Full Transcript:

What’s up guys? This is Michael with Michael Talks Metal back for another talk on low expansion alloys. Today is Alloy 42, 45 and 49 so we’re going to EXPAND A LITTLE (I’ll be here all week) on our last video about  the Iron-Nickel alloys that exhibit  low thermal expansion characteristics. We discussed expansion and CTE n some detail in the previous video.  Click here if you have not seen that video on Invar 36.

Low expansion alloys are used in applications to either:

minimize changes in dimension with change in temperature


expand at a similar rate to another material over a range of temperature


create motion when coupled with higher expansion materials over a range of temperature

Examples of applications include thermostats, stable structures for lasers and other sensitive equipment, and seals to glasses and ceramic materials.

Invar 36 has a nominal  Nickel content of  36 % and  the Low Expansion 42, 45, and 49 alloys have a nominal Nickel content of 42 %, 45 % , and 47.5 % respectively .   I know, you guessed that last one would be 49.  Me too.

Last week we saw that Invar 36 had a very low rate of expansion, so why are there other low expansion Iron – Nickel alloys?

While still low compared to most metals, the expansion rate of these alloys increases with  increasing Nickel content…but the Curie temperature also increases making them useful at increasing temperatures.

At the Curie Temperature, the change in magnetic structure also results in an abrupt undesirable increase in thermal expansion characteristics.

Lets look at how the Curie temperature and expansion rate compare:

Low Exapansion Alloys - Expansions

  Nominal Chemical Composition

Low Expansion Alloys - Chemistry

Are these alloys – Alloy 42, Alloy 45, and Alloy 49 Magnetic: Yes, Alloy 42, Alloy 45 and Alloy 49 are magnetic up to Curie Temperature


Low Expansion 42        .294 lbs per cubic inch

Low Expansion 45        .296 lbs per cubic inch

Low Expansion 49        .298 lbs per cubic inch

Typical Mechanical Properties in the annealed condition:

Tensile Strength:     75,000 psi

Yield Strength:        40 ,000 psi

Elongation:                30 %

Hardness:    80   Rockwell B


ASTM B 753

As we have told our viewers many times before, specifications, prints,  and part requirements  can add to or alter the information we have presented to you today….So  CHECK THE SPECS – 64th time. Twice. So this is Michael with Michael Talks Metal, Michlin Metals is a distributor and supplier of low expansion alloys, check out website www.michlinmetals.com for more info. If you missed our previous video on Invar 36, click here. If you made it this far and haven’t subscribed, click here! Thanks for watching, this is Michael with Michael Talks Metal, see you next Thursday 10am, I’m out!