Microstructure and high-temperature mechanical properties of near net shaped Ti−45Al−7Nb−0.3W alloy by hot isostatic pressing process

Near net shaped Ti−45Al−7Nb−0.3W alloy(at.%)parts were manufactured by hot isostatic pressing(HIP).The microstructure and high-temperature mechanical properties of the alloy were investigated by X-ray diffractometry(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that at a temperature of 700℃,the peak yield stress(YS)and ultimate tensile stress(UTS)of alloy are 534 and 575 MPa,respectively,and the alloy shows satisfactory comprehensive mechanical properties at 850℃.The alloy exhibits superplastic characteristics at 1000℃ with an initial strain rate of 5×10^−5 s^−1.When the tensile temperature is below 750℃,the deformation mechanisms are dislocation movements and mechanical twinning.Increasing the tensile temperature above 800℃,grain boundary sliding and grain rotation occur more frequently due to the accumulation of dislocations at grain boundary.

Influence of Alloying Element Addition on Cu–Al–Ni High-Temperature Shape Memory Alloy without Second Phase Formation

In this study, the effects of rare earth Gd and Fe elements on the microstructure, the mechanical properties and the shape memory effect of Cu-11.9Al-3.8Ni high-temperature shape memory alloy were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction and compression test. The microstructure observation results showed that both Cu-11.9Al-3.8Ni-0.2Gd and Cu-11.9Al-3.8Ni-2.0Fe-0.2Gd alloys displayed the fine grain and single- phase fll1 martensite, and their grain size was about several hundred microns, one order of the magnitude smaller than that of Cu-11.9Al-3.8Ni alloy. The compression test results proved that the mechanical properties of Cu-11.9Al-3.8Ni alloy were dramatically improved by alloying element additions due to grain refinement and solid solution strengthening, and the compressive fracture strains of Cu-11.9Al-3.8Ni-0.2Gd and Cu-ll.9Al-3.8Ni-2.0Fe-0.2Gd were 12.0% and 17.8%, respectively. When the pre-straln was 10%, the reversible strains of 5.4% and 5.9% were obtained for Cu-11.9Al-3.8Ni- 0.2Gd and Cu-ll.9Al-3.SNi-2.0Fe-0.2Gd alloys after being heated to 500 ℃ for 1 rain, and the obvious two-way shape memory effect was also observed.

PREPARATION OF TiNi SHAPE MEMORY ALLOY POROSINT BY SHS

TiNi shape memory alloy porosint, a promising artificial bone material, was prepared by self propagating high temperature synthesis method. It is found that the key technical parameter affecting the porosity, the shape and distribution of the bores in the synthesized product is the pre heating temperature of green compact. While the pre heating temperature varies between 523 K and 673 K, the TiNi shape memory alloy porosint with wholly homogeneously distributing bores will be gained. The porosity of the porosint is 70% when the pre heating temperature is near 673 K, which is maximal under different pre heating temperatures. The compressive strength of TiNi SMA porosint with a porosity of 70% manufactured by SHS is up to 100 MPa and the percentage recovered is 92%.

Combined experimental and theoretical study on the effect of Nb content on martensitic transformation of NbRu shape memory alloys

The effect of Nb content on the martensitic transformation of NbRu high-temperature shape memory alloys is investigated by experiments and first-principles calculations. We calculate the lattice parameters, density of states, charge density, and heats of formation of Nb50＋xRu50-x βphase. The results show that an increase in Nb content increases the stability of Nbso＋xRu50-x β phase, leading to a significant decrease of the β to β ′martensitic transformation temperature. In addition, the mechanism of the effects of Nb content on phase stability and martensitic transformation temperature is studied on the basis of electronic structure.

高温形状记忆合金研究进展

本文以ＴｉＮｉ基、ＮｉＡｌ基、Ｃｕ基以及ＴｉＰｄ基高温形状记忆合金为主，简要综述了高温形状记忆合金的研究现状及其发展前景。

THE ACCURATE MOLECULAR FORMULA OF "Ti_(11)Ni_(14)" PHASE

From the orientation relationship between 'Ti11Ni14' phase and matrix phase (B2),the accurate molecular formula of 'Ti11N14' phase has been derived in this paper. The results also show that the rhombohedral unit cell of the 'Ti11Ni14' phase includes six Ti atoms, seven Ni atoms and one vacancy, belonging to space group R3.