A study on powder extrusion is attempted to extend the understanding of the extrusion process and the interrelationship between process variables and forces involved. The extrusion characteristics of a promising Al-Si alloy produced from rapidly solidified powder, and the effects of such variables as temperature, reduction ratio, and die geometry on extrusion pressure and friction force have been investigated. Results show that extrusion starts prior to the attainment of a peak pressure. The friction force between the billet and lubricated container occupies only about 4.5% of the peak pressure. This friction is therefore not principally responsible for the pressure drop of about 50% from a peak value to a steady state occurring during extrusion—a finding which is in conflict with the traditional understanding of extrusion. It is also found that temperature-compensated strain rate Z can satisfactorily reflect the combined effects of the process variables on the pressure requirement. The relationship between the Z parameter and the pressure required for the extrusion of the powdered metal (PM) alloy has been formulated, and thus together with the consideration of press capacity and product quality, the extrusion process can be well controlled.

Extrusion of an aluminum alloy prepared from rapidly solidified powder

A study on the optimization of extrusion conditions for a prospective Al-20Si-3Cu-1 Mg alloy prepared from rapidly solidified powder was carried out by evaluating tensile properties at room and elevated temperatures. It was found that extrusion conditions influence the asextruded microstructure and mechanical properties of the alloy to a certain extent. The relationship between the as-extruded mechanical properties and such extrusion variables as temperature, reduction ratio and die shape, can be described by using temperature-compensated strain rate, so that the as-extruded properties can be tailored in a certain range by adjusting this process parameter. In addition, the comparison between the as-extruded and as-T6 tempered tensile properties at elevated temperatures has opened the question as to the necessity of applying the heat treatment to the alloy — a normal practice subsequent to the extrusion. The experimental results suggest that for the material used at temperatures at and above 200 °C, the T6 temper treatment can be eliminated.

https://link.springer.com/content/pdf/10.1007/BF01184964.pdf

Effect of extrusion conditions on mechanical properties of Al-20Si-3Cu-1 Mg alloy prepared from rapidly solidified powder

The effect of long-time homogenization and aging on the formation of disperse β′ phase particles and β phase particles has been analyzed. Alloys solidified with the cooling rate of ∼10− 1 °C/s (Al–10%Mg and Al–10%Mg–0.1%Sc) and alloys melted by centrifugal casting with the cooling rate of ∼ 103 °C/s (Al–10%Mg) were chosen for comparative analysis. А significant heterogeneity of the distribution of the strengthening β′-phase after aging is observed in Al–10%Mg alloys obtained by the ingot technology. The greatest hardening up to 100% is achieved after using the centrifugal casting due to the formation of the β′-phase during aging.

Peculiarities of nanostructured state formation in heat-treatable Al–Mg alloys

This communication reports work completed on the extrusion of powder compacts prepared from rapidly solidified Al–10 Mg powder. It is shown that mechanical properties of the extrudate are related to the temperature compensated strain rate obtaining during the extrusion process. Pressure requirements are much lower than are necessary for the extrusion of cast products of Al–7Mg and Al–5Mg and the corresponding increase in heat generation considerably widens the extrusion limits. In the as-extruded condition, the properties are comparable with a peak aged conventional 7050 alloy but the Al–10Mg is extremely unstable and requires an aging treatment to correct this instability. It is concluded that improvement in this alloy system would be obtained either by decreasing the Mg content or by developing a lower %Mg ternary alloy. PM/0280

T. Sheppard

Papers

Extrusion and Properties of an Al–10Mg Alloy Prepared from Rapidly Solidified Powder