IN-SITU TEM STUDY OF THE NI5AL3 TO B2+LL(2) DECOMPOSITION IN NI65AL35

Homogenised and quenched Ni65Al35 samples were heated and studied in s itu in a CM20 electron microscope up to 900 degrees C. The Ni5Al3 phas e first forming around 550 degrees C in the quenched L1(0) microtwinne d martensite starts to decompose around 800 degrees C yielding B2 prec ipitates in a twinned L1(2) matrix. The latter twinning is a remainder of the microtwinning in the original room temperature martensite. Als o the crystallographic relations between precipitates and matrix can b e traced back to the original formation of twinned martensite plates w ithin the austenite. Some aspects of the dynamics of the process are d iscussed on the basis of snap shots and video recordings.