Baohong Zhang

Al/Fe bimetals prepared by a compound casting method, combining the excellent properties of both the Al alloy and the ductile cast iron, exhibit great potential for application in achieving engine weight reduction. However, the problem of insufficient interfacial bonding ability because of the difference in thermophysical properties of Al and Fe is particularly prominent. Therefore, in this work, the electrodeposited Cu coating on the surface of the Fe matrix was used as the interlayer of Al/Fe bimetal fabricated by coupling hot-dipping with compound casting to solve the above problem. The effect of Cu interlayer thickness on the interfacial microstructure and shear strength of bimetal was investigated. The experimental results showed that the shear strength up to 77.65 MPa in regard to Al/Fe bimetal with a 5 μm Cu interlayer was obtained. No Cu element was detected at the interface of bimetal regardless of the thickness of the Cu interlayer. The diffusion behavior of the Cu atom at the interface and the influence of the Cu layer at the atomic scale on diffusion reaction and the Al/Fe interface were further revealed by combining first-principle and molecular dynamics calculations. The simulation results revealed that the Cu layer gradually dissolved into an Al alloy at 750 °C, thereby promoting the diffusion reaction of the Al/Fe interface. Meanwhile, the protective role of the Cu layer against oxidation on the surface of the Fe matrix was confirmed. As a result, the interfacial bonding performance was enhanced when the Cu interlayer was introduced.

Roll forming can improve the material utilization rate and production efficiency of cups with a curved rotary profile, but there is no basis for the determination of forming limit. The DEFORM-3D software was used to simulate the roll forming of cups. The influence of the billet wall thickness and bottom thickness, coefficient of friction, radius of roller, and the fillet radius of the punch on the forming limit was studied, and the damage value and velocity vector were analyzed. The results showed that the forming limit of the billet’s wall thickness in roll forming for a cup is about 62%. With the increase of the ratio of the formed cup’s wall thickness to the billet’s bottom thickness, the forming limit of wall thickness will be slightly reduced. A larger radius of roller, fillet radius of punch, and friction coefficient between punch and billet and a smaller friction coefficient between roller and billet are good for decreasing the damage value and improving the roll-forming limit. According to the numerical simulation results, the roll-forming limit diagram of cups is established, and the accuracy of the forming limit diagram is verified by experiments.

Titanium diboride has a series of excellent physical and chemical properties, high melting point and hardness, good thermal stability and oxidation resistance. As an excellent hard phase, titanium diboride is used in new materials such as composite materials and cermet. It has a wide prospect in the application of high-temperature ceramics. In this paper, the research status, performance structure, preparation method and application of titanium boride high-temperature ceramics are analyzed and summarized from the overall point of view, and the main problems faced by titanium boride at present are also discussed. Finally, the future research direction of titanium boride high temperature ceramics is discussed.

Rotating backward extrusion (RBE) is one of severe plastic deformation (SPD) methods used to produce cylindrical components with a very large strain by a single pass. In this study, the microstructure and texture evolution in the different regions of Mg-12Gd-4Y-2Zn-0.5Zr (wt.%) alloys via RBE process were investigated by using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron back-scatter diffraction (EBSD). The results showed that the cup-shaped sample formed by RBE process exhibited typical gradient microstructure expanding from its inner wall to outer wall along the radial direction (RD). The average grain size of the RBEed sample decreased when the radius decreased from the edge region to the center region along the RD, which was attributed to the different strains and strain rates in the different regions. It also could be observed that the center region showed highest deformation and the edge region exhibited the lowest deformation in the RBEed sample along the RD. In addition, the grain refinement mechanisms of the experimental alloy containing long-period stacking ordered (LPSO) phases after RBE with 100 N were continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX) and particle stimulated nucleation (PSN).

Through controlling from the source, TC4 titanium alloy profile ingot heating process surface protection technology and extrusion lubrication process, extrusion die design and manufacturing, profile straightening process, finished product heat treatment process and profile hot bending forming and other key processes have been studied in depth. Technical improvements and quality assurance measures are proposed. The surface quality, shape, size and mechanical properties of the titanium alloy profile meet the requirements of the use of TC4 titanium alloy profile parts for a certain type of launch vehicle. Ensure that the TC4 titanium alloy profile acceptance inspection process is operable. The manufacturing cost of the titanium alloy outer stringer of the launch vehicle is reduced. The quality level and reliability of TC4 titanium alloy outer stringers have been improved.

In this paper, a novel roll forming (RF) process is introduced. A kind of 120-mm projectile body with curved rotary profile is formed by the RF process. The RF process is compared with the traditional process of machine using the billet of draw. Based on the results, it can be concluded that the weight of billet reduces 28% by the presented process comparing with the traditional process and the reducing amount will increase with the increasing of the length of curved rotary profile. The presented process can use traditional draw press and has the same forming productivity. It also has the merits of lower forming force and machine time. The die of the present process is more complex and the manufacturing cost is higher than that of the traditional draw, but the die life of the present process is higher.

The effect of friction coefficient, reduction of thickness, forming speed, roller diameter on the coefficient of forward slip at the rim of the roller during cup roll forming was studied by numerical simulation. The results show that during roll pre-forming, the friction coefficient and forming speed have little effect on the coefficient of forward slip, and the reduction of thickness and the diameter of the roller have a greater influence on the coefficient of forward slip; as the reduction of thickness increases, the coefficient of forward slip increases; as the roller diameter increases, the coefficient of forward slip increases first and then decreases. The coefficient of forward slip during the roll pre-forming of cup is much larger than that of roll forging. During roll shaping, the process parameters have little effect on the coefficient of forward slip and its value is close to zero, that is, the axial length of the roll shaped part is almost equal to the arc length of the roller rim. The accuracy of numerical simulation is verified by experiments, and the error between the numerical simulation and experiment is less than 1%.

Based on the principle of plastic forming, the metal flow of cup with variable wall thickness during roll forming is analyzed, and the formula of its coefficient of forward slip is derived. By comparing with the numerical simulation results, the correction formula of the coefficient of forward slip at the rim of roller is obtained. The correction formula is verified by experiment. The results show that the error between the theoretical and experimental value is 4.5%, and the agreement between them is good. This research provides a basis for the design of the roller groove for the roll forming of cup with variable wall thickness.