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    • Rights: The University of Waikato
    Published 17 September 2009 Referencing Hub media
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    In this video, Stella Rayanova, a research assistant based in the Department of Engineering at the University of Waikato, explains how titanium-based alloy1 powders can be forged and extruded2 into different shapes.

    By carefully controlling the temperature3 and pressure4, it is possible to produce, from powder alloys, highly consolidated materials similar to those traditionally formed from molten alloys after casting.

    Transcript

    STELLA RAYNOVA
    Extrusion5 and forging they have different purposes. Forging is to make the final shape of the product and extrusion is just… it’s a semi-product to produce. You can press only rods with a cylindrical diameter or it can be rectangular, and after that, this semi-product can be used to produce something else.

    Traditionally, forging is used to make ingots from casting into the shapes. In powder metallurgy, we use forging in different terms because we are dealing with powders and we want to make our powders into a shape. It is basically, we are using a die, and the die has the shape that we really want to produce. We don't start directly from powders because powders are loose, and we need to heat6 the powders before we forge them.

    So what we do is we make a cold compact of the powders. Normally we used a cold pressed technique to make the powder into the cylindrical shape, and then we heat that green sample – we call it ‘green sample’ because it’s just a powder sample, it’s very weak – and then we heat it up to very high temperatures and then we put it into the forging die, and then we use a very high pressure to apply on the sample, and then the powder becomes the solid part.

    Extrusion is, again, it’s a metal7 to consolidate powders into the solid semi-products. Again, we have to make the cold compact, and then we have to heat it again, and then we put it into the extrusion die. And if the diameter of our cold compact is, for example, 20mm, after the extrusion, it may become 2mm. So normally we start with a cylindrical sample with a higher diameter and after extrusion we are producing a solid rod with a much smaller diameter. And it’s a great way for consolidation. If you imagine the density8 of the green sample, it’s around 65%, maximum 70%, and then after the extrusion, we have 100% density, and that’s the real product. After extrusion and forging, we are trying to achieve densities of 100%.

    Acknowledgement:
    Kerry Loewen

    1. alloy: A mixture of a metal with one or more other elements to modify its metallic properties, for example, brass is an alloy of copper and zinc.
    2. extrusion: A manufacturing process where material is forced through a shaped opening. The material is usually heat-softened to enable this.
    3. temperature: A measure of the degree of hotness or coldness of an object or substance. Temperature is measured with a thermometer calibrated in one or more temperature scales. Kelvin scale temperature is a measure of the average energy of the molecules of a body.
    4. pressure: The force per unit area that acts on the surface of an object.
    5. extrusion: A manufacturing process where material is forced through a shaped opening. The material is usually heat-softened to enable this.
    6. heat energy (heat): Heat energy: the transfer of energy in materials from the random movement of the particles in that material. The greater the random movement of particles the more heat energy the material has. Temperature is a measure of the heat energy of a material.
      Heat: the flow of energy from a warm object to a cooler object.
    7. metal: Any of a category of elements that usually have a shiny surface, are generally good conductors of heat and electricity and can be melted or fused, hammered into thin sheets or drawn into wires (for example, copper).
    8. density: How tightly a certain amount of matter (atoms or molecules) of a substance is compacted in a given volume. Density is commonly measured in grams per millilitre (g/ml) or cubic centimetre (g/cm3).
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      alloy

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      2. A mixture of a metal with one or more other elements to modify its metallic properties, for example, brass is an alloy of copper and zinc.

      pressure

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      3. The force per unit area that acts on the surface of an object.

      density

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      4. How tightly a certain amount of matter (atoms or molecules) of a substance is compacted in a given volume. Density is commonly measured in grams per millilitre (g/ml) or cubic centimetre (g/cm3).

      extrusion

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      5. A manufacturing process where material is forced through a shaped opening. The material is usually heat-softened to enable this.

      heat energy (heat)

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      6. Heat energy: the transfer of energy in materials from the random movement of the particles in that material. The greater the random movement of particles the more heat energy the material has. Temperature is a measure of the heat energy of a material.
      Heat: the flow of energy from a warm object to a cooler object.

      temperature

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      7. A measure of the degree of hotness or coldness of an object or substance. Temperature is measured with a thermometer calibrated in one or more temperature scales. Kelvin scale temperature is a measure of the average energy of the molecules of a body.

      metal

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      8. Any of a category of elements that usually have a shiny surface, are generally good conductors of heat and electricity and can be melted or fused, hammered into thin sheets or drawn into wires (for example, copper).

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