In this study, the effects of nitrogen addition on the production of ultrafine/nano grained AISI 201L stainless steel by advanced thermo-mechanical process were investigated. Cast samples were first homogenized at 1200 °C for 4 h, hot-rolled at 1100 °C and finally, solution-annealed at 1150 °C for 2.5 h. Unidirectional and cross multipass cold rolling at 25 °C was carried out to 90% reduction i...

It has been clarified that deformation and annealing of martensite starting structure can produce ultrafine-grained structure in low carbon steel.  This study aims to investigate the texture evolution and mechanical properties of samples with martensite structure deformed by two different forging processes. The martensitic steel samples were forged by plane strain compression and multi-directio...

the unique properties of air-cooled bainitic steels have been described. a series of mn containing air-cooled bainitic steels invented by authors is presented in this paper: including low carbon granular bainitic steels, low carbon grain-boundary allotriomorphic ferrite/granular bainite duplex steels, medium and medium high carbon bainite/martensite duplex steel, and low carbon carbide free bai...

Magnetic shape memory properties of Ni-Mn-Ga single crystals were characterized by measurement of stress-induced martensite reorientation under constant magnetic fields. Also magnetic field-induced strain as a function of the applied magnetic field under different constant compressive stress levels has been investigated. All the experiments were performed at room temperature in which the sample...

Differential scanning calorimetry (DSC) was used to determine the transition temperature ranges (TTR) of four types of super-elastic orthodontic nickel-titanium coil springs (Sentalloy). A knowledge of the TTR provides information on the temperature at which a NiTi wire or spring can assume superelastic properties and when this quality disappears. The spring types in this study can be distingui...

The crystallography of B2 to R-phase and the subsequent R-phase to B19′ martensite transitions was analysed in NiTi alloys. Using the energy minimization theory of martensitic transformations, the habit plane and twin plane normals were established for the R-phase, B19′ martensite variants as a function of rhombohedral angle . Two types of twins, classified as {1 0 0}〈0 1 1〉 and {1 1 0}〈0 0 1〉 ...

Austenitic NiTi samples were cathodically charged with hydrogen to produce concentrations ranging from a baseline value of 9 wppm to 650 wppm. The effect of hydrogen on the phases and transition temperatures of NiTi was studied with X-ray diffraction (XRD), differential scanning calorimetry (DSC), tensile testing, and scanning electron microscopy (SEM). XRD analyses showed the B2 peaks shifting...

Near-equiatomic Ni-Ti, known for its shape memory behavior, can decompose to martensitic phases and/or second phase compounds. This phase competition is investigated in NixTi100-x (49<x<55) in as-quenched (AQ) and shock-loaded states. Dynamic loading was done with direct drive laser pulses of nanosecond duration; shocked samples were recovered for analysis. Unexpectedly, the lowest-Ni alloy (x ...

Abstract--In this investigation, the fracture surfaces of SS 304 and SS 316 austenitic steels were analysed using the X-ray fractography technique. In both cases, a decrease in the austenite content was observed at the fracture surface as a result of deformation induced martensite, indicating a linear relation with Km~ within the stable crack growth region. The presence of this martensite was f...

Shape memory alloys are typical temperature-sensitive metallic functional materials due to superelasticity and shape recovery characteristics. The conventional shape memory effect involves the formation and deformation of thermally induced martensite and its reverse transformation. The shape recovery process usually takes place over a temperature range, showing relatively low temperature-sensit...