Aerospace Solutions: A Guide to Material Selection, Verification, and Change Control

What Does an Aerospace Materials Solution Actually Solve?

Buyers may need to reduce part mass, survive elevated temperatures, resist corrosion, manage fatigue risk, retain traceability, qualify a process, or keep a released configuration unchanged. An alloy family, by itself, doesn’t directly address these needs. A buyer looking for a solution to these needs would need to define the requirement, restrict the scope of the material to be considered, provide evidence, and make an authorization decision to release the material.

This distinction is practical. The FAA’s active AC 20-154A addresses receiving-inspection system development and traceability, but it’s non-mandatory guidance and describes one acceptable approach. Meanwhile, 14 CFR 21.137 sets quality-system requirements for production-certificate applicants and holders. Neither source should be turned into a universal supplier checklist. The governing design data, contract, customer flowdowns, approval basis and assigned authorities determine what applies.

This approach prohibits the use of a default or simplified approach, i.e. “usually we use this alloy family” or “usually we use this grade.” Each rung of the ladder provides an input for the next rung. If the service condition is undefined, screening isn’t defined. If the controlled definition isn’t complete, test results can’t verify the intended condition. If the decision authority isn’t named, an exception can be given and circulated to other persons without a legitimate disposition.

Start With the Service Envelope, Not an Alloy Name

Criteria for material selection shouldn’t be defined by preference, but rather by the conditions of the application. Those conditions should be defined in terms of load (type, magnitude, location and direction), frequency and duration, operating and transient temperatures, thermal gradients, pressures, vibration and contact stresses, and expected life. The chemical and physical conditions of the environment should also be defined. Those conditions might include humidity, corrosive gases, fuels and lubricants, cleaning agents, radiation, vacuum, or products of combustion.

As part of defining the environmental envelope, manufacturing can also be defined. The way a product is formed and finished can also affect the delivered condition and the evidence needed to accept it. The AMPP materials-selection overview makes the basic point that there’s no material that resists all corrosive conditions. The balance of available information and expected life should also be part of the selection consideration.

The consequence of a wrong assumption helps the assigned authorities decide how much evidence and control the application requires. Ask whether a failure could affect finish, replaceability, system availability, flight safety or regulatory obligations, then identify who owns the design requirement, special-process decision and release decision. This is a scoping exercise, not a universal rule for prototypes, ground support or flight hardware.

A public reference document shouldn’t be designed to be used as a design-allowable material document. The output at this stage should be a bounded problem statement that describes the expected service, service life, geometry, manufacturing route, inspection, consequences of failure, and program constraints. The statement should also define the overall constraints of the program. Engineering teams can use these constraints to screen candidate materials against the same questions used across the wider aviation industry.

How Should You Screen Aerospace Material Families?

Titanium alloys, nickel alloys and stainless steels may enter an aerospace screening exercise, but no family wins through a generic property ranking. Compare candidates under the same product form, supplied condition, manufacturing route, temperature, environment and test basis. Evidence for one form or process shouldn’t be treated as evidence for a different form or route without an authorized technical basis.

Evidence specific to a process isn’t academic. For example, in a study of Ti-6Al-4V performed by NIST, using electron beam melting, it was reported that fatigue limit stress was in the range of 200-250 MPa under specified test conditions and fatigue cracks were initiated from lack of fusion. That value doesn’t define a design allowable. It illustrates that process conditions and the population of defects can affect performance, even if the alloy remains the same.

Family screening should produce a short list and a visible set of unanswered questions. A possible mass, temperature or corrosion benefit doesn’t close the decision if joining, inspection, supplied condition, form, route or evidence remains unresolved. Keep those gaps open until the assigned engineering and quality authorities define the acceptance basis.

Translate the Design Requirement Into a Controlled Material Definition

The name of a grade is an initial identification, not a complete purchasing definition. The controlled definition should name the material designation, product form, condition and route, the specification and revision, dimensions, tolerances, surface condition and treatment, required tests, marking and record evidence, and any special clauses concerning source and approval.

Public standards records identify the boundary. For example, SAE AMS4928X references specific product forms of Ti-6Al-4V as well as an annealed condition under a specific revision. The designation “Ti-6Al-4V” doesn’t mean every form, condition, dimension, test, or route covered (or not covered) by that record. The current purchase document and licensed standard text remain controlling.

A compact definition template

Record the governing source, unit system, test conditions and authorized conversion method whenever values are compared. A converted number isn’t an aerospace limit, design input or substitute test basis unless the governing requirement says so.

Keep the supplying legal entity and processing sites identifiable. A coordinated supply network or listed capability shouldn’t be treated as proof that every operation is performed in-house for every order. The purchase requirement, route and records should identify who performed the work for the delivered lot.

Which Claim Does Each Document Actually Support?

Documents are useful when they’re associated with a specific claim because identity tells the buyer what the item is, while the remaining layers address conformance, qualification, and authorization for use. One recurring error is treating identity, conformance, qualification, and program approval as synonyms. They’re different layers with different decision owners.

NIST’s overview of additive manufacturing qualification describes the qualification of the material, the process, and the part. The same overview notes that historical empirical programs can involve thousands of tests and take 5–15 years. These examples are illustrative and not prescriptive of required or normal commercial lead times. Their value here is conceptual: a grade name and one certificate can’t stand in for a qualification basis that includes process and part behavior.

The integrity of evidence is as important as the presence of a document. According to NASA, two Taurus XL missions worth more than $700 million were lost because of faulty material and falsified certifications. This case doesn’t mean that every certificate is unreliable; it shows why traceability and test evidence must reconcile to the physical item and trustworthy source data.

“NASA relies on the integrity of our industry throughout the supply chain.”

NASA investigation statement

Keep Evidence and Physical Condition Continuous Through Every Handoff

The absence of traceability means that records no longer point to the same controlled object. It may begin with a heat, lot, or batch and continue through receipt, storage, cutting, outside processing, inspection, repackaging, and release. Each split, merge, relabel, or status change needs a reconciliation point appropriate to the program.

The qualification of a process also deserves special consideration. Heat treatment, welding, coating, NDE, and additive manufacturing may require qualified procedures, personnel and equipment, plus in-process evidence. Evidence of receipt can’t prove the qualified condition of an uncontrolled furnace cycle, weld parameter, or inspection method.

Physical preservation is equally important. Proper documentation can’t undo damage from mishandling, corrosion, contamination, foreign-object debris, expired preservation, and broken packaging. 14 CFR 21.137, in the context of a production certificate, outlines procedures for handling and storage to prevent damage and deterioration and includes quality-record controls. In other contexts, use the applicable contract, specification, and approved system, rather than borrow a retention period or preservation limit from an unrelated program.

How Should Supplier-System Evidence Be Read?

Treat supplier-system evidence and order evidence as separate review layers. For any certificate presented, verify the named legal entity, site, stated scope, standard, revision, status and issuing body from the applicable authoritative record. Then review customer approvals, approved-source requirements, special-process sources and order-specific flowdowns on their own evidence.

The IAQG Supply Chain Management Handbook’s “Buy” resources discuss supplier capability assessment, flowdown, verification, monitoring and sub-tier control from a buyer-side perspective. These are guidance and assessment resources. Using SCMH, SCA or AIMM doesn’t certify a supplier, and mentioning 9100- or 9120-series systems doesn’t prove that TiAlloy, or any named organization, holds a current certificate.

This authority map keeps organization-level assurance, order conformance and program approval as separate questions. The applicable contract, approved procedures and assigned roles determine how the answers connect for a specific order.

Control Substitutions and Revisions Before They Break the Evidence Chain

A substitution is a proposal for review, not automatic interchange. Factors such as similar chemistry, higher strength, a newer process, or lower cost don’t resolve behavior, form, condition, microstructure, defects, inspection, configuration, or approval issues. For example, an alloy substitution described by NASA in a lesson learned from a flight assessment showed directional behavior and fit-up stresses from other features contributing to cracking. An alloy substitution could have consequences beyond the material of concern.

Identify affected requirements first for any changes. These include source and melt/heat, machine or software, parameter sets, tooling, heat treatment, finishing, inspection, site, and sub-tier. Next, determine who will make the decision, what equivalence or requalification evidence is required, and how records and configuration data will be updated before release.

NIST’s qualification work provides an example of why a “minor” process change can be consequential in an empirical qualification context. The response, however, isn’t to demand full requalification for every clerical revision. It’s to avoid assuming the change is benign before the responsible authority evaluates its scope. Where the customer or program flows down work-transfer, APQP, PPAP, or other planning requirements, map the applicable deliverables and approval gates. Through these, define requirements for work approval before changing source, site, process, or sub-tier. They don’t necessarily apply to every metal purchase order.

What Should Happen When the Evidence Does Not Reconcile?

A mismatch can’t be fixed through editing a certificate, guessing a missing condition or choosing the nearest entry in a catalog. First, correctly identify the discrepancy. Examples include wrong revision, missing heat number, discrepancy in quantity, missing test value, unapproved processor, broken marking, damaged package, or an item that doesn’t conform to the documentation.

1. Protect status. Make the hold visible in the applicable physical and electronic controls defined by the approved procedure.
2. Segregate when required. Preserve the identity and condition of the material while avoiding mix-ups, contamination, or further processing.
3. Document the facts. Be factual and accurate. State explicitly the requirement, observed evidence, identity of the affected item or lot, and affected quantity without inventing a cause.
4. Route evaluation. Forward the case to the appropriate authority defined in the approved quality, design and contract system for a decision.
5. Record the disposition. Implement only the authorized disposition, reconcile the affected records and complete any recurrence action required by the approved procedure.

According to its stated scope, 14 CFR 21.137 calls for the identification, documentation, evaluation, segregation and disposal of nonconforming items through approved procedures. This pattern of control is useful, but public articles can’t authorize “use as is,” repair, rework, return or scrap for a reader’s program. The approved procedures and assigned roles control.

Evidence gaps may also show a larger escape. If the same heat was split, processed, or shipped to some other location, retain the genealogy needed for an impact review. The objective isn’t to fill a single missing field. It’s to understand the physical material, the processes, records and downstream choices affected.

An Adaptable Evidence-Readiness Review

This review is a planning aid, not a universal aerospace assurance or release model. IAQG’s Plan and Manage resources provide broader buyer-side planning context. Use the prompts only to expose missing inputs and route them to the authority named by the applicable contract, design data and approved procedures. Completing the table never makes a material “aerospace approved.”

Use these prompts before quotation or release only as an input check. The governing program and assigned authorities still decide what evidence is sufficient and who may act. Once the engineering and evidence questions are bounded, product-form requests and order-specific supply discussions can move to the commercial channel.

Frequently Asked Questions