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β-NiAl alloys represent protential structural materials for use at elevated temperatures because of high melting point, low density, and resistance to oxidation and high temperature deformation. NiAl alloys were prepared by powder metallurgy method using hot isostatic pressing and hot pressing techniques. This investigation focused on studying the transformation and deformation behavior of martensite in Ni-Al alloys produced by the powder metallurgy method for possible elevated temperature shape memory applications. The transformation behavior was investigated by electrical resistivity and dilatorneter measurements, and found to be thermoelastic. There is good agreement between the transformation temperaturca determined by dilatometer and electrical resistivity methods. Compression testing was performed to observe the deformation behavior of martensite. Detwinnig occurring from the external compressive stress is the main deformation mode for the NiAl martensite. Quantitative tests to determine the shape recovery were performed on compressed samples by measuring the dilation as a function of temperature after plastic deformation.

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The high temperature deformation behaviors of the V-microalloyed steel were studied by hot torsion test at temperatures from 900 to 1050℃ and in the range of strain rate from 2.0 sec^(-1) to 2.0×10^(-2) sec^(-1). Within the experimental range, this steel exhibited typical dynamic recrystallization shapes of the flow curve. The dynamic recrystallization behaviors were analyzed with changing of deformation conditions from single to multiple peak deformation, and the metallographic observations on the two types flow curves revealed that the single peak flow curves were associated with grains refinement and the multiple peak flow curves were associated with grains coarsening. The sizes of the dynamically recrystallized grains were also measured, and they were able to be parameter as a function of the Zener-Hollomon presented, Z without exhibiting any dependence on the initial grain sizes. The constitutive equation for hot deformation of this steel, relating the flow stresses to the strain rate and temperature, could be described by power law, ε´= Aσ^n´_p exp(-Q/RT).

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Quasicrystalline and quasicrystal-related crystalline phases in rapidly solidified Al-5, l0wt Fe alloys have been investigated in the present study. Detailed electron diffraction analysis shows that two types of quasicrystalline phases exist in rapidly solidified Al-5, 10wt % Fe alloys:1)randomly oriented ㎚ scale fine particle clusters and 2) Al_mFe related quasicrystalline phase having similar diffraction characteristics to Al_mFe crystalline phase. Detailed diffraction analysis also shows that Al_mFe crystal structure is quite similar to Al-Fe quasicrystal structure based on the comparison of diffraction peak positions and intensities.

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The microstucture and mechanical properties of mechanically alloyed Al-Ti alloys were investigated in order to evaluate the relation between the role of dispersoids and their high temperature properties. The MA Al-Ti specimens with the density above 98 % of theoretical one were obtained by hot consolidation i. e., hot pressing or extrusion. The MA Al-Ti alloys have shown the excellent elevated tensile strength up to 350℃ and good thermal stability at 460℃ even after annealing of 100 hours. TEM analysis has revealed the presence of Al₃Ti aluminides with the size of 50-300㎚. The dispersoids of Al_4C₃ carbide and Al₂O₃ oxide were also found in the aluminum matrix. The effects of dispersoid and grain size on the strengthening mechanisms seem to be dominant for the high temperature properties of MA Al-Ti alloys.

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Transformation temperature of martensite to austenite in Fe-15%Mn-5%Cr-5%Co-X%Si shape memory alloy was investigated using thermomechanical analyzer. The transformation temperature (A_(89)A_f) of the thermal ε martensite to the austenite showed constant value regardless of increasing the silicon content. However, the transformation temperature of ε martensite to austenite in the specimen deformed 3 pct in length was increased with increasing the silicon content, and it was higher than that of the undeformed specimen. The stress-induced α` martensites were formed in the α` martensite plates. The reversal transformation temperature of the αmartensite was increased with increasing the silicon content, and it was higher than that of the εmartensite in all silicon contents. It was considered that the α` martensite depressed the reversal martensite reaction in the deformed specimen.

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