Effect of Precipitation Hardening on Elastic Modulus

In summary, the conversation discusses the use of spring rings made from Inconel 718 that were ordered in an annealed, "dead-soft" condition. The speaker, who is not a materials expert, is trying to determine if the rings are still usable in this state and if the elastic modulus can be deduced from the hardness. The conversation concludes with the understanding that the hardening process mainly increases hardness and strength, and the main concern is whether or not the rings will fail in use.
  • #1
minger
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Hey guys, we have ordered some spring rings made out of Inconel 718. For some reason the company didn't finish the heat treat and the parts are just annealed, in the "dead-soft" condition.

I need to evaluate if these things are usable (they are actually supposed to be soft and were designed to be as soft as possible). Unfortunately I'm not a materials guy and cannot find any info on an "as-annealed" state of this stuff. Given a properly heat-treated piece, is there anything I can deduce about the elastic modulus from simply the hardess, or at least make a guess?

FYI, The spec calls for >36.0 HRC, and we have HRB 92, which ~14 HRC

Any help? Thanks,
 
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  • #2
Forgive me if this comment is too basic, but elastic modulus is relatively insensitive to changes in microstructure such as precipitate size or density. (Hardness is a measure of resistance to permanent deformation, while elastic modulus is a measure of resistance to elastic deformation.) For example, steels are generally far harder than iron, their main constituent, but have approximately equal stiffness. Is there a reason you think that your specific samples would vary far from the general Inconel elastic modulus of ~200 GPa?
 
  • #3
Hi minger. I agree with Mapes. I've seen a lot of data and never seen anything that indicates a change in modulus due to change in hardness.

If the springs are annealed, I'd be much more concerned with the material yielding when put into use.
 
  • #4
OK, so the hardening pretty much only increases hardness and strength? Then, I only need to analyze whether or not these things will fail?

gotcha, thanks a bunch.
 

What is precipitation hardening and how does it affect the elastic modulus?

Precipitation hardening is a heat treatment process used to increase the strength and hardness of certain alloys. When certain elements are added to a metal alloy, they form small particles called precipitates. These precipitates act as obstacles to dislocation movement, making the alloy stronger and harder. This increase in strength also leads to an increase in the elastic modulus, which is a measure of a material's stiffness.

What are the factors that influence the effect of precipitation hardening on elastic modulus?

There are several factors that can influence the effect of precipitation hardening on elastic modulus. These include the type and concentration of alloying elements, the heat treatment process used, the aging temperature and time, and the cooling rate after aging. The composition and microstructure of the alloy also play a significant role in determining the final elastic modulus.

How does the aging process affect the elastic modulus in precipitation hardened alloys?

The aging process is a crucial step in precipitation hardening and can significantly affect the elastic modulus of the alloy. During aging, the precipitates in the alloy undergo changes in size, shape, and distribution, which can lead to changes in the elastic modulus. The aging temperature and time must be carefully controlled to achieve the desired elastic modulus in the final product.

What are some common applications of precipitation hardened alloys with high elastic modulus?

Precipitation hardened alloys with high elastic modulus are often used in applications where strength, stiffness, and corrosion resistance are essential. Some common applications include aerospace components, medical implants, high-performance sports equipment, and structural components in buildings and bridges. These alloys are also used in high-temperature applications, such as gas turbines, due to their excellent mechanical properties at elevated temperatures.

Can the elastic modulus of a precipitation hardened alloy be adjusted after the aging process?

Yes, the elastic modulus of a precipitation hardened alloy can be adjusted after the aging process through a process called overaging. Overaging involves heating the alloy at a slightly higher temperature for a longer time, which leads to a decrease in the strength and hardness of the alloy. This decrease in strength also results in a decrease in the elastic modulus. Overaging is commonly used to achieve a specific elastic modulus for a particular application.

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