Each field has its own terminology, and aluminum alloys are no exception. Many friends have recently reported to us that some basic terms of materials are difficult to understand. Today PTJ will give you a brief introduction to 8 Basic terms:1.Strength and yield strength
Strength is the ability of metallic materials to resist permanent deformation and fracture under external forces. The indicators commonly used in engineering to indicate the strength of metal materials are yield strength and tensile strength. Yield strength is the yield limit when a metal material undergoes a yield phenomenon, that is, the stress resisting a small amount of plastic deformation.
The elongation mainly measures the plastic properties of the material, that is, the performance of permanent deformation without breaking.
The ability of a metal material to resist other harder objects being pressed into the surface is called hardness, or the material’s resistance to local plastic deformation. Therefore, there is a certain relationship between hardness and strength. According to the hardness measurement method, the most commonly used hardness values are:
(1) Brinell hardness (code HB);
(2) Rockwell hardness (HRC; HRB) between Rockwell hardness HRC and Brinell hardness HB: 1HRC≈0.1 HB.
Under long-term repeated stress or alternating stress (stress is generally less than the yield limit strength δS), the phenomenon that fracture occurs after significant deformation is called fatigue failure or fatigue fracture.
The force on a unit cross-sectional area inside an object is called stress. The stress caused by the external force is called the working stress, and the stress that is balanced inside the object without the external force is called the internal stress (such as tissue stress, thermal stress, residual stress remaining after the machining process, etc …).
6.Stress relief annealing
Stress relief annealing is also called low temperature annealing (or high temperature tempering). This annealing is mainly used to eliminate residual stresses in castings, forgings, welded parts, hot rolled parts, cold drawn parts, etc. If these stresses are not eliminated, the material will cause deformation or cracks after a certain period of time or during subsequent cutting processes.
7.Solid solution heat treatment
The alloy is heated to a high temperature in the single-phase region and maintained at a constant temperature, so that the excess phase is fully dissolved in the solid solution, and then rapidly cooled to obtain a heat treatment process of supersaturated solid solution. Purpose: To fully dissolve various phases in the alloy, strengthen solid solution, improve toughness and corrosion resistance, eliminate stress and soften, so as to continue machining or forming.
A metal heat treatment process that places the quenched metal workpiece at room temperature or a higher temperature for an appropriate time to improve the strength of the metal. The aging treatment performed at room temperature is natural aging; the aging treatment performed at higher temperatures is artificial aging. In mechanical production, in order to stabilize the size of the casting, the casting is often left at room temperature for a long time before cutting. This measure is also called aging. But this aging is not a metal heat treatment process.