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The inconsistencies regarding the fundamental correlation between Gd content and slip (twinning) activities of Mg alloys appeal further investigations. However, the traditional slip dislocations analysis by TEM is time-consuming, and that by SEM/EBSD cannot recognize the partial slip modes. These urge a more efficient and comprehensive approach to easily distinguish all potential slip modes occurred concurrently in alloy matrix. Here we report a modified lattice rotation analysis that can distinguish all slip systems and provide statistical results for slip activities in Mg alloy matrix. Using this method, the high ductility of Mg-Gd alloy ascribed to the enhanced non-basal slips, cross-slip, and postponed twinning activities by Gd addition is quantitatively clarified.

Twinning-detwinning (TDT) behavior in a strongly basal-textured Mg-Li alloy during two-step compression (RD)-compression (ND) process was investigated using quasi-in-situ EBSD. TDT behavior and TDT variants selection were statistically discussed with the loading path for the first time. Non-Schmid twinning behavior was observed in the first step compression, owing to the local stress fluctuations by neighboring twins; in contrast, Schmid's law well predicted the detwinning variants selection. This asymmetrical TDT behavior was first investigated to date related with the strong basal texture and loading path. Besides, with the progress of compression, Schmid factors for twinning demonstrated a decreasing tendency; however, those for detwinning during the second step displayed an abnormally increasing trend, fundamentally stemming from prior twinning behavior.

Flowability, particle size distribution and particle inner pore features for powders of Ti-6Al-4V, 316-steel, and Co-29Cr-6Mo alloys produced by plasma rotating electrode process (PREP) at various rotation speeds are analyzed by using scanning electron microscopy (SEM) and synchrotron X-ray computed tomography (CT). The results show that powder flowability is related to particle size distribution, surface morphology and dynamic friction coefficient of the alloy itself. This results in the higher powder flowability at low rotation speed than that at high rotation speed. Average particle size is roughly proportional to the square root of the reciprocal of rotation speed. In addition, particle size has an important effect on the particle porosity and the number faction of hollow powder in coarse powder is obviously larger than that in fine powder. Meanwhile, the alloy composition also plays a key role on porosity due to the various surface tension of alloys.

This work proposes a novel strengthening strategy for HCP alloy by fully utilizing the strengthening roles from texture and dual-precipitates in both basal and prismatic planes. The binary Mg-7Al (at%) alloy fabricated by such a strategy exhibits a superior combination of strength and strain hardening rate in major plastic strain ranges. Unlike conventionally fixed distribution of precipitate on given lattice plane, both basal and prismatic Mg17Al12 precipitates are firstly engineered to co-exist and reinforce Mg alloy. Additionally, this work reports the presence of a new precipitate morphology with a hammer-like geometric configuration for the first time to date. Further application and extension of this novel strengthening strategy to other HCP alloys, like Ti, Zr, are also discussed.

This research was aimed at investigating the high temperature oxidation behavior of Inconel 718 superalloy fabricated by electron beam melting with the building direction of 0&deg, 55&deg, and 90&deg, deviation from the Z axis of cylindrical samples. Columnar &gamma, fcc phase with preferred crystal orientations was found in all specimens. With the temperature ranging from 700 to 1000 &deg, C, the 0&deg, sample, symbolized by the lowest grain boundary density, and largest grain size, reveals the best oxidation performance. It is concluded that the building direction has more impact on the amount of grain boundary density than crystal orientation, which determined the oxidation resistance.

Microstructure and mechanical properties of novel Ni-20Co-12Cr superalloys, with and without Nb addition, were systematically studied during long-term thermal exposure. With increased exposure time, the average diameter of the γ′ precipitates increased in both alloys in succession, this is more obviously observed in alloy containing 1 wt% Nb (1Nb). It is suggested that Nb increased the γ′ coarsening rate by accelerating the diffusion of Al and Nb in γ matrix. In addition, the γ′ phase fraction is increased by about 4% in 1Nb compared to the alloy without Nb (0Nb). The morphology of the γ′ phase changed from near-spherical to cuboidal shape during exposure in both alloys. Due to the increased γ/γ′ lattice misfit by Nb addition, 1Nb alloy showed an earlier tendency of shape change. Vickers hardness results revealed that the overall hardness decreased with the exposure time because the size increment of the γ′ precipitate weakened the precipitates strengthening and Orowan strengthening.

The roles of Co on the strain-hardening behavior, deformation mechanism, mechanical properties and facture mode of Ni–16Cr–11Mo–2Cu alloy were thoroughly investigated using tensile tests, SEM, EBSD, TEM and HRTEM. Two alloys with a similar sole FCC-γ phase constitution, near grain size only except the composition difference of 30 wt% Co were fabricated in purpose. Co addition can overcome the strength-ductility trade-off by enhancing the strain-hardening rate and capacity. The deformation behavior evolves from slip-dominated to SFs-dominated after Co addition, due to significant decrease of stacking fault energy, the critical stresses for both SFs and twinning by Co addition. In terms of facture mode, dimples-dominated ductile fracture is transformed to quasi-cleavage fracture composed of cleavage planes and dimples after Co addition. This is probably owing to the special role of SFs on intensifying stress/strain incompatibility phenomenon in polycrystalline alloys.