The efficiency assessment of Ni₍₄₀₎Ti₍₅₀₎Cu_(x)Fe_(10−x) shape memory alloy produced by combustion synthesis through thermal analysis

In this investigation, Ni₍₄₀₎Ti₍₅₀₎Cu_(x)Fe_(10−x) (x = 2.5, 5, 7.5) alloys were synthesized through the self-propagating high-temperature synthesis (SHS) process, employing preheating temperatures of 240 and 450 °C. To optimize thermal analysis, samples were drawn from the middle and upper sections of specimens exhibiting superior propagation results at a preheating temperature of 450 °C. Omitting additional heat treatment ensured a precise result interpretation. While the Ti₅₀Ni₄₀Fe_2.5Cu_7.5 sample displayed minimal variations in martensite and austenite transformation temperatures, others exhibited diverse transformation profiles. Apart from the B19' martensitic phase, distinct B19 martensitic phases were identified in Ti₅₀Ni₄₀Fe₅Cu₅ and Ti₅₀Ni₄₀Fe_2.5Cu_7.5 alloys, each showcasing unique transformation temperatures and full-width at half-maximum (FWHM) values. The inquiry unveiled that an increased Fe content prompted the segregation of Fe_x(Ni)Ti-based intermetallic phases from Cu-based phases, with this effect intensifying in alloys featuring higher Fe atomic ratios. This influence significantly impacted transformation temperature outcomes, overshadowing the inherent impact of the synthesis method.