An important, but difficult to quantify, property of a material.
It relates to the ease by which material can be removed from a work-piece by a cutting tool, in turning, drilling, shaping or milling, etc., to leave a satisfactory surface finish. Materials with good machinability permit fast cutting speeds, high feeds with low tool wear and produce a bright, smooth surface. Free Machining Brass CW614N (CZ121 Pb3) has one of the fastest rates of metal removal and sets the machinability standard against which the machinability of all other alloys are measured.
Malleability
The ability of a metal to deform into a useful shape, without breaking or cracking, under a compressive load. It is therefore the analogue of ductility which measures these effects in tension. A ductile material is invariably malleable and, hence, ductility and malleability are, incorrectly, often used interchangeably. Malleability is improved by annealing.
Manganese Bronze
A frequently, but incorrectly, used term to describe the duplex, high tensile, Brasses (e.g. CW721R / CZ114) that contain Manganese.
Manipulation Tests
Tests performed on full section or sector specimens to evaluate the ability of the work-piece to withstand possibly severe manipulation.
Crush, flare, bend, flare and flange, flatten, reverse flatten, reverse bend and Van Stone flange tests may be used.
Martensite
A non-equilibrium, hard, phase that can exist in some steels. It is formed if a steel with sufficient Carbon content, usually above 0.35 to 0.4%, is heated into the austenite temperature range above 760°C, held at that temperature for a period and then quenched rapidly to room temperature. The Carbon, which is present in the lower temperature ferrite phase as carbides, dissolves in the austenite and, on quenching is trapped in, and strains, the lattice increasing the hardness. This reaction is the mechanism by which all Carbon and most alloy steels are hardened.
Martensitic Stainless Steels
Martensitic grades of stainless steel are corrosion resistant, although less so than the austenitic grades, but can be hardened by heat treatment.
They are straight Chromium steels containing little or no Nickel.
They are magnetic and are mainly used where hardness, strength, and wear resistance along with corrosion resistance are required.
Typical applications include cutlery, surgical instruments, fasteners, valves, pumps, springs and components for food processing.
Matte
The mixture of Copper and Iron Sulphides produced by smelting the concentrated ore
Mean Diameter
The sum of any two diameters at right angles divided by two.
Mean Wall Thickness
For a tube this is the sum of four wall thickness measurements, made at 90o intervals around the diameter, divided by four.
Mechanical Properties
The properties of a material that reveal its elastic or plastic behaviour under an applied load. They govern its suitability for any mechanical application. The usual properties considered are modulus of elasticity, yield or 0.2%/1.0% proof strength, ultimate tensile strength, elongation and fatigue limit.
The SI unit for measuring the strength of a material and is abbreviated to MPa.
Numerically it is exactly equivalent to Newtons/square millimetre (N/mm2 or Nmm-2).
An approximate, rule of thumb, conversion to the Imperial measure of ton/in2 is: 1 ton/in2. = 15 MPa.
Melt Cast, Heat
These terms are used interchangeably to refer to the product of a single melting furnace charge. Sometimes the furnace contents are tapped into two or more ladles when the product of each ladle may be called a separate cast.
It is always assumed that the chemical composition of an entire cast will be uniform. This is described as the “cast analysis” on a Certificate of Conformity etc.