Rong De Li

Study of Ageing Treatment on Spray Forming Al-Zn-Mg-Cu Alloy

The Al-Zn-Mg-Cu (7A04) alloys were prepared by using the method of spraying forming and the hot extrusion. The changes of microstructure and mechanical properties of the spray deposited Al-Zn-Mg-Cu alloy underwent ageing, regression and reageing treatment (RRA) was studied by scanning electron microscopy, X-ray diffraction and other methods. The results show that the tensile strength of the alloy aged at 120°C for 24 hours can reach the peak value (760MPa), but the elongation is only 4.8 percent. The toughness of the alloy regression treated at 160°C for 2 hours can increase to 9.0 percent, but its tensile strength decreases greatly (680MPa). The reaging treatment at 120°C can make the tensile strength up to 740MPa, while the elongation which is 8.2 percent still keeps a higher level.

Effect of Aging Treatments on Microstructure and Exfoliation Corrosion Behavior of Spray Forming 7075 Alloy

Mechanical properties, microstructure and exfoliation corrosion (EXCO) behavior of spraying forming 7075 alloy underwent retrogression and re-aging (RRA) were studied by tensile test, transmission electron microscopy and EXCO test, and compared with those of T6 peak aging and T73 overaging treatments. The results show that after T6 treatment, abundance transgranular dispersive η phases make tensile strength of the alloy reach 760MPa, elongation and EXCO rating are only 4.8% and ED respectively by dint of continuous η phases at grain boundaries and narrow precipitate free zones (PFZ). After T73 treatment, interrupted η phases at grain boundaries and wide PFZ can improve elongation and EXCO resistance, but depressed volume fraction of coarsening transgranular η phases reduce tensile strength to 676MPa. After RRA treatment (120°C/24h + 200°C/10min + 120°C/24h), abundance transgranular dispersive η phases separate out again, η phases at grain boundaries interrupt, and PFZ widen slightly. Tensile strength, elongation and EXCO rating of alloy are 758MPa, 8.4% and EA respectively.

Effect of Minor V Addition on Al88Y7Fe5 Amorphous Alloys

The effect of the addition of 0.2-0.65 at% of V on the glass forming ability and mechanical properties of Al88Y7Fe5 alloy were investigated. The addition of V in this range had little effect on the glass forming ability of the alloy, but lowered the tensile strength of the amorphous ribbon. The fracture surface of Al88Y7Fe5 amorphous ribbons was typical vein pattern for ductile metallic glasses, however, that of the alloy with 0.5% V addition changed to two different regions, i.e., vein pattern region and smooth region. At high magnification, the smooth region was composed of nanometer sized corrugations, which is typical for brittle metallic glasses.

Preparation of Micro-Hole with Large Aspect Ratio

It was difficult to prepare micro-hole with large aspect ratio by traditional processing technologies. In order to solve the problem, a preparation was proposed. It was carried out by casting method. Carbon fiber and metal wire coated graphite paint were used as hole core respectively. And morphology and geometrical characteristic of micro-hole were observed and analyzed by scanning electron microscope and laser scanning confocal microscope. The results showed that average diameter and aspect ratio of micro-hole obtained by the group of carbon fiber hole core were about 0.2 mm and above 1700, respectively. For the other group, about 0.5 mm and 700, respectively. The micro-hole obtained by the metal wire coated graphite paint hole core was more close to circle. Its shape factor was about 0.72. The roughness of micro-hole value obtained by carbon fiber hole core was close to 3.2 μm, smaller than that of the metal wire coated graphite paint.

Casting Process Design and Simulation for Shaft Locking Pin

Two kinds of methods of casting process for shaft locking pin were introduced. Simulated and analyzed the casting process by ANYCasting. Predicted the potential defects, resulted in a relatively optimized design. Replaced the traditional trial-and-error test with computer simulation, reduced design time and improved design efficiency.

Optimization Techniques in Numerical Simulation of Casting Process

This paper presents an overview and example using optimization techniques in casting numerical simulation. Most of the design work can fulfill with the software without human intervention. It really frees the engineer from the amount of trial-and-error that is necessary in traditional modeling.

A New Approach to Calculating Feeder Size and Location with Simulation Software

A new approach of feeder calculation was introduced in this paper. By using the simulation software, the feeder size and location can be calculated easily and test by run simulation, the results can be seen directly. Take the rocker arm as an example, the method was introduced by using SOLIDCast.

Effect of Charge Action on the Annular Molten Metal of Spray Forming

This paper described the effect of hollow jet atomization technology, under charge action, according to the spray forming process, to improve the quality of atomization. In order to deeply study the charge action on the annular molten metal of spray forming process, this paper analyzed theoretically quantity of electric charge of the annular molten metal and the surface tension of atomization droplets. The results show that the quantity of electric charge increases with the increasing of charging voltage. Under the same conditions, the hollow annular metal liquid charge is always greater than the solid cylindrical molten metal charge, but the surface tension is less than the solid molten metal. As the quantity of electric charge reduce the surface tension of the droplet, the power of atomization increases relatively. It means that the atomization quality of annular molten metal will be better than the solid cylindrical molten metal. By comparison, the structure under charge action is fine and homogeneous after experiment.

Study of Solid Solution Treatment on Spray Deposited 7A04 Alloy

The Al-Zn-Mg-Cu (7A04) alloys were prepared by using the method of spraying deposition and the hot extrusion. The effects of two-stage solid solution treatment and single solid solution treatment on the microstructure and mechanical properties of spray deposited 7A04 alloy were investigated. The microstructure and mechanical properties were observed and tested by optical microscopy, SEM, X-ray diffraction and other methods. It is indicated that the two-stage solid solution treatment is better than the single. After the two-stage solid solution, the sizes of recrystallization grains were small and a lot of precipitations were dissolved. And the microstructure was nice by ageing treatment. The tensile strength and elongation of the alloy can respectively reach 740MPa and 5.8 percent by the two-stage solid solution (at 450°C for 1 hour and 475°C for 2 hours) and the aging treatment.

A Study of Hollow Jet on Spray Forming

In order to improve the atomization quality of spray forming, the cylindrical hollow jet technology was applied in the atomization process of spray forming, and a numerical simulation for the structure of hollow flow field in front of jet outlet was carried out, the distribution of hollow jet flow field was simulated under different inlet velocities and outflow technologies, and then the experimental verification was performed. The simulation results of single-phase flow field show that with increasing the liquid inlet velocity, the back flow are a can get enlarged, and the lower negative pressure can be generated, which is beneficial for the out flow of liquid metal. The simulation results of two-phase flow field show that the hollow jet can be produced a hollow part. The conclusion basically accords with the experimental result of water flow.