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

The martensitic transformation crystallography in two Ni ₅₃Mn₂₅Ga<sub>22 (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.

A GA-PSO layered encoding evolutionary approach to 0/1 knapsack optimization

This paper presents a layered encoding cascade evolutionary approach to solve a 0/1 knapsack optimization problem. A layered encoding structure is proposed and developed based on the schema theorem and the concepts of cascade correlation and multi-population evolutionary algorithms. Genetic algorithm (GA) and particle swarm optimization (PSO) are combined with the proposed layered encoding structure to form a generic optimization model denoted as LGAPSO. In order to enhance the finding of both local and global optimum in the evolutionary search, the model adopts hill climbing evaluation criteria, feature of strength Pareto evolutionary approach (SPEA) as well as nondominated spread lengthen criteria. Four different sizes benchmark knapsack problems are studied using the proposed LGAPSO model. The performance of LGAPSO is compared to that of the ordinary multi-objective optimizers such as VEGA, NSGA, NPGA and SPEA. The proposed LGAPSO model is shown to be efficient in improving the search of knapsack’s optimum, capable of gaining better Pareto trade-off front.

Determination of crystal structure and crystallographic characteristics in Ni-Mn-Ga ferromagnetic shape memory alloys

Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) have received great attention during the past decade due to their giant magnetic shape memory effect and fast dynamic response. The crystal structure and crystallographic features of two Ni-Mn-Ga alloys were precisely determined in this study. Neutron diffraction measurements show that Ni48Mn30Ga22 has a Heusler austenitic structure at room temperature; its crystal structure changes into a seven-layered martensitic structure when cooled to 243K. Ni53Mn25Ga22 has an I4/mmm martensitic structure at room temperature. Electron backscattered diffraction (EBSD) analyses reveal that there are only two martensitic variants with a misorientation of ~82° around <110> axis in each initial austenite grain in Ni53Mn25Ga22. The investigation on crystal structure and crystallographic features will shed light on the development of high-performance FSMAs with optimal properties.

Perceptions of engineering from female secondary college students in regional Victoria

Survey and focus group interviews with female students in regional Victoria resulted in identification of four perceived barriers that influence them to exclude engineering as a career choice. These barriers were identified as a lack of interest in the perceived image, a lack of knowledge, a traditionally maledominated industry, and limited recognisable role models. This paper reports on what Year 10 females are saying about the barriers and, consequently, how engineering can be promoted to overcome these barriers.

Quantification of sensitization in AA5083-H131 via imaging Ga-embrittled fracture surfaces

Sensitization of 5xxx series Al alloys involving precipitation of β phase (Mg2Al3) at grain boundaries was studied for different exposure times at 100°C upon AA5083-H131 (UNS A95083). In this work, we reveal that fracture surfaces prepared by liquid gallium embrittlement can yield a quantification of grain boundary β phase with significant statistics on β phase size and spacing. This information is a necessary first step toward development of quantitative damage models to describe inter-granular corrosion (IGC) and stress corrosion (IGSCC).

An update of Murrayan needs: A pilot study among American college students

Much research work on motives has been based on the taxonomy of psychogenic needs originally proposed by Murray and his colleagues in 1938. However, many of these needs have received little attention, and some of them may be less relevant now than they were 70 years ago. Two studies were conducted to investigate current motives. In Study 1, we used the Striving Assessment to elicit the personal strivings of 255 undergraduate university students. Murray’s taxonomy was unable to account for 50% of the 2,937 strivings. These strivings were thematically groups into 11 new categories and combined with 7 Murrayan needs to form the Comprehensive Motivation Coding System (CMCS). In Study 2, Thematic Apperception Test (TAT) stories produced by 143 undergraduate student participants were coded by these two systems. Murray’s system was unable to fully account for 42% of motives identified in the TAT stories, but the CMCS was able to account for 89%. These findings suggest that Murrayan needs may not adequately describe contemporary motivations and that the CMCS has the potential to do so. However, due to the limited demographics of our sample, further investigations are needed.