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We report the microstructure and mechanical properties of Ti-6Al-4VELI (extra low interstitial) alloy parts fabricated with three diameter distributions of Ti-6Al-4VELI spherical powders by hot isostatic pressing (HIP), which were manufactured via plasma rotating electrode processing (PREP). The powders were canned and pressed at temperatures 940 °C and pressure 120 MPa. α+β mixed phases in the specimens were observed through Optical Microscope (OM), Scanning Electron Microscopy (SEM) and energy dispersive spectroscopy (EDS) methods. The results show the microstructures of specimens are found to be strongly dependent on the different distributions of powders. The samples formed from fine powders (45∼100 μm) shows better microstructure properties than those formed from medium powders (100∼150 μm) and coarse powders (150∼250 μm). In addition, the billets formed from fine powders exhibit higher tensile strength and ductility than those formed via medium powders and coarse powders. These results are attributed to the initial microstructures of HIP samples, as confirmed by evaluating their fracture features.

The evolution of primary α phase morphology and mechanical properties of a novel high-strength titanium alloy during heat treatment were investigated. The results show that the primary α phases exhibit a globular growth feature on the basis of the equiaxed α phases under double solution treatment at air cooling process of α/β zone. But abnormal growth of primary α grains occurs in the 0.5 °C/min furnace cooling process except that some primary α remains spherical growth, i.e. the other part of α grains evolve into similar “fork” shaped dendritic growth rather than keeping nearly spherical growth trend. The novel titanium alloy has attractive combinations of strength and ductility (≈1300MPa of ultimate strength with 10.5% of elongation) owing to the microstructures of equiaxed or thin billet-like primary α phase and fine needle-like secondary α phase after α/β solution treatment followed by air cooling plus aging. After α/β solution treatment followed by furnace cooling to low temperature and then aging heat treatment, the new type alloy has an excellent fracture toughness (≥80 MPa·m1/2), and the elongation and reduction of area remain at about 19% and 45%, respectively, and its corresponding tensile strength is maintained at about 1000 MPa. It can be assumed that the alloy may be a usable structural material.

A new high strength titanium alloy containing elements Cr, Fe, Mo, W and Al was designed in order to achieve an excellent combination of ultra-high strength and good fracture toughness. Both the α/β and β heat treatment were introduced to study the effect of microstructure on mechanical properties of the alloy. The result shows that the alloy with α/β solution plus aging treatment is composed of mixture microstructures including a few equiaxed or short billet-like primary α phase and fine lamellar secondary α phase. The alloy has an excellent combination of ultra-high strength and good fracture toughness. The corresponding tensile strength exceeds 1400 MPa and fracture toughnesses KIC is up to 50.7 MPa-m1/2. Compared with the alloy after α/β heat treatment, the alloy with β region heat treatment presents representative Widmanstatten structure which has higher fracture toughnesses and lower strengths than the bimodal microstructure.

Tungsten–molybdenite (W–Mo) polymetallic mineralization are intensely developed in the western section of the North Qilian Orogen (NW China), represented by the Xiaoliugou and Ta’ergou ore fields. In this study, fluid inclusion microthermometric and S–Pb H O Nd isotopic analyses were conducted on the W–Mo ores to shed insights into the genesis of the mineralization belt. The ore fields are characterized by abundant liquid-vapor two-phase inclusions which have medium–high temperature-salinity (200–320 °C and 4–10 wt% NaCl equiv.). The consistent δ18OV-SMOW (7.7‰ to 13.1‰) and δ2HV-SMOW (−88.1‰ to −49.4‰) values of quartz and muscovite indicate that the ore-forming fluid originated from granitic intrusion but mixed with meteoric water. Typical δ34S values of their sulfide ores range from 6 to 18‰, and the ore-related granites (206Pb/204Pb = 18.18–26.61, 207Pb/204Pb = 15.51–16.02, 208Pb/204Pb = 37.60–39.77) and sulfides (206Pb/204Pb = 17.97–20.06, 207Pb/204Pb = 15.42–16.64, 208Pb/204Pb = 37.39–41.06) have variable Pb/Pb ratios, indicating both magmatic rocks and meta-sedimentary rocks contributed to the mineralization. The negative Nd values (eNd(t) = −9.0 to −3.2) and old two-stage Nd model ages (TDM2 = 1517 to 1901 Ma) of the scheelites suggest that the ore-forming materials may have been derived from old crust together with the granitic magma. An isochron age of 422 ± 42 Ma (initial 143Nd/144Nd = 0.511701 ± 0.000046) has been yielded by the scheelite Sm-Nd dating from the Ta’ergou ore field, implying the 450–420 Ma magmatic–hydrothermal event resulted in the intense W–Mo mineralization in the North Qilian, especially in the western section of this orogen. Consequently, we propose a multi-metal coupled mineralization model to illustrate the mineralization process of the ore fields, which involving the formation of ore source beds (wall-rocks) in Proterozoic and the intrusion of granites in Early Paleozoic. This research highlights the use of multiple isotopic methods in revealing complex fluid evolutionary process of large-scale W–Mo deposits.