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T6 temper 7075 has an ultimate tensile strength of 510–540 MPa (74,000–78,000 psi) and yield strength of at least 430–480 MPa (63,000–69,000 psi). It has a failure elongation of 5–11%. [9] The T6 temper is usually achieved by homogenizing the cast 7075 at 450 °C for several hours, quenching, and then ageing at 120 °C for 24 hours.
Different forms and tempers of 6061 aluminium alloy are discussed in the following standards: [28] ASTM B209: Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate; ASTM B210: Standard Specification for Aluminum and Aluminum-Alloy Drawn Seamless Tubes; ASTM B211: Standard Specification for Aluminum and Aluminum-Alloy Bar, Rod ...
The superficial Rockwell scales use lower loads and shallower impressions on brittle and very thin materials. The 45N scale employs a 45-kgf load on a diamond cone-shaped Brale indenter, and can be used on dense ceramics. The 15T scale employs a 15-kgf load on a 1 ⁄ 16-inch-diameter (1.588 mm) hardened steel ball, and can be used on sheet metal.
A variety of hardness-testing methods are available, including the Vickers, Brinell, Rockwell, Meyer and Leeb tests. Although it is impossible in many cases to give an exact conversion, it is possible to give an approximate material-specific comparison table for steels .
There are several scales of durometer, used for materials with different properties. The two most common scales, using slightly different measurement systems, are the ASTM D2240 type A and type D scales. The A scale is for softer ones, while the D scale is for harder ones. The image of Bareiss digital durometer is shown in the photo.
Two scales that measures rebound hardness are the Leeb rebound hardness test and Bennett hardness scale. Ultrasonic Contact Impedance (UCI) method determines hardness by measuring the frequency of an oscillating rod. The rod consists of a metal shaft with vibrating element and a pyramid-shaped diamond mounted on one end. [4]
Therefore hardness can be characterized at many different length scales, from hard materials like ceramics to soft materials like polymers. The earliest work was finished by Bulychev, Alekhin, Shorshorov in the 1970s, who determined that Young's modulus of a material can be determined from the slope of a force vs. displacement indentation curve ...
The hardness may also be shown as XXX HB YYD 2. The XXX is the force to apply (in kgf) on a material of type YY (5 for aluminum alloys, 10 for copper alloys, 30 for steels). Thus a typical steel hardness could be written: 250 HB 30D 2. It could be a maximum or a minimum.