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In this study, a new hot-isostatic-pressing process was proposed, combining with the thermo-hydrogen-treatment process. Effects of hydrogen-atoms on the surface-oxide-film and the compaction-temperature of Ti-47Al-2Cr-2Nb pre-alloyed powders were investigated during hot-isostatic-pressing. Results show that the surface-oxide-film of powders of thermo-hydrogen-treatment can be effectively removed. For samples prepared by the new hot-isostatic-pressing process, the oxygen content decreased by 130 ppm and the compaction-temperature reduced by 50–100 °C, comparing with samples prepared by the traditional hot-isostatic-pressing process. After high-temperature vacuum annealing, the compressive fracture strength and ratio of samples prepared by the new hot-isostatic-pressing process is as high as 2830 MPa and 34.5%.

This paper investigated the relationship between crystallographic-orientation and micro-cracks of Ti-47Al-2Cr-2Nb alloy. Results show that the crystallographic-orientation is adverse in the nearly γ microstructure and becomes advantageous in the fully lamellar microstructure. Therefore, micro-cracks largely generate in the nearly γ microstructure and much decrease in the fully lamellar microstructure.

The formation of B2 phase was adjusted via various hot isostatic pressing processes in Ti-47Al-2Cr-2Nb alloy. The microstructure evolution and a new mechanism of B2 phase on room temperature mechanical properties was investigated by BSE, EBSD and TEM in detail. The result shows that the formation of B2 phase leads to Cr element content decrease in γ matrix phase, which results in lattice parameter increase, namely the c/a ratio of γ matrix phase. Finally, at room temperature the mechanical properties of Ti-47Al-2Cr-2Nb alloy deteriorates.

To elucidate changes in the density and substructure of dislocations during tempering of lath martensite steel, a convolutional multiple whole-profile fitting method was applied to in situ neutron diffraction profiles. With increasing tempering temperature, the dislocation density scarcely changed in the beginning and then decreased at temperatures above 473 K, whereas the dislocation arrangement drastically changed at temperatures above 673 K. The strength of the steel is speculated to depend on the density and arrangement of dislocations.

Microstructures and mechanical properties of 0.2C–5Mn steel processed under different heat treatment conditions were examined by scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was found that high temperature austenization (above Ac3) resulted in a full martensite structure after quenching, which gradually transformed into the ferrite/austenite duplex structure during the following annealing process. However, austenization in the intercritical region (between Ac1 and Ac3) gave a duplex structure after quenching, which was nearly not affected by followed annealing process. The ultrahigh strength ∼1000 MPa and total elongation ∼40% were only obtained in the specimens with 6 h annealing at 650 °C under both heat treatment conditions. However, the excellent mechanical properties could be obtained in the intercritically austenitized samples with only 10 min annealing at 650 °C. Based on the analysis on the relationship between microstructure and mechanical properties, it was found that the total elongation was strongly dependent on the austenite fraction, which was ascribed to the phase transformation induced plasticity of the large volume fraction of austenite. Otherwise, the dependence of the yield stress on the austenite grain size accords with Hall-Petch equation, which implies that the austenite is soft phase. It was concluded that 10 min annealing at 650 °C was enough to obtain a large volume fraction of austenite (∼30%) in 0.2C–5Mn steel when the specimens were austenitized at 675 °C.