Wenchang Liu

Bio: Wenchang Liu is an academic researcher from Yanshan University. The author has contributed to research in topics: Strain rate & Dynamic recrystallization. The author has an hindex of 7, co-authored 13 publications receiving 148 citations.

Effect of cold rolling on the precipitation behavior of δ phase in INCONEL 718

Abstract: Systematic research has been undertaken on the effect of cold rolling on the precipitation kinetics of δ phase in INCONEL 718. Above 910 °C, cold rolling promotes the precipitation of δ phase. Below 910 °C, the precipitation of δ phase is still preceded by the γ″ precipitation in cold-rolled INCONEL 718. Cold rolling promotes not only the precipitation of γ″ phase but also the γ″ → δ transformation. The relationship between the weight percentage of δ phase and aging time follows the Avrami equation. Below 910 °C, as cold rolling reduction and temperature increase, the time exponent (n) decreases, whereas the rate of δ precipitation increases. The apparent activation energy of δ precipitation varies in the range of 1113 to 577 kJ/mol for 25 to 65% cold-rolled INCONEL 718 and decreases as cold rolling reduction increases. Precipitation-time-temperature (PTT) diagrams have been determined for the four cold-rolled INCONEL 718. The noses of the PTT curves are located at about 910 °C. These curves are shifted significantly to longer times as cold rolling reductions decrease.

Microstructure, texture and mechanical properties of Al/Al laminated composites fabricated by hot rolling

Abstract: AA 1060/3003/1060 laminated composites were fabricated by hot-roll bonding. The effect of rolling temperature on the microstructure, texture and mechanical properties of AA 1060/3003/1060 laminated composites was investigated. The results show that the development of microstructure and texture through the thickness of Al layers was inhomogeneous in the Al/Al laminated composites. Initial grains were elongated along the direction of about 15° to the RD in the region near the surface layer of AA 1060 aluminum alloy, and the incline angle gradually decreased as the measured position moved towards the interface of 1060/3003 from the surface layer. The rolling texture of 1060 layer consisted of the r-cube and γ-fiber shear textures and the remaining cube component. The r-cube shear texture weakened gradually as the measured position moved towards the interface of 1060/3003 from the surface layer, whereas the center layer of AA 1060 aluminum alloy had the strongest γ-fiber shear texture. The interface layer of AA 3003 aluminum alloy had a completely different texture from the center layer. For the Al/Al laminated composites, the YS and UTS first increased to a maximum value at about 200 °C and then decreased with increasing rolling temperature.

Recrystallization behavior of cold-rolled Zr 702

Abstract: Using the hardness test, we determined the recrystallization kinetics of cold-rolled Zr 702. The rate of the recrystallization process increased with increasing annealing temperature and rolling reduction. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) exponent obtained was less than 1, which also increased with increasing annealing temperature and rolling reduction. The activation energies for the recrystallization of the 38.9% and 71.0% cold-rolled sheets were 232 kJ/mol and 251 kJ/mol, respectively.

On the Phenomenon of Stress Drop During Hot Deformation of ZrTiAlV Alloy

Abstract: Hot deformation behaviors of 47Zr-45Ti-5Al-3V alloys with different grain sizes were investigated by compression tests The flow curves exhibited a pronounced stress drop at the very beginning of deformation The magnitude of the stress drop increased with the decreasing deformation temperature and the increasing strain rate The sudden stress drop may be associated with the disappearance of mobile dislocations in the grain boundaries Larger initial grain size increased the flow stress, promoted the stress drop, and enhanced the activation energy of deformation

Effect of Rolling Reduction on the P \left\{ {011} \right\}\left\langle {455} \right\rangle Recrystallization Texture in a Supersaturated Al-Mn-Mg Alloy

Abstract: The hot band of a continuous cast (CC) Al-Mn-Mg alloy was cold rolled to different reductions ranging from 0 to 90 pct and then annealed at 482 °C for 3 hours. The effect of rolling reduction on the P recrystallization texture was investigated by X-ray diffraction. The results show that the recrystallization texture of the hot band is characterized by weak P orientation and 22.5 deg normal direction (ND) rotated cube orientation. The strength of the P texture increases with increasing rolling reduction. After 90 pct cold rolling, the recrystallization texture of the cold-rolled sheet is dominated by a strong P component.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Delta phase precipitation in Inconel 718

Abstract: The precipitation and dissolution kinetics of the δ-phase were studied in three wrought versions and one spray-formed (SF) version of the nickel alloy, Inconel 718. The precipitation in the spray-formed version and one wrought version was followed during isothermal ageing for up to 100 h between 700 and 1000 °C. The δ-phase precipitates in the form of nonuniformly distributed thin platelets and an alternative method of measuring volume fraction of this precipitate morphology is proposed. At and above 800 °C, the precipitation was measured quantitatively in terms of the volume fraction and platelet thickness distribution. The maximum rate of precipitation occurred at approximately 900 °C. The solvus temperature lay between 1005 and 1015 °C for Nb contents of 5.06 and 5.41 wt.%, respectively. A study was made of the dissolution of the δ-phase in all four alloys using isochronal treatments and this confirmed the above solvus temperature range. The effect of δ-phase and its dissolution on the grain growth of the alloys was also determined.

Superior creep strength of a nickel-based superalloy produced by selective laser melting

Abstract: The creep properties of a polycrystalline nickel-based superalloy produced via selective laser melting were investigated in this study. All heat treatment conditions of the additively manufactured material show superior creep strength compared to conventional cast and wrought material. The process leads to a microstructure with fine subgrains. In comparison to conventional wrought material no Niobium rich δ phase is necessary to control the grain size and thus more Niobium is available for precipitation hardening and solid solution strengthening resulting in improved creep strength.

Effect of Cold Rolling and Heat Treatment on the Mechanical Properties of GH4169 Alloy Sheet at Room Temperature

Abstract: The mechanical properties of GH4169 alloy sheet after cold rolling (at 0%, 10%, 30%, 50% and 70%) and solid solution were investigated. The textures and Taylor factors were characterized using electron backscattering diffraction (EBSD). The fractions of δ phase were measured by X-ray diffraction. The contributions of δ phase, grain size, texture, and work hardening on the mechanical properties were also discussed. The results showed increases in the yield strength (YS) (0.2%) as well as the ultimate tensile strength (UTS) of GH4169 superalloy sheet after cold rolling, when rolling reduction was increased. In contrast, following solid solution treatment, YS and UTS were increased then subsequently decreased. The changes of yield strength of GH4169 superalloy were attributed to the texture and work hardening, followed by the grain refinement and precipitation of δ phase. When the rolling reduction was below 30%, the influence of δ phase was greater than grain refinement and when the rolling reduction was larger than 50%, the controversial results occur. The precipitation of δ phase promoted the improvement of yield strength, the relationship between the fraction of δ phase and improved yield strength satisfactory fit to the following equation: σδ = 15.9Wδ + 59.7.

Effects of cold rolling on the precipitation kinetics and the morphology evolution of intermediate phases in Inconel 718 alloy

Abstract: Isochronal DSC measurements of various degrees cold-rolled Inconel 718 alloy samples were implemented to investigate the effect of cold rolling on the precipitation kinetics of intermediate phases in Inconel 718 alloy. The result shows that the values of the onset temperature ( T O n s e t 1 ) , the peak temperature ( T P e a k 1 ) and the end temperature ( T E n d 1 ) of γ″-phase precipitation decrease as the degree of cold rolling increases. In contrast, all values of the onset temperature ( T O n s e t 2 ) , the peak temperature ( T P e a k 2 ) and the end temperature ( T E n d 2 ) of δ-phase precipitation first increase and then decrease with the degree of cold rolling increasing as a consequence of a combined effect of lack of Nb atoms and recrystallization. Two sets of isothermal aging experiments were also carried out to study the effect of cold rolling on the morphology evolution of γ″-phase and δ-phase in Inconel 718 alloy. It is found that cold rolling promotes γ″→δ transformation and the morphology of γ″-phase turns more globular as the degree of cold rolling increases for the cold-rolled Inconel 718 alloy samples with isothermal aging at 800 °C for 8 h (procedure A). Moreover, for the cold-rolled Inconel 718 alloy samples with isothermal aging at 950 °C for 6 h (procedure B), cold rolling facilitates δ-phase precipitation and the δ-phase particles gradually sphericalized with increase in the degree of cold rolling.