Hot rolled specimens of low-manganese Fe-Mn-Si-Cr-Ni shape memory alloys, produced by classical and by powder metallurgy (CM and PM) with mechanical alloying, respectively, were analysed by tensile loading-unloading tests (TENS), by dilatometry (DIL), by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Solution annealed specimens had two-phase structure, comprising γ-austenite and thermally induced α-martensite. The formation of

The thermally and stress induced phase transitions occurring in a Cu-Al-Mn Shape Memory Alloy (SMA) have been investigated by means of thermal analysis techniques, tensile testing and microscopic observations. On heating a hot rolled solution annealed Cu-Al-Mn SMA, up to 873 K, two phase transformations, related to equilibrium phase precipitation and to 2-step order-disorder transition, respectively, were revealed by Differential Scanning Calorimetry

The paper assumes that, in the case of a martensitic Cu-Zn-Al shape memory alloy subjected to heating above 770 K, the endothermic peaks revealed by differential scanning calorimetry (DSC) and differential thermal analysis (DTA) and located around 630 K would correspond to the transitory formation of α1 bainite. This endothermic phenomenon has been regarded as transitory since heating proceeding causes exothermic precipitation of equilibrium α-phase

It is well-known that one way shape memory effect (SME) in Fe-Mn-Si based shape memory alloys (SMAs) is related to the thermally-induced reversion of ε (hexagonal close packed, hcp) stress induced martensite (SIM) to γ (face centered cubic , fcc) austenite. In the case of an Fe-Mn-Si-Cr-Ni SMA this reverse martensitic transformation was analyzed in regards to the critical temperature for the beginning of austenite formation (As) in different states

By means of displacement-temperature variation curves, the occurrence of work developing shape memory effect (SME) was revealed in the case of helical springs made from a Cu-Al-Ni shape memory alloy, obtained by investment casting. The corresponding critical temperatures of martensitic transformation, determined on springs trained by SME cycling, were compared to the results obtained by differential scanning calorimetry (DSC) and by dilatometry,

After a brief review of the "friction reversion mechanism" during ultrasonic vibration drawing of tubes (UVD), the paper introduces a method to determine the drawing force based on the theorem of total consumed power, in the case of tube processing. The experiments performed on tubes made from 10TiNiCr180 (AISI321) austenitic stainless steel confirm the superiority of UVD technology as compared to classical technology (CT) regarding the diminution

Some prolonged exposure effects at the high temperatures and pressures characteristic to the steam transport in power station, have been revealed in a 12HMF GOST (13CrMo44 DIN) Cr-Mo low alloy steel pipes, at both macro and microstructural level, by mechanical tests and optical microscopy. After 128625 functioning hours, a marked mechanical degradation was noticed by the values of tensile strength, hardness and toughness that decreased with 14-16

The paper introduces ultrasonic vibration drawing (UVD) as a new technology for processing high mechanical resistance wires. A calculation method has been developed for the drawing force based on the theorem of total consumed power, considering a spherical rate field, a static flow, a Coulomb-type friction and the existence of the “reversion mechanism of average friction force” at metal-tool contact when the die is located in the oscillation

The mechanism of reversible transformation-induced plasticity of an Fe-30Mn-6Si (mass %) shape memory alloy, under tensile stress and subsequent compression, has been observed by optical and atomic force microscopy. The tensile stress-induced e (hexagonal close-packed) martensite reverts into c (face-centered cubic) austenite after compression to zero strain. Further compression to negative strains induces a different e martensite variant from that

Free- and constrained recovery behaviors of a Fe-23.3 Mn-2.8 Si (wt. %) Shape Memory Alloy (SMA) were revealed by uncoiling experiments and tensile tests, respectively. With the enhancement of plastic deformation degree, including by additionally elongating the hot rolled specimens, the increase of the amount of ε stress induced martensite (SIM) plates in the detriment if γ austenite, was emphasized by means of optical microscopy and XRD. The tensile-stress