Anton Smolej

The influence of the thermomechanical processing and forming parameters on superplastic behaviour of the 7475 aluminium alloy

Abstract Aluminium AA7475 alloy (Al–Zn–Mg–Cu) was thermomechanically treated by four procedures which included various combinations of rolling, solution annealing, quenching and overageing. The influence of these treatment procedures on the size and the stability of crystal grains and on superplastic properties of the alloy, such as the highest elongation without localised neck, strain rate sensitivity values, and flow stresses were determined. The highest elongations were over 1000%. With simplified thermomechanical treatment without separate solution annealing and overageing, a sheet with elongations up to 590% was made in industrial conditions. Influences of the parameters of superplastic forming (working temperature, strain rate) on superplastic properties of the alloy were determined too.

Superplastic Behaviour of AA5083 Aluminium Alloy with Scandium and Zirconium

The aim of the present investigation was to determine and to compare the superplastic behaviour of the AA5083 (Al-Mg-Mn) alloy with Sc and Zr additions. The investigated alloys were processed to form sheets by conventional hot and cold rolling. The superplastic properties were determined with strain rates in the range of 1x10-4 to 5x10-2s-1 and forming temperatures of 350 to 550°C. The results showed that the alloy with about 0.4% Sc exhibited a high superplastic ductility across a wide temperature range and strain rates up to 1x10-2s-1. The highest elongations to failure of about 2000% were attained at 550°C and at an initial strain rate of 5x10-3s-1. However, the alloy with about 0.15% Zr exhibited elongations up to 600%. The FSP processed Al-4.5Mg alloy with combined addition of about 0.2% Sc and 0.15% Zr exhibited good superplastic properties at higher strain rates (> 1x10-2s-1) with elongations up to 1500%.

Strategy of Machinability of Aluminium Alloys for Free Cutting

Numerous aluminium alloys are suitable for cutting. The alloy of the type AIMgSiPbBi is used for free cutting. For free cutting, lead and bismuth are added to the alloy since they improve chip breaking and thus material machinability. Considering that the technology has to be adapted to the use of HSS tools, the research was focused in this direction. In addition to the basic machinability investigations, research was done also into the effects of deformation zone in cutting using Quick Stop Device (QSD). A relationship between the chip shrinkage ratio λ and shear angle φ was established. Both indicators are significant in assesing machinability af Al-alloys and can be included into the process technology database.

The superplasticity of friction stir processed Al-5Mg alloy with additions of scandium and zirconium

Abstract The paper describes the effect of minor additions of scandium and zirconium on the superplastic behaviour of friction stir processed Al-5Mg based alloy. The measurements included the flow curves and tensile elongations of (in wt.%) Al-5Mg-0.1Zr, Al-5Mg-0.2Sc, and Al-5Mg-0.2Sc-0.15Zr alloys at initial strain rates ranging from 1 × 10−3 to 1 × 10−1 s−1, and at forming temperatures from 350 to 500°C. The inclusion of friction stir processing at tool rotation rates of 95 and 475 rpm considerably enhanced the superplastic behaviour of the Al-5Mg-0.2Sc-0.15Zr alloy, which was reflected in elongations without failure of over 1900%. Other friction stir processed alloys, treated at lower tool rotation rates, did not achieve superplasticity due to abnormal grain growth. The results yielded by the friction stir processed alloys are compared with the superplastic behaviour of the same alloys produced conventionally by cold rolling.

Influence of heat treatment on the properties of the free-cutting AlMgSiPb alloy

Abstract The influence of the cooling rate after the homogenizing of free-cutting AlMgSiPb alloy on the stresses required for deformation after various times of heating onto the working temperature was determined. After the direct extrusion the alloy was treated by the extrusion-press quenching and by two stages of separate solution annealing in salt bath. Comparison of microstructural, mechanical and technological properties was made for the various heat-treatment processes applied.