Influence of Fe Addition on Phase Transformation, Microstructure and Mechanical Property of Equiatomic NiTi Shape Memory Alloy

Abstract

Based on equiatomic nickel and titanium, three kinds of NiTiFe alloys with a nominal chemical composition of Ni 49 Ti 49 Fe 2 , Ni 48 Ti 48 Fe 4 and Ni 47 Ti 47 Fe 6 (at.%), respectively, have been designed to investigate the influence of the addition of Fe element on phase transformation, microstructure and mechanical property of equiatomic NiTi shape memory alloy. The microstructures of three kinds of NiTiFe alloys are characterized by the equiaxed grains instead of the dendrites. Consequently, some Ti 2 Ni precipitates are found to distribute in the grains interior and at the grain boundaries. The content of Fe element has an important influence on mechanical property of NiTiFe alloy. With increasing content of Fe element, the strength of NiTiFe alloy increases substantially, but the plasticity decreases sharply. It can be concluded that precipitation strengthening and solution strengthening play a significant role in enhancing the strength of NiTiFe alloy. In the case of three NiTiFe alloys, neither martensitic transformation nor reverse transformation can be observed in the range from-150 to 150°C. On the one hand, the phase transformation temperature is probably out of the scope of the present experimental temperature. On the other hand, the addition of Fe element probably suppresses first-order martensitic transformation or reverse transformation, and consequently the second-order-like phase transformation from an incommensurate stage to a commensurate stage can probably take place.

Experimental investigation of the effects of aging and cryogenic treatments on the mechanical properties of superelastic nickel-titanium shape-memory alloys

“…In smart materials, the initial temperature of the martensitic transformation decreases in cases of reduced Ni and increased Fe ratios. 48 Moreover, researchers have stated that martensitic transformation could not occur after the addition of Fe to NiTi alloys. 48 Figure 5(b) gives the EDX analysis data taken from the fracture surfaces of the cryogenic and aging heat-treated sample (S2).…”

“…48 Moreover, researchers have stated that martensitic transformation could not occur after the addition of Fe to NiTi alloys. 48 Figure 5(b) gives the EDX analysis data taken from the fracture surfaces of the cryogenic and aging heat-treated sample (S2). The element C was heavily present on the surface.…”

“…48 Moreover, researchers have stated that martensitic transformation could not occur after the addition of Fe to NiTi alloys. 48…”

Effects of Predefined Thermomechanical Procedure on the Microstructure and Mechanical Properties of the Two-Way Shape Memory Effect in the NiTi Alloy

“…Previous research on TWSME focused on the generation, explanation, and impact of various parameters on the magnitude of this efect [12,13]. Additionally, the impact of applying various prestrains and deformation was previously investigated on various NiTi alloy types with the addition of third alloy elements [14][15][16][17]. Qader et al [18] studied the efect of boron elements on microstructure evolution and thermomechanical properties of a Ni-riched NiTi shape memory alloy.…”

Ti50Ni27Nb20Ta3 Şekil Hatırlamalı Alaşımda Isıl İşlemlerin Faz Dönüşüm Histeresizi ve Termal Aktivasyon Enerjisi Üzerine Etkilerinin İncelenmesi

“…Genel olarak, R (rombohedral faz) fazı, B19 / fazından önce gözlemlenen kademeli dönüşümü temsil etmektedir. NiTi bazlı şekil hatırlamalı alaşımların ısıl işlem ve kimyasal bileşimi, dönüşüm sıcaklıklarını etkileyen önemli faktörlerdir [14].Bu alaşımlara katkılanan Pd, Hf, Pt ve Zr martensit dönüşüm sıcaklıklarını, histerisizlikleri ve termomekaniksel karakteristiklerini arttırmak için eklenirken; Fe, Al, Mo ve Nb elementlerinin katkılanması bu karakteristikleri azaltmaktadır [14,15]. Üçlü NiTiNb ŞHA'lar üzerine araştırma olmasına rağmen, dörtlü NiTiNbTa alaşımı ve bunlara uygulanan termal iyileştirmeyi araştıran çalışmalar yok denecek kadar azdır.…”