Spark plasma sintering the spark-erosion powders of functional alloys

Various shape memory alloys (Ti-Ni-Hf, Ni-Al and Cu-Al-Ni) were elaborated by spark plasma sintering method from the micron, submicron and nano- sized particles prepared by spark-erosion method in cryogenic liquid from preliminary melted master alloys. These alloys are being developed as one of the alternatives for the intermediate temperature applications (100-900oC). Spark plasma sintering method is express method, which provides lower temperature and shorter holding time of sintering. It makes possible to sinter materials from the pre-alloyed powders and eliminate the intensive grains growth and precipitating processes influencing the mechanical and functional properties of functional materials. The effects of processing parameters on the martensitic transformation and microstructure of the sintered compacts were investigated using XRD and SEM study. Temperatures of sintering were chosen according to the assessed data of the decomposition, oxidation and others processes carrying out in material. Although the precipitating processes were usually not completely depressed, the intensive grain growth was also not found in most cases. Most of the microstructure peculiarities of as processed powder were inherited by the sintered material. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2079

The Role of Nano-sized Fraction on Spark Plasma Sintering the Pre-Alloyed Spark-Erosion Powders

Ti-Ni-Hf, Ni-Al and Cu-Al-Ni shape memory materials were produced by spark plasma sintering method from the micron and nano-sized particles prepared by spark-erosion method in cryogenic liquid from preliminary melted master alloys. The effects of spark plasma sintering processing parameters on the martensitic transformation and microstructure of the sintered compacts were investigated using XRD and SEM methods. Although precipitating processes were usually not completely depressed, the intensive grain growth was also not found in most cases. Most of the microstructure peculiarities of as processed powder were inherited by the sintered material. The contradictory role of the nano-sized fraction of powders is discussed: in most case this fraction promotes the rapid sintering but also the oxidation proceses in sintered compacts. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2489

Microstructure Investigation of the Spark Plasma Sintered Cu—Al—Ni Shape Memory Material

Исследована микроструктура компактов Cu—13,0Al—3,9Ni—0,4Ti—0,2Cr масс.%, спечённых плазменно-искровым методом из электроэрозионных порошков, изготовленных из мастер-сплава в жидком аргоне.Досліджено мікроструктуру компактів Cu—13,0Al—3,9Ni—0,4Ti—0,2Cr ваг.% спечених плазмово-іскровим методом із електроерозійних порошків, виготовлених із мастер-стопу в рідкому арґоні.The microstructure of Cu—13.0Al—3.9Ni—0.4Ti—0.2Cr wt.% compacts sintered by spark plasma method from powders prepared by spark-erosion method in liquid argon from master alloy is investigated

Effect of Alloying and Ageing on Parameters of the B2↔R Transition in TiNi-Me Alloys

Specific splitting of the l/3(hkl) reflections along with the B2(CsCl)-matrix reflections at the B2↔IC↔C(R) transition at T≤TRcor was observed. Linear size of the R-phase needle-like domain structure λ1 correlates well in a reverse manner with degree of incommensurability δ1. The CDWs formation with coupling to longitudinal displacement wave is thought to be responsible for the B2↔R phase transition

Effect of Chemical Composition and Heat Treatment on the Shape Memory Parameters in the TiNi-Me Alloys

The TiNi-Me shape memory alloy parameters (namely, phase transformation "strength yield" recoverable strain, reversion stress, material hardness) have been investigated as a function of the chemical composition, heat treatment regimes and deformation condition. These parameters are found to be structurally sensitive ones both to the macroscopic and microscopic structure of the material. Their response to heat treatment regimes is usually non-homogeneous function of the aging temperature and time variation. Effects of doping and secondary particle precipitation are of great importance. Some recommendations for the choice of the SMA chemical composition and final heat treatment regime can be proposed

2D Fourier Analysis and its Application to Study of Scaling Properties and Fractal Dimensions of ε-Martensite Distribution in γ-Matrix of Fe-Mn-Si Alloy

2D Fourier analysis is proposed to obtain quantitative information on the structural amplitudes in reciprocal space for different heterophase systems. An original technique for profound computer processing of optical images transformed into an appropriate digital form is developed. Correlation Fourier analysis is applied to study a spatial distribution of γ → ε martensitic transformation product in Fe-Mn-Si shape memory alloy. An evident spatial self-similarity and scaling behavior is observed, indicating a fractal-like distribution of ε-phase in 7-matrix. The structural factor versus wave number dependence shows three scaling invariant regions with different scaling dimensions and crossover regions between them. A simple fractal model is proposed to interpret experimental results