MSE307

MSE307 Engineering Alloys

In third year, I teach 1/3 of a course on alloys. This is quite different to my other courses in that it is all about the skill of synthesis; taking all of the ideas and concepts and phenomena encountered so far in the degree and applying them to understand the domain of alloys. That is; how alloys are designed, how they are manufactured, and how they are used, and how all of these inter-relate.

It could be a course of unrelated facts! But the 1st and 2nd year material actually gives you a framework to put them together into a whole – to turn the trees into a forest, the threads into a tapestry – which is that skill of synthesis.

My intent is to add videos here and then to discuss in the class sessions for lectures 2-8 using learning catalytics, but the first lecture will be by classical exposition, at least for 2015. I will add the notes and videos to this page as I make them.

And so in the first lecture I first introduce the course, then we discuss materials selection, then jet engines to get into an application context, then lifing to think about the topic of failure.  Notes for lecture 1. Video 1.1.  Video 1.2.

The second session is about the melting and forging or speciality aerospace alloys (mostly Ni, Ti, Zr and some steels).  Lecture 2 NotesVideo 2.

The third session is about the Sioux City air accident, examining the fault sequence, the causes of the failure and the underlying metallurgy. Lecture 3 NotesVideo 3. The air accident report is here.

In the fourth lecture we discuss some theoretical concepts in alloying. Lecture 4 notes. Video 4.  A good paper on Blackman diagrams is here.

In the fifth lecture we turn to titanium alloys. The first lecture of the set of four is on the phase metallurgy. Video 5. Lecture 5 Notes.

The sixth lecture is about the formation of microstructure in titanium alloys. Video 6. Lecture 6 Notes.

Then, in lecture 7 we discuss mechanical properties, and begin a discussion on fatigue behaviour. Video 7. Lecture 7 Notes.

And finally in lecture 8 we wrap up the discussion of fatigue by discussing dwell fatigue, after which we review the non-mainstream Ti alloys. Video 8. Lecture 8 Notes.

Other links

Rolls-Royce – jet engine fly-through, assembly etc are here.

Animation from ORNL of Ti processing from Kroll to cold rolled sheet: here.

14 Responses to MSE307

  1. john says:

    Looking forward to second video.

    Great lecture, thank you for sharing!

  2. Safouane says:

    Looking forward to seeing this course. Thank you for the huge effort you put into your courses!

  3. Neil Samsoon says:

    I love you David Dye!

  4. yan says:

    Hello prof Dye,

    I’d like to ask a question. For the lecture 5, in the phase diagram of Al Ti, if Al is less than 6 wt% and we cool down Ti to room temperature, how can we form a+b phase field which is desirable for forging? Thanks

    • dyedavid says:

      Forging is, by definition, a hot deformation process. So by adding (any element) to pure X in a binary phase diagram, you create a two phase region (Gibbs phase rule, ref MSE104 and MSE204). So, in a Ti-Al alloy, there will necessarily be a 2-phase region to forge in. This is widely used for alloys with an allotropic transformation – the same is true for dual phase rolling in steels, for example.

  5. yan says:

    Dear prof Dye,

    I don’t understand the link between b stabilizer which can reduce the solvus temperature at above 600 C and the stabilisation of b phase at room temperature. Why b stabiliser which reduces the solvus temperature at high temperature can help to form b phase at room temperature? Many thanks.

    • dyedavid says:

      A beta stabiliser is defined as an element that reduces the beta-> alpha+beta transformation (solvus) temperature. If you add enough beta stabiliser, then assuming that there are no eutectoids, it must be possible to stabilise beta all the way to room temperature – and in most Ti binaries, at least optically, this is so for quenching – although the beta might be metastable.

      • yan says:

        Thank you for your reply. But among the 4 phase diagrams showed in lecture 5, there is not one who has the beta-> alpha+beta transformation solvus line down to the room temperature. So only by quenching, it is possible to obtain beta, otherwise if we cool down slowly we can only obtain alpha. Is that right? Many thanks.

      • dyedavid says:

        Below about 500C, we don’t know what happens to the true equilibrium phase diagram for most of these systems – because diffusion is too slow to reach equilibrium. So we are necessarily in a metastable state if we cool a beta alloy from, say, 700 or 800C. What happens then we find out by experimentation. Often if we take a heavily beta stabilised alloy and cool from a forging temperature, we form omega on low temperature (300C) ageing, which we may then be able to use to nucleate alpha at 400C. This is an active area of research.

  6. Monica says:

    Hello Prof. Dye,

    The link to the paper on Blackman diagrams is broken. Could you find another paper to reference? Would be greatly appreciated!

    Thanks!

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