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Publicatii proprii
A structural-morphological study of a Cu63Al26Mn11 shape memory alloy
By means of DSC, three transformations occurring on heating up to 873 K, of a martensitic Cu63Al26Mn11 Shape Memory Alloy (SMA) in hot pressed and homogenized state, were revealed. The assumed precipitation of α-phase, accompanied by an exothermic reaction, was ascertained by SEM mapping. SEM micrographs revealed preferred orientation tendencies for the α-phase precipitates, inside the grains which became more prominent along grain boundaries
Read moreStudy of the transitory formation of α1 bainite, as a precursor of α-
Bainite transitory formation, during the heating of a martensitic copper base SMA, was predicted by DSC and DTA and confirmed by XRD, OM and TEM only in hot pressed air cooled state homogenized and tempered at 573 K. In this heat treatment state, due to the pre-existence of α-phase, bainite amount is expected to be too low, therefore nondistinguishable, for higher tempering temperatures, where it is suggested that transitory α1 bainite turned to
Read moreHeating rate effects on reverse martensitic transformation in a Cu–Zn–Al shape memory alloy
Different fragments of martensitic Cu-14.86 Zn-5.81 Al-0.5 Fe (mass. %) shape memory alloy were subjected to heating, up to 453 K, with different rates ranging from 1 K×1.66×10 2 s 1 to 54.6×1.66×10 2 s 1, performed by means of a differential scanning calorimeter. In all cases, during heating, an endothermic peak was observed which was associated with the martensite reversion to parent phase. By means of the differential scanning calorimeter
Read moreNew calorimetric-structural aspects of temperature memory effect in hot rolled Cu-Zn-Al SMAs
Temperature memory effect (TME) is usually manifested by a kinetic stop during reverse transformation of thermally induced martensite to parent phase, after performing an incomplete heating in the previous thermal cycle, applied to a shape memory alloy (SMA). Technically TME causes the splitting of the endothermic peak corresponding to martensite reversion, on differential scanning calorimetry (DSC) thermograms. The present paper illustrates new
Read moreMechanical alloying effects on the thermal behaviour of a Fe-Mn-Si-Cr-Ni shape memory alloy under powder form
By means of simultaneous thermal analysis (STA), comprising differential scanning calorimetry (DSC) and thermal gravimetry (TG), a repetitive solid state transformation has been observed which was associated with Ni ferromagnetic-paramagnetic transition within the powders of an Fe-based shape memory alloy (SMA) with nominal composition Fe-14 Mn-6 Si-9 Cr-5 Ni (mass. %). During thermal cycling up to 773 K an obvious exothermic step on heating and
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