, China)
Abstract: The crystal structure and thermal stability of the martensite in Cu-24Al-3Mn ( mole fraction, %) alloy were studied by X-ray diffraction, electron diffraction, V—t curve measurement. The 18R martensite with fairly perfect long-range order can be obtained by water-quenching the alloy. The atoms distribution on the basal plane of the martensite is as follows: Ⅰ, 3/25 Mn+22/25 Cu; Ⅱ , 3/25 Al+22/25 Cu; Ⅲ, 18/25 Al+7/25 Cu, correspondingly, the parent phase may h ave Heusler structure. From the electron diffraction result, the crystal structu re is determined to be of a modified 18R type but closely approaching orthorhom bic 18R type, its lattice parameters are determined to be a=0.4474nm, b=0.5229nm, c=3.815nm and β=89.6° from the X-ray diffraction results. The obtained alloy has a higher thermal stability than that of the conventional Cu-Zn-Al alloy.
Key words: shape memory alloy; Cu-Al-Mn alloy; martensite; crystal structure; thermal stability