NON - FERROUS ALLOYS

Duralmin

It is one of the oldest and best known alloys of aluminium widely used for aircraft parts. Its composition is 3.5-4.5% copper, 0.4-0.7% manganese, 0.4% silicon and sometimes contain 0.4- 0.7%, magnesium and below 0.5% iron.

It developed maximum properties as a result of heat treatment and age hardening which can be worked readily about 5000C and after quenching ages over a period of 4 to 5 days. Its tensile strength increase from 1.55-1.86ton/cm2 yield point from 1.04-2.325 t/cm2 and hardness from 65 brinell to 95 brinell.

Used for highly stressed structural components, aircrafts and automobile parts like front axle, levers, bonnets, connecting rods, chassis from, girders for ships, aeroplane air screws, spares, clips, fitting, levers etc.

Also used for surgical and orthopaedics works for non magnetic and other instrument parts.

Y-alloys

Y-alloys are of the best alloys of this groups is a high strength costing alloy which retains its strength and hardness at high temperature.

Its percentage composition is 4% copper, 1.5% magnesium and 2% nickel, each of silicon, manganese is 0.6%. In the cost and heat treated from its ultimate strength is 2.12 tons/cm2 but chill costing after heat treatment show a strength of 3.1 tonnes/cm2. Heat treated forged alloys give an ultimate strength of 3.565 – 4.185 ton/cm2 an elongation of 17 – 22% and brinell hardness of 100-105.

It is extensively used for pistons, cylinder heads and crank case of internal combustion engine.

Copper alloys

(a) Copper- Aluminium alloys

Aluminium gets hardened and strengthened by the addition of copper. The most extensively used alloys for castings are those containing 4,5,7,10 and 12% of copper and with ultimate strength ranging from 1.12 – 4.185 t/cm2. It is employed in industry for light casting requiring greater strength and hardness than ordinary aluminium.

It is used for automobile piston, crank cases, cylinder heads, connecting rods.

(b) Copper-Tin

These bearing alloys containing greater proportion of tin with copper and antimony and known as white metals.

Another alloys of this type having composition of 86% tin, 10.5% antimony, 3.5% copper has a tensile strength of 0.996 t/cm2, elongation 7.1% with brinell hardness of 33.3 and compressive yield point of 4.3.

It is used in main bearings of motors and aero-engines.

(c) Babbot

It is a general white metal alloy with soft lead and tin base metals covering a range of alloy having similar characteristics varying composition. Its actual composition is 82.3% tin, 3.9% copper, 7.1% antimony.

A cheaper babbit metal used for bearings subjected to moderate pressure has composition as 59.54% tin, 2.25 to 3.75% copper, 9.5 to 11.5% antimony, 26% lead, 0.08% iron, 0.08% bismuth.

They are use as liners in bronze or steel backing and are prepared for higher speed, excellent embedability, conformability, ability to deform plastically used in IC engine bearing, general machinery purpose bearings.

(d) Phosphorous bronze

The phosphorous bronzes are the alloys of copper and tin with 0.1 to 1.5% phosphorous.

Phosphorous is added both for deoxidising the tin oxide and developing the structure and general properties of the metal. In the form of casting phosphorous bronze gives and ultimate strength of about 18 tonnes /cm2 with elongation of 4% brinell hardness number 80-100. It is used for heavy compressive loads and is used for gear wheels and slide values. Phosphorous bronze in wrought alloy form containing 10% tin, 0.1 – 0.35% phosphorous has a tensile strength 3.72 t/cm2, Bhn 100 – 130. It has good corrosion resistance to sea water and is used for spring and turbine blades.

(e) Brass

These are the alloys of copper and zinc with varying percentage of two metals. If small amount of one or more metals are added they provide more specific properties like colour, strength, ductility, machinability.

Alfa- brasses- 36% zinc and 64% cu.

Alfa Beta- brasses – 40 to 44% zn and 64 to 55% cu.

Alfa - brasses possess good tensile strength, good ductility, suitable for producing sheet, strips, tubes, wires etc.

Alfa Beta- brasses are used for hot pressings, stampings.

Copper-Nickel

Nickel forms with copper in varying properties a large number of alloys. The addition of even a small amount of nickel to copper has a marked effect upon its mechanical properties and increase its corrosion resistance.

Cupro-Nickel has a nickel content between 10 – 30% has remarkable drawing properties with tensile strength of 6.2 t/cm2 used for sheaths or envelopes of rifle bullet.

A 70/30 cupro nickel used for condenser tubes produced by extrusion process. 8 t/cm2 elastic limit, 5.9 t/cm2 ultimate strength, Bhn 140.

Predominating elements of lead alloys, zinc alloys and nickel alloys

Lead alloys

The tin is replaced by lead base alloys and contains 10 – 15% antimony, 15% Cu, 20% Tin and 60% Lead. These alloys are cheaper than tin base alloys, but not strong and do not possess the lead carrying capacity strength decreases with increasing in temperature. An alloy containing 80% lead, 15% antimony and 5% tin or 20% antimony generally used for long bearings with medium loads.

Binary copper lead alloys- lead 10 – 20%, 20 – 30% and above 30%.

Zinc alloys

These alloys used in the form of tooling plate and easy and speed of fabrication.

Brasses – Alloys of Cu and Zn.

Nickel alloys

Nickel is one of the most important metals which is used as a pure metal and alloyed with other elements.

Nickel copper, nickel copper silicon alloys.

Nickel copper tin, sometimes with lead.

Nickel chromium- with iron or cobalt.

Nickel molybdenum-also with chromium.

Nickel silicon.

Nickel manganese, nickel aluminium.

Low alloy materials like P-91, P-22 for power plants and other high temperature services, high alloy materials like stainless steel grades of duplex, stiper duplex materials

Low alloy materials

Which possess slowly cooled micro structures, similar to those of plain carbon steel in the same condition namely pearlite, pearlite plus ferrite. These low alloy also known as pearlite alloy steel.

High alloy steel

Which possess slowly cooled micro structure, consisting either of martensite, austenite or ferrite plus carbide particle. It is more than 8% in the case of steels.

NON - FERROUS ALLOYS