The effect of alloying elements on material properties


This article is all about alloying element's effect on a particular mechanical property. These main alloying elements are Aluminium, Cobalt, Copper, Chromium, Lead, Manganese, Molybdenum, Nickel, Silicon, Sulphur, Titatium, Tungsten and Vanadium.

What is an Alloy?


An alloy is a combination of more than two metals mixed or added together in order to obtain desirable material properties which may be physical or mechanical. Normal metal does not contain all the required material properties that one need but by adding various metals with corresponding metals, one can obtain desirable and enhanced material properties.

Examples of alloys


  • Copper and Copper alloys: Copper is available 99.95 % pure if it is totally electrolytically refined. Copper has two major alloys (a) Brass=Copper+Zinc (b)Bronze=Copper+Tin. Less pure copper is used for chemical plant and plumbing works for domestic applications. Copper is available in the form of sheet, wire, strip, round bar as well as in plate and tube.

  • Aluminium and Aluminium alloys: Pure Aluminium is available in 99 % to 99.99 % purity level and it is soft as well as ductile but having low hardness. It is practically more difficult to cast Aluminium which is available in pure form, so alloying elements are needed to cast it properly. Alluminium alloys are maily classified in (a) Wroght alloys and (b) Casting alloys. Due to light weight of Aluminium as well due to cost effectiveness, it is widely used in many applications


  • Effect of Alloying elements on material properities


    Here are list of most widely used alloying elements in alloy steels to enhance desired material properties.

    Aluminium


    Aluminium acts a oxidizer to increase the resistance to oxidation and scaling formation. It helps to increase nitriding, restricts grain growth and also reduces the strength upto 0-2% range.

    Chromium


    As alloying element, Chromium improves wear resistance for rubbing applications, also increase resistance against oxidation and scaling. It also increases high temperature strength.

    Cobalt


    Cobalt as alloying element provides air hardening and resistance to scaling formation. Also it improves the properties for cutting operation by tool steel with 8-10%. Along with Chromium, Cobalt gives certain high alloy steels having high temperature scaling resistance.

    Copper


    Copper added with 0.2-0.5 % composition in pure metal, improves the corrosion resistance and also yield strength for low alloy steels.

    Lead


    With lead, pure metal obtains increased machinability properties in plain carbon steels

    Manganese


    Manganese drops sulphur brittleness and acts as hardening agent (increases hardness) upto 1% and also it improves strength and toughness.

    Molybdenum


    As alloying element Molybdenum is a carbide forming element which promotes grain refinement to increase hardness and high temperature strength, creep resistance. It also reduces the temper brittleness in Nickel-Chromium steels.

    Nickel


    The alloying rangeis 0.3-5% and it improves strenght, toughness and hardenability without affecting ductility. Also corrosion resistance increases due to addition of Nickel in pure metal. Nickel promotes an austenitic structure.

    Silicon


    The maximum addition range is 0.2-3% and it improves hardenability and strength but reduces ductility. Silicon is also known for its deoxidizer ability.

    Sulphur


    Suphur forms sulphides which improves machinability but at the same time reduces ductility and weldability.

    Titanium


    Titanium as alloying element improves strength. It acts as carbide forming agent. It stabilizes austenitic stainless steel.

    Tungsten


    It forms hard stable carbides and promotes grain refining with increase in hardenss as well as toughness at high temperature. It is used as main alloying element to make high speed tool steel. It is also used for permanent magnet steels.

    Vanadium


    Vanadium is carbide forming element and deoxidizer used with Nickel and/or Chromium to increase the strength. It improves the hardenability and does grain refinement. As a deoxidizer it is useful for casting steels, high speed and pearlitic Chromium steels.

    Conclusion


    Thus by reviewing the above alloying element properties, one can choose the alloying element and get desired material properties for required applications. Thus alloying elements are used in base metal or pure metal to refine and improve the existing material properties.


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