Titanium Alloys - Characterstics of Alpha, Alpha Beta and Beta Titanium Alloys

Background

There are three structural types of titanium alloys:

        Alpha

        Alpha Beta

        Beta

The attributes of titanium alloys of prime importance to the design engineer are:

        Outstanding corrosion resistance

        Excellent erosion resistance

        High heat transfer capability

        Superior strength-to-weight ratios

Titanium alloys are also used because of their:

        Low thermal expansion co-efficient

        Non-magnetic character

        Fire resistance

        Short radioactive half life

Alpha Titanium Alloys

Commercially pure titanium and alpha alloys of titanium are non-heat treatable  and are genarally very weldable . They have:

        Low to medium strength

        Good notch toughness

        Reasonably good ductility

        Excellent mechanical properties at cryogenic temperatures

Pure titanium and alpha alloys possess the highest corrosion resistance.

More highly alloyed near-alpha alloys offer optimum high temperature creep strength and oxidation resistance.

Alpha Beta Titanium Alloys

Alpha Beta alloys are heat treatable and most are weldable. Typical properties include:

        Strength levels are medium to high

        High temperature creep strength is not as good as most alpha alloys

        Cold forming may be limited but hot forming qualities are normally good

        Many alloys can be superplastically formed

The most commonly used alpha beta alloy is Ti6Al4V, developed in many variations of the basic formulation for the widest possible choice of key properties  and for many widely differing applications.

Beta Titanium Alloys

Beta or near beta alloys are:

        Fully heat treatable

        Generally weldable

        Capable of high strengths

        Possess good creep resistance up to intermediate temperatures

        Excellent formability can be expected in the beta alloys in the solution treated condition

Beta-type alloys have good combinations of properties in sheet, as fasteners and are ideal for sporing applications. Some alloys offer uniform property levels through heavy sections.

The higher alloy content of beta alloys increases the density of beta alloys typically by 7-10% compared to Ti6Al4V.

Typical beta alloys include:

Ti3Al8V6Cr4Mo4Zr ASTM Grade 19

Ti10V2Fe3Al AMS 4983, 4984, 4987

Ti15Mo3Nb3Al2Si ASTM Grade 21

Ti15V3Cr3Sn3Al AMS 4914

Correctly, it is only the metastable beta alloys which are heat treatable by solution treatment and ageing. Fully stable beta alloys can only be annealed.

Source: Titanium Information Group.

For more information on this source please visit Titanium Information Group.

Comments

  1. David Smith David Smith United States says:

    I was hoping for information that would give me an indication as to a method for ductile formation of bata titanium without fracture. The reason for this inquire is that I have a bata Ti glasses frame that is old, 8 to 10 years, and I want to bend parts of them to better fit. I am concerned that they are near the point of fracture and thought a heat treatment might restore its ductility. How hot is a question since I don't want make them too soft? Does the heating need to be in an inert atmosphere to keep oxygen from combining with the Ti or is the temperature cool enough where that is not a problem? The alternative is to just bend them and if they fail, buy replacement parts, but I would like to avoid that and the article did not help me with this question.

  2. Patrick Thomas Patrick Thomas Ireland says:

    Which one of these types would be best suited for a pacemaker casing? Student doing a materials selection project btw :)

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoM.com.

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