Compact Extrusion Research Articles

Effect of Powder Compact Holding Time on the Microstructure and Properties of Ti-6Al-4V Alloy Produced by Powder Compact Extrusion of a Powder Mixture of HDH Titanium and Al-V Master Alloy

Ti-6Al-4V (wt%) alloy rods were prepared successfully using a low-cost method that combines mixing HDH titanium, elemental aluminum and Al-V master alloy powders and powder compact extrusion. The microstructure and mechanical properties of Ti-6Al-4V alloy and the effects of powder compact holding time on them were investigated. The results showed that powder compact holding time had a significant effect on the microstructure and mechanical properties of the extruded Ti-6Al-4V alloy rods. With increasing powder compact holding time from 2 to 10 min., the microstructure of the extruded rods became more homogeneous, and their UTS decreased from 1300 to 1215MPa and the elongation to fracture increased from 7.1 to 10.2%. The tensile properties of the Ti-6Al-4V alloy rods produced by powder compact extrusion of the powder mixture are comparable to those of Ti-6Al-4V alloy produced by ingot metallurgy and thermomechanical processing.

Preparation, Microstructure and Properties of Ti-6Al-4V Rods by Powder Compact Extrusion of Powder Mixture

Ti-6Al-4V (wt%) alloy rods were prepared successfully using a low-cost method that combines mixing elemental and master alloy powders and powder compact extrusion. The microstructure and mechanical properties of the rods and the effects of extrusion temperature on them were investigated. The results showed that the microstructure and mechanical properties of the extruded rods were strongly affected by the extrusion temperature. With increasing extrusion temperature from 1200°C to 1300°C and keeping the powder compact holding time unchanged at 2 minutes, the fraction of undissolved V rich particles in the microstructure of the extruded rod decreased substantially to zero, the level of composition homogenization increased dramatically to the highest level, and the UTS and elongation of the extruded rods increased significantly from 886MPa and 1.2% to 1300MPa and 7.1%, respectively. The tensile properties of the Ti-6Al-4V alloy rods produced by powder compact extrusion of the powder mixture are comparable to those of Ti-6Al-4V alloy produced by ingot metallurgy and thermomechanical processing.

Experimental and Numerical Investigations on Metal Flow during Direct Extrusion of EN AW-6082

In extrusion processes metal flow has an important influence on the microstructure and the mechanical properties of the extrudates. Thus, a deep knowledge about the metal flow during the forming process is required as basis for further computations of the microstructure evolution. In this study experimental and numerical investigations on the influence of friction on the metal flow in extrusion processes were carried out using visioplastic methods and finite element method (FEA). The objective was to determine the influence of ram speed, ram displacement and billet temperature on the material flow during extrusion of the aluminum alloy AlMgSi1 (EN AW-6082). For this purpose the forming stroke was varied at constant temperature so that a butt length of 100 mm and 150 mm could be produced. Further the influence of different ram speeds at 4.22 mm/s, 6.33 mm/s and 8.44 mm/s was investigated. In order to identify the metal flow and in special the shear zone as well as the dead metal zone, the billets of 250 mm length and a diameter of 140 mm were prepared with round aluminum indicator pins with a diameter of 4 mm which were placed in the plane of symmetry of the billet. For the experimental investigations a compact direct extrusion press with a nominal force of 10 MN (SMS Eumuco) was used. The numerical simulations were carried out using the commercial FEA system simufact.forming 8.1. After extrusion the billets were cut in the plane containing the indicator pins and the surface was polished and etched. The visioplastically determined flow lines and calculated strains were compared with computed flow lines in order to verify the results and to parameterize the simulation. Tresca’s friction model was used in the simulations to describe the frictional conditions between the billet and the tool components. The results of the experimentally and numerically determined strains of the billet at the container wall show a good similarity. With respect to the rigid modeling of the tool components and the fact that Tresca’s friction model considers relative speeds only indirectly the computed ram force curves show also quite good agreement with measured curves. However, the simulation results demonstrates that in further numerical studies advanced plastic flow criteria and flow rules should be used that take into account the anisotropy and inhomogeneity due to the changing grain size and microstructure of the workpiece material.

Consolidation of Titanium, and Ti-6Al-4V Alloy Powders by Powder Compact Forging

Consolidation of titanium and titanium alloy powders using thermomechanical powder metallurgy (TPM) processes (powder compact forging, extrusion and rolling) is one way that can lead to cost-effective production of high value-added consolidated titanium and titanium alloy products such as near-net shaped components, tubes and plates. This paper provides an overview of the quality, microstructure (to limited depth), porosity level and mechanical properties of disks produced using open die forging of powder compacts of CP titanium and Ti-6Al-4V alloy powders. The general materials science principles underlying the relationships between processing conditions, microstructure and the mechanical properties of the disks made by using the powder compact forging are discussed.

Features of the development of extrusion granulation of biofuel based on wood and plant waste products

The problem is considered of using granulated fuel from sawdust as a replacement for traditional energy sources, and the advantages of wood granules over other types of fuel are demonstrated. Results are provided for a study of the behavior of sawdust in a channel during continuous compaction. Results are given for a study of the effect of temperature on the change in plastic strength of the original raw material. It is shown that use of heating leads to a reduction in the specific compaction pressure, and this makes it possible to reduce energy expenditure and to increase the efficiency of preparing the final product. Operating principles are considered for rotary presses and also forces that operate on the compacted mass at a deformation site. A series of equations is provided describing material behavior in an extrusion compaction channel, and also the connection of channel geometric parameters and reprocessed material properties.

Compaction of ultra-fine Al powders

The possibility of preparing bulk sub-micron grained profiles with superior mechanical properties was investigated. A bottom-up route was used, wherein commercial ultra-fine powders were consolidated with the aim of preserving the initial fine-grained structure and thus obtain unique mechanical properties. A relatively simple and cheap technique for preparation of Al bulk profiles through conventional direct extrusion compaction was established. During extrusion initial powder particles were deformed and fragmentised into ultra-fine elongated grains mostly aligned along the extrusion direction. Moreover, extensive energy induced into the input powder during compaction yielded fine distorted oxide dispersoids homogenously distributed within the final compacts. These do in fact represent MMC where Al matrix is reinforced with nanoscale alumina particles. The influence of powder size and other processing parameters on consolidation behaviour and mechanical properties of compacted profiles, their structure and thermal stability are reported and discussed. Overall comparison with conventionally prepared SAP materials is made.

Compaction of amorphous aluminum alloy powder by direct extrusion and equal channel angular extrusion

Al 89Gd 7Ni 3Fe 1 alloy powder produced by gas atomization was consolidated using equal channel angular extrusion (ECAE) and direct extrusion. The powder particle size was below 30 μm and the as-received powder was ∼70–80% amorphous. ECAE compaction of loose powder was conducted at 200 °C. The microstructure of the compacted material was studied after different levels of ECAE deformation, which allowed analysis of the mechanism of particle interactions, deformation and bonding during different stages of consolidation. Direct extrusion compaction was conducted at 210, 250, 400, and 450 °C. After compaction at 210 °C, the material was about 70% amorphous and it had 98–99% of the theoretical density. A fully dense alloy with a nanocrystalline structure (grain size ∼700 nm) was produced after extrusion at 450 °C. Extrusion at 250 and 400 °C led to poor consolidation of the powder due to formation of brittle intermetallic phases with volume fraction of about 40%.

Compactability of Stabilized Zirconium Dioxide Powder

Features of compacting articles from stabilized zirconium dioxide powder synthesized by the sol-gel method, and also their structure and properties are studied. Compaction parameters are determined. It is shown that the relationship between compact density and extrusion pressure may be described by the Bal'shin equation. It is established that parameters of this equation depend linearly on the duration of zirconium dioxide synthesis.

Analysis of extrusion compaction of fibrous agricultural residues for fuel applications

The consolidation stage in the compaction of fibrous agricultural materials in an extrusion press has been analysed in order to provide design equations for the optimal choice of die length and estimation of the pulsation domain (region of the die where the material expands and is recompacted repeatedly), for minimisation of die wear. An analysis of the heat flow and transfer processes in the die and the material is also provided. Application of the analyses to the development of a non-frictionally heated biaxial press is discussed. The heated press is designed to be a compromise between conventional extrusion and piston presses, to optimise the qualities of briquettes with power input into material compaction.

A rheological model for the compaction of fibrous agricultural materials

A five element non-linear rheological model was developed for analysing the compression and relaxation behaviour of fibrous agricultural materials. The model's mechanical elements have non-linear characteristics (unlike existing models), and feature a creep curve that approximates more closely to the real behaviour of fibrous materials. The model's response to an applied compressive load has three stages, namely, inertial up to the initial density, elastic up to the elastoplastic point, and thereafter elastoplastic. Mathematical analysis of the model involves non-linear differential equations developed from the compression and creep response of the material, thus making the model parameters more closely related to the physico-mechanical properties of the compacted material. Such properties, found to be dominant in the post-compression recovery and permanent deformation phases of the material, include the elastic resistance, the plastic modulus and the internal friction of the wafer formed. Application of the model to extrusion compaction indicates the significant effect which thermoplastic strains have on the creep response of a fibrous material. Analysis of experimental results with the model indicate an optimum hold time of 2·5 and 5s for ground and unchopped barley straw samples, respectively, and higher values of residual elastoplastic resistance for the unchopped samples; residual permanent deformation was estimated to constitute 54–77% of total material deformation.

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

AbstractThis 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

アルミニウムおよび銅粉末圧密体の熱間押出しにおける加工力と変形

アルミニウムおよび銅粉末圧密体の熱間押出しにおける加工力と変形

Manufacture of nickel base composite materials with dispersed glass particles by the powder metallurgy method. Part I

1. A technique has been developed for the manufacture of rods of nickel base composite materials containing crystallizing glass particles. Such rods are characterized by a uniform distribution of dispersed phase particles throughout the metal and have densities close to theoretical. 2. A study was made of the specific load in the extrustion of sintered compacts as a function of the amount and nature of the dispersed phase in nickel. The use of silicate materials which react chemically with nickel substantially increases the specific load. 3. The use of glass rather than graphite lubrication appreciably decreases the specific load in the extrusion of compacts.