Variation of high pressure torsion processing modes for fabrication of the Al-Nb hybrid system

A hybrid composite material fabricated from the Al – Nb system using severe plastic deformation by high-pressure torsion (HPT) up to 30 turns has been studied in the present work. To fabricate the composite, deformation of a three-layer Al – Nb – Al package was carried out at room temperature on Bridgman anvils with grooves under a pressure of 5 GPa at N = 10, 25 and 30 revolutions, at a strain rate of ω = 1 and 2 rpm. Initial disc diameters from pure metals and HPT conditions were experimentally optimized to obtain monolithic and defect-free composite samples. The most intensive fragmentation and stirring of niobium in the aluminium matrix was observed if diameter of aluminium discs was 10 mm and deformation conditions N = 25 and 30 revolutions and ω = 2 rpm were applied. Three microstructural zones were observed after HPT under optimal conditions: the central zone with wide curved layers of niobium in aluminium, the mid-radius zone with finely dispersed layered structure, and periphery with a uniform distribution of niobium in the aluminium matrix. It was shown that HPT led to formation of the intermetallic Al3Nb phase. The microhardness measured along the diameter of the obtained composite materials changed nonmonotonically depending on the produced structure (microstructural zone).

Study on Compression-Torsion Deformation Behavior and Recrystallization Grain Size of Mg13Gd4Y2Zn0.5Zr Alloy

In this paper, the compression-torsion composite deformation of homogenized Mg-13Gd-4Y-2Zn-0.5Zr alloy with strain rate of 0.001 s-1-0.5 s-1 during the temperature interval of 350 °C-480 °C was studied by the torsional test using the equipment of Gleeble3500 unique to North University of Chain. The effects of temperature and strain rate on the flow behavior of the alloy during compression-torsion deformation were investigated. And the compression-torsion constitutive equation of the high temperature flow stress of the alloy was constructed by introducing the temperature compensation factor Z, providing a theoretical basis for subsequent finite element analysis. The results showed that the flow stress increased with the increase of strain when the flow curves of the alloy were 350 °C and 400 °C. When the deformation temperatures were 450 °C and 480 °C, the flow stress was a typical recrystallization type. The influence of temperature and strain rate on dynamic recrystallization behavior was investigated by OM observation. The results showed that the number and size of recrystallized grains increased with the increase of temperature at the same strain rate, and the number and size of recrystallized grains increased with the decrease of strain rate at the same temperature.

Calculated model of sleeve bearing lubricated with melt in turbulent conditions of friction

The paper reports the description of cutting problems connected with surface quality at chip formation. There is developed a bench for computer diagnostics of a cutting process at composite planning. In the course of investigations there was adduced a hypothesis of elastic deformation at composite cutting. A procedure is presented on the basis of a diagnostic center use. The results of the experimental investigations of chip formation dynamics and machining quality are obtained. The experimental investigations in the SAE program on composite deformation during chip formation at jointing are carried out. The diagrams of dependences and descriptions of conclusions, recommendations and conclusions on the use of SAE programs and a computer diagnostic center are obtained.

Peculiarities of deformation phenomena during chip formation at composite orthogonal cutting

The paper reports the description of cutting problems connected with surface quality at chip formation. There is developed a bench for computer diagnostics of a cutting process at composite planning. In the course of investigations there was adduced a hypothesis of elastic deformation at composite cutting. A procedure is presented on the basis of a diagnostic center use. The results of the experimental investigations of chip formation dynamics and machining quality are obtained. The experimental investigations in the SAE program on composite deformation during chip formation at jointing are carried out. The diagrams of dependences and descriptions of conclusions, recommendations and conclusions on the use of SAE programs and a computer diagnostic center are obtained.

Tool-part interaction in composites microwave curing: Experimental investigation and analysis

The tool-part interaction of composite materials during microwave curing is different from conventional thermal heating, mainly because of the rapid and selective heating mechanism of microwave. Novel measurement and analysis approaches of microwave curing induced tool-part shear stresses were established and verified in this article. The optical fiber sensors were placed in the groove of tool surface to measure the strain values, which were converted to the tool-part shear stresses. A comprehensive friction coefficient was calculated by the shear stresses, and it was presented by considering the thermal expansion mismatch of composite/tool and the chemical shrinkage of resin. In order to validate the accuracy of model, the shape dimension of microwave cured scaling down leading edge of the composite part was measured to compare with simulation model. The results exhibited that the presented model can significantly decrease the prediction error of composite deformation compared with other methods during microwave curing.