Experiment and theoretical prediction of martensitic transformation crystallography in a Ni–Mn–Ga ferromagnetic shape memory alloy

A detailed study of martensitic transformation crystallography and microstructural characteristics in the Ni53Mn25Ga22 ferromagnetic shape memory alloy (FSMA) was performed by both experimental observation and theoretical calculation. It is revealed that there are two microscopically twin-related martensitic variants with a misorientation of ∼82° around the 〈1 1 0〉_M axis in each initial austenite grain. The twin interface plane was determined to be {0.399 0.383 0.833}_M (1.79° away from {1 1 2}_M). The ratio of the amounts of the two variants inherited from one single austenite grain is about 1.70. The prevalent orientation relationship between austenite and martensite was found to be Kurdjumov–Sachs (K–S) relationship with (1 1 1)_A//(1 0 1)_M, [110]A//[111]_M. A successful explanation of the crystallographic features during martensitic transformation will shed light on the development of FSMAs with optimal performance.

Crystallographic features during martensitic transformation in Ni-Mn-Ga ferromagnetic shape memory alloys

The martensitic transformation crystallography in two Ni ₅₃Mn₂₅Ga₂₂ (at. %) ferromagnetic shape memory alloys (FSMAs) was investigated by means of misorientation calculation and pole figure analysis based on the orientation of the martensitic lamellae obtained from electron backscattered diffraction (EBSD) measurements. In the alloy that was first annealed at 1073K for 4h, and then cooled to 473K at ~4K/min and held for 30min, followed by cooling to room temperature at ~10K/min, there are only two kinds of differently orientated martensitic lamellae with a misorientation angle of ~82° distributed alternatively in each initial austenite grain. There is a compound twinning orientation relationship between the two lamellae. The prevalent orientation relationship between austenite and martensite is Kurdjumov-Sachs (K-S) relationship with (111)_A//(10I)_M, [1-10]_a//[11-1]_m. In the alloy that was annealed at 1173K for 4h followed by furnace cooling, nanoscale twins inside the martensitic lamellae were observed and the orientation relationships both between the nanotwins within one lamella and between the nanotwins in two neighboring lamellae were determined. The results presented in this paper will enrich the crystallographic data of the FSMAs and offer useful information for the development of novel FSMAs with optimal performances.

Structural phase transformations of Mg3N2 at high pressure : experimental and theoretical studies

The structural behavior of Mg₃N₂ has been investigated up to 40.7 GPa at room temperature by means of angle-dispersive X-ray diffraction. A reversible, first-order structural phase transition from the ambient cubic phase (Ia3̅) to a high-pressure monoclinic phase (C2/m) is found to start at ~ 20.6 GPa and complete at ~ 32.5 GPa for the first time. The equation of state determined from our experiments yields bulk moduli of 110.7(2) and 171.5(1) GPa for the cubic and monoclinic phases, respectively, indicating higher incompressibility of the high-pressure phase of Mg₃N₂. First-principles calculations reproduced the phase stability and transition pressure determined in our experiment. In addition, a second phase transition from the monoclinic phase to a hexagonal phase (P3̅m₁) was predicted around 67 GPa for Mg₃N₂. The electronic band structures of three phases of Mg₃N₂ are also calculated and discussed.

Multi-target tracking via space transformations using a single frequency continuous wave radar

This paper investigates the location and velocity estimation problem involving multiple targets using the phase difference and frequency shift of the returned Doppler modulated signal. The minimal receiver configuration that addresses the data association and missing information problem is presented for the case of linear arrays. Non-linearly modeled Doppler radar measurements are used to obtain an accurate estimate of the target dynamics progressively in a linear framework utilizing a recently developed robust state estimation approach.

A typology for business transformations (research in progress)

The term “business transformation” is a buzzword, often used to signify fundamental changes undergone by organisations. Despite numerous works in enterprise transformation, IT-enabled business transformation and organizational transformation, there appears to be a lack of consensus on what actually constitutes a business transformation as opposed to other types of redesign or organisational improvement projects. Consequently, knowledge about which elements of a business system that are impacted by such an endeavour is largely inconsistent, and partially conflicting. We present a business transformation typology that considers 18 attributes pertaining to the transforming organisation and the transformation initiative. To explore our typology, we analysed 10 published case studies and classified them along two dimensions – one ranging from marginal to fundamental changes, and another on internal and external visibility. Our literature review reveals how the terminology has been misused, and we provide some directions to provide more clarity around transformation phenomena in IS research.