Permalloy 80 Super Alloy

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication and Heat Treatment
     Machinability
     Forming
     Heat Treatment
     Welding
     Cold Working
     Hardening
Applications

Introduction

Permalloy was primarily developed in the early 20th century for inductive compensation of telegraph cables. Permalloy is known for its very high magnetic permeability, which makes it useful as a magnetic core material in electrical and electronic equipment. The other key magnetic properties it possesses are near zero magnetostriction, low coercivity, and anisotropic magnetoresistance.

Super alloy Permalloy 80 is a high magnetic permeability alloy of nickel and iron.

The following sections will discuss in detail about super alloy Permalloy 80.

Chemical Composition

The chemical composition of Permalloy 80 is outlined in the following table.

Element Content (%)
Nickel, Ni 80.2
Iron, Fe 14
Molybdenum, Mo 4.85
Manganese, Mn 0.5
Silicon, Si 0.3
Chromium, Cr ≤ 0.020
Cobalt, Co ≤ 0.020
Carbon, C 0.015
Aluminum, Al ≤ 0.010
Phosphorus, P ≤ 0.0050
Sulfur, S ≤ 0.0010

Physical Properties

The physical properties of Permalloy 80 are tabulated below.

Properties Metric Imperial
Density 8.7 g/cm3 0.316 lb/in3
Melting point 1454°C 2650°F

Mechanical Properties

The following table shows mechanical properties of annealed Permalloy 80.

Properties Metric Imperial
Tensile strength 682 MPa 98900 psi
Yield strength 338 MPa 49000 psi
Elongation at break 32% 32%
Hardness, Rockwell B 80 80

Other Designations

Equivalent materials to Permalloy 80 are ASTM A753 ALLOY 4 and MIL N-14411 Comp 1.

Fabrication and Heat Treatment

Machinability

Super alloy Permalloy 80 can be machined using the common processes. The high nickel content in this alloy causes "gumminess" while machining. It displays the same characteristics as the 300 series austenitic stainless steels. It is recommended that high-speed steel or carbide tools be used along with lard oil lubricant. When using water-soluble cutting fluids care should be taken to immediately clean the parts thoroughly after machining so as to avoid corrosion contamination.

Forming

Super alloy Permalloy 80 can be formed using any of the conventional methods.

Heat Treatment

Permalloy 80 not hardenable by heat treatment. Annealing can be performed in a dry hydrogen atmosphere at 1176°C (2150° F) for 4 h, followed by furnace cooling to 593°C (1100°F), and then a cooling rate of 260°C (500°F)/ h from 593 to 372°C (1100 to 700°F). Air cooling should be done to 372°C (700°F). Strain relief annealing can be performed at 927°C (1700°F) for 1/2 h in a dry hydrogen or inert gas atmosphere.

Welding

Welding of super alloy Permalloy 80 can be performed using all the traditional welding methods.

Cold Working

Permalloy 80 has good ductility and is readily cold formed.

Hardening

Super alloy Permalloy 80 hardens only by cold work.

Applications

Permalloy 80 is chiefly used found in transformer core laminations and magnetic shielding.

Comments

  1. Joe Schmoe Joe Schmoe United States says:

    I noticed electrical conductivity was not mentioned.  Do you have that data?

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