TZM Molybdenum Alloy

Recrystallisation & hot strength

Metallurgical condition as supplied Required by the standard

Unless the order states otherwise, material is supplied wrought and stress relieved (SR).

SR = stress-relieved, RX = essentially fully recrystallized. TZM covers Material 363 (vacuum arc melted) and 364 (powder metallurgy); the two carry identical composition, mechanical and reheat-test requirements and differ only in the melting route.

Stress-relieved versus recrystallised Required by the standard

On recrystallisation TZM's yield falls from 585 to 380 MPa (about -35%) and its tensile from 690 to 550 (about -20%). The proportional loss is smaller than pure molybdenum's (-47% on yield), but note the absolute figures: recrystallised TZM at 380 MPa is still below stress-relieved pure molybdenum at 450 MPa in the same diameter band. TZM's value is therefore not that it stays stronger after recrystallising, but that it recrystallises later - see the thermal-stability row below, where TZM is reheat-tested at 1150 °C against 900 °C for pure molybdenum.

⚠ The two diameter bands do not line up exactly (SR is 1.125-1.875 in, RX is under 2 in), so read the pair as the same size class.

Thermal-stability reheat test Required by the standard, conditionally

This row is the reason TZM exists: the reheat test temperature is 1150 °C for TZM (363/364) against 900 °C for pure molybdenum (360/361) — 250 °C higher. The criterion in both cases is that the material still meets the tensile minima after 30 min of reheating.

⚠ The test is performed only if the purchase order specifies it. If the order is silent the test is not run and the certificate will not carry it; writing the requirement into the order is what turns that 250 °C into an acceptance commitment.

The reduced temperature for small rounds (850 °C at ≤47.6 mm) applies to 360, 361 and 365 only — not 363 or 364, so TZM is tested at 1150 °C in every size.

Protective annealing atmosphere Required by the standard

Not permitted — Nitrogen is not an acceptable atmosphere for annealing molybdenum or molybdenum alloys.

⚠ Nitrogen may not be used to anneal molybdenum or its alloys: at temperature it forms nitrides and embrittles the surface. TZM, which carries titanium and zirconium, is if anything more atmosphere-sensitive, and the ban applies to it equally.

All four acceptable atmospheres carry a purity threshold (5 ppm oxygen for argon and helium, 0.0133 Pa for vacuum, ≤0 °C dew point for hydrogen); an atmosphere that misses it is not protective.

Chemical composition

Nominal: mid-range where both limits are given, the cap where only a maximum is, balance takes the remainder. Exact specified ranges below.

Mechanical minima by form

Guaranteed values differ by form, size and delivery condition; quotations confirm the specification, form, size and condition.

Where this grade is recommended

Matched in 8 service conditions; ranks and scores computed from the condition-scoring matrix.

Designations & equivalents

Cross-references are common near-equivalents for search and shortlisting; substitution across standards requires clause-by-clause verification. All grades in one cross-reference table →

Applicable standards

Name the standard and its edition on the order.

Frequently asked questions

Same series

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Supply & enquiry

Tube & pipeφ1 – 219 × 0.25 – 25 mmPlate4.76 – 80 mmBarφ8 – 300 mmWire & filler metalsφ0.01 – 8 mm