Zunjie Wei

Effect of sintering neck on compressive mechanical properties of porous titanium

In order to study the role of sintering neck in porous titanium with helical pores, the effect of size and position of sintering neck on compressive mechanical properties of porous titanium single cell was studied by using numerical simulation method. The results show that the compressive mechanical properties of the porous titanium unit cell are determined by the helical pore structure and sintering neck. Contribution coefficient of sintering neck is approximately 3.5 times larger than that of helical pore structure. With the increase of the relative diameter of sintering neck, compressive yield stress and elastic modulus of the cell are constantly increased. The sintering point of C1 is the most important sintering position. Under the same condition, increasing the size of sintering neck at C1 is much effective to the increasing of compressive properties.

Microstructure and nanohardness of Ti-48%Al alloy prepared by rapid solidification under different cooling rates

The influence of cooling rate on the microstructure and nanohardness of the rapidly solidified Ti-48%Al alloys prepared by melt spinning method was studied. The results show that the microstructure of the rapidly solidified ribbons is refined and homogenized compared with that of the conventionally cast mother alloy. With increasing the cooling rate, the grain size decreases greatly. The relationship between the ribbon thickness and the wheel speed was examined, and the effect of the wheel speed on the cooling rate was also studied. It was found that the ribbon thickness decreases inversely with the wheel speed. The nanohardness increases with increasing cooling rate due to the grain size strength.

Interfacial reactions between Ti-1100 alloy and CaO crucible during casting process

Abstract Ti-1100 alloys were melted in a controlled atmospheric induction furnace equipped with a CaO crucible. The microstructure, chemical composition, microhardness and metal–crucible interfacial reactions were systematically investigated. The results demonstrate that the primary solidification microstructure in the as-cast alloys was the typical Widmanstatten structure. The interactions between crucible and molten alloys are attributed to slight chemical dissolution and weak physical erosion. According to the line scanning analysis, the interfacial layer (α-case) thicknesses of Ti-1100 samples in the bottom and side wall are about 18 and 17 μm, respectively, which are slightly lower than those presented from microhardness tests (25 and 20 μm). The formation of α-case was caused by interstitial oxygen atoms. The standard Gibbs energy of reaction CaO(s)=Ca+O for Ti-1100 alloy was also determined. The equilibrium constant and the interaction parameter between calcium and oxygen were obtained as lg K=-3.14 and eCaO = 3.54.

Microstructural characterization of in situ synthesized TiB in cast Ti-1100–0.10B alloy

Abstract The as-cast Ti-1100–0.10B alloy was prepared by a vacuum induction-melting technology. The microstructural characterization of in situ synthesized TiB and the interfacial structure of TiB/Ti matrix were systematically investigated. The results demonstrate that the TiB phase precipitates preferably at the prior β grain boundaries. The TiB phase grows along [010] direction with a typical needle-like morphology. The transversal section of TiB is hexagonal, and the interfaces between TiB and the Ti matrix are clean without precipitation phase. The stacking faults are observed on the (100) plane of the TiB phase, which are ascribed to the locations of boron (B) atoms in the crystal structure of TiB and the lattice mismatch energy between TiB and Ti matrix.

Effects of Sb content on microstructure and mechanical properties of Mg-6Zn-Y-Zr-xSb alloy

Abstract Effects of Sb content on microstructure and mechanical properties of Mg-6Zn-Y-Zr-xSb alloy were investigated by OM, SEM, XRD and mechanical property test. The results indicate that addition of Sb can break continuous network structure into particles in the interdendritic spaces, and with increasing Sb content, the volume fraction of these particles increases. The as-cast microstructure of the alloy with low content of Sb consists of α-Mg, Zn-rich phase, eutectic structure (α-Mg+I-phase) and YSb. With increasing Sb content, Mg3Sb2 and Mg4Zn7 phases appear, while I-phase disappears finally. The ultimate tensile strength and elongation increase first with the increase of Sb content, while the mechanical properties reduce at excessive Sb content.