SAE Update - January 2022 - 19

Holistic materials selection
TECH FOCUS:
MATERIALS
created through non-SAE standards bodies
may have multiple compositions within one
document, so care must be taken to procure
the specific material requested.
Often, the understanding of material
procurement requires traversing a network
of material, process, heat treatment, and
surface condition specifications. The
specifications contain cross-references to
locate information about the specific process
path. The processes in-place for material
procurement have large effect on the
microstructure and properties of a material
and final part. The SAE Mobilus platform is a
centralized location to obtain digital
standards for materials and processes from
AMS, and additionally allows browsing of
prior specification revisions to understand
how the documents have changed and
evolved over time. Some standard
specifications require specific surface
treatment, like a molybdenum-disulfide
coating on a fastener. These processing
steps are clearly defined as necessary before
the material is placed into end-use.
Familiarity with these documents provides
an understanding of the common features of
materials in the industry, and any
customization of the standard processes
invites schedule delays and cost increases. In
describing availability, the concept of a
warehouse, grocery store, or distribution
center is useful to convey. " Off-the-shelf "
product is anything that can be readily
purchased in the final condition, at rapid
speed. Things like processed loaves of bread
UPDATE
from a grocery store can be purchased every
day reliably, whereas a customized cake
must be ordered from the bakery ahead of
time, with increased cost and delay until the
product can be eaten. Similarly, custom heat
treatment or chemical composition requires
modification of upstream processing steps
which are either impractical or can only be
applied in special circumstances.
For example, materials utilized for the
Nuclear Power industry carry a
recommendation for low cobalt
composition, in the case of various steels.
Stainless steel specifications do not contain
a requirement for a sufficiently low cobalt
level, so additional purchaser requirements
(beyond typical material specifications) are
necessary. The additional requirements may
force a completely separate heat at the
ingot stage of material processing to
support the specific chemistry. Most endusers
do not have volume needs that can
fully employ an ingot's worth of material.
Vintage materials
Material selection extends into product or
warranty replacement for alternate materials.
Often, vintage material may no longer be
procurable within the industry or normal
supply chain. Unavailability may drive an
engineer to undergo the material selection
phase of the design process again.
Sometimes, this process may be years or
decades in separation from the initial design
consideration. Because of the length of time,
the documentation regarding considerations
made in the first design process may not be
January 2022
19
https://saemobilus.sae.org/
SAE Update - January 2022

Table of Contents for the Digital Edition of SAE Update - January 2022
