Abstract
A method of mechanical alloying process is described. It was proved that the transformation efficiency of carbon to Al4C3 by heat treatment of aluminium with the porous furnace black and electrographite at temperatures 723 – 873 K and time periods 1 - 10 hours is higher than that of the hard cracked graphite. The size of Al4C3 dispersed phase was measured on thin foil and it was constant and as small as 30 nm. Subgrain size measured in the range of 100 grains in thin foils depended on the carbon type.. It ranged from 0.3 to 0.7 μm. Mechanical properties were analyzed in a microstructural matrix (after extrusion) as well as in nano-matrix The temperature dependence of ductility, and reduction of area in the temperature range of 623 – 723 K and strain rate of 10-1 s-1, indicated a considerable increase of properties. In a case when the volume fraction of Al4C3 changes from lower to higher, the grain rotation mechanism dominates instead of the grain boundary sliding. Creep parameters for Al-Al4C3 systems and commercial IN9021 and IN9052 systems were compared. The dependence of the minimum deflection rate on the applied force as well as the dependence of the time to fracture on the applied force for two temperature levels (623 and 723 K) by small punch testing is depicted. The anisotropy of the creep properties and fracture using small punch tests for the Al-Al4C3 system produced by ECAP were analyzed.
Highlights
Since strengthening of aluminium alloys by Al4C3 particles can be expected to have great potentiality for increasing their high temperature mechanical properties, creep and creep fracture in such alloys have been investigated extensively [1, 2]
Because these effects are similar to other ones, obtained by nonequilibrium techniques, such as rapid melt solidification, the system is characterized by increased mechanical properties
The aim of this paper is to study the influence of the various graphite types and heat treatment procedure on the microstructure, mechanical properties and fracture of dispersion strengthened aluminium alloys in the Al4C3 system with micro and nanostructures
Summary
Since strengthening of aluminium alloys by (noncoherent) Al4C3 particles can be expected to have great potentiality for increasing their high temperature mechanical properties, creep and creep fracture in such alloys have been investigated extensively [1, 2]. Aluminium alloys strengthened by Al4C3 particles are produced by mechanical alloying and/or reaction milling. The process is implemented in laboratories in attritors, on the industrial scale in high energy ball mills It is based on deformation, repeated disintegration and welding of power particles during intensive dry milling [4, 5]. It is remarkable that the crystalline phases are usually of the nanometric size Because these effects are similar to other ones, obtained by nonequilibrium techniques, such as rapid melt solidification, the system is characterized by increased mechanical properties. The aim of this paper is to study the influence of the various graphite types (when mixed with Al powder) and heat treatment procedure on the microstructure, mechanical properties and fracture of dispersion strengthened aluminium alloys in the Al4C3 system with micro and nanostructures
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