Hardness and Conductivity Al-Alloys

[Dan320]

I'm working with company procedures for heat treating al-alloys. To begin with, we were mainly concerned with MD-80s and used that SRM for information. Now we want to be able to heat treat parts for Boeings and Airbuses. To our surprise we find different hardness and conductivity values in the various SRMs and associated standards for the same alloy.
In some cases the difference may be so great that a part which is ok for one a/c would be scrap for another a/c.
Anyone with similar experience?

 

[WKTaylor]

Dan320...

CAUTION.
You have "NO say" as to which hardness and conductivity values are valid: The specified heat treat process [MIL, AMS, BAC, DPS, etc] WILL define which conductivity and hardness values are to be used. NOTE. IF this requirement is for a "special inspection" [heat damage, material segregation, etc], then the SRM, T.O., AD, etc must state which values are valid [table, spec, etc].

For instance...

AMS2770 "Heat Treatment of Wrought Aluminum Alloy Parts" explicitly refers to AMS2658 "Hardness and Conductivity Inspection of Wrought Aluminum Alloy Parts".

MIL-H-6088 and AMS-H-6088 "HEAT TREATMENT OF ALUMINUM ALLOYS" have their own tables for hardness and conductivity.

BAC5602 "HEAT TREATMENT OF ALUMINUM ALLOYS" Explicitly refers to BAC5946 "Temper Inspection of Aluminum Alloys".

MDC PS15701 GENERAL HEAT TREATING CRITERIA FOR ALUMINUM ALLOYS DOUGLAS COMMERCIAL AND C-17 AIRCRAFT) specifies PS23023 "HARDNESS AND ELECTRICAL CONDUCTIVITY INSPECTION ACCEPTANCE CRITERIA FOR METALS".

The reason for this explicit statement is both simple and complex: the details within the HT spec, and the materials heat treated [AMS, MIL, BMS, DPS, etc], VARY... and each HT spec takes it's unique variables into consideration.

NOTE. Design manual allowables are built based on the alloys, HTed per an explicit of implicit specification.

IE: MMPDS allowables are only given [developed] for AMS or MIL [now ASTM] spec controlled materials, which are heat treated per an industry heat treat standard... or as specifically stated within the material specification.

On the other hand, Boeing and Douglas have design allowable handbooks where AMS, MIL and corporate spec materials are heat treated per the corporate HT spec... or as specifically stated within the material specification. In some cases, there are significant differences in the final product between MMPDS and the corporate design manuals… and this is usually noticed in the HT NDT results being significantly different for the “same” [NOT] material and HT/temper… and/or varying temper categories.

Regards, Wil Taylor

 

[Dan320]

Thanks Wil, I will read your post carefully and thoroughly.
Thanks again.
Dan