6AL-2SN – 4ZR-2MO

Principal Design Features

This near alpha alloy is designed primarily for high temperature applications (up to 538 C). It combines excellent strength and corrosion resistance with relatively good weld and fabricability. Beta Transus (F +/- 25) 1820.

Applications

Most commonly found in gas turbine compressor components, such as blades, discs and impellers. It is also used for sheet metal components in afterburners and “hot” airframe sections.

Machinability

As a family, titanium and its alloys have developed a mystique as a nightmare to machine. This is simply not the case. Experienced operators have compared its characteristics to those found in 316 stainless steel. Recommended practice includes high coolant flow(to offset the material’s low thermal conductivity), slow speeds and relatively high feed rates. Tooling should be tungsten carbide designations C1-C4 or cobalt type high speed tools.

Forming

This alloy can be hot or cold formed and will exhibit characteristics equivalent to those found in a 1/8 to 1/4 hard austenitic stainless steel.

Welding

Rated as “fair” in terms of weldability.

Heat Treatment

Beta minus 14 C(25 F).

Forging

Rough forge at 1038-1066 C(1929-1980 F), finish at 954-982 C(1770-1825 F).

Hot Working

Hot forming will reduce both the springback and required forming forces, and will increase the overall ductility of the material.

Cold Working

The cold working characteristics of this alloy are similar to those found in austenitic stainless steels. In multiple forming operations, intermediate stress relieving is recommended to offset the alloy’s tendency to work harden. Post-work annealing is re

Annealing

For duplex annealing, hold at 900 C(1670 F) for 1/2 hour, air cool to 788 C(1465 F) and air cool. For beta anneal, hold at 1024 C(1900 F) for 1/2 hour, air cool to 593 C(1100 F) for 8 hours and air cool.