Be from Aluminum deep processing
Effect of heat treatment on aluminum and its alloys
Aluminum and aluminum alloy materials are heated to a certain temperature and held for a certain time to obtain the desired product structure and properties.
Main heat treatment methods and basic action principle of aluminum and its alloys
I. Classification of heat treatment of aluminum and aluminum alloys (as shown below)
2.aluminum and aluminum alloy heat treatment basic action principle
Annealing: the product is heated to a certain temperature and held for a certain time, then cooled to room temperature at a certain cooling rate. Through atomic diffusion and migration, the structure is more uniform and stable, and the internal stress is eliminated, which can greatly improve the plasticity of the material, but the strength will be reduced.
(1) Ingot homogenization annealing: long-term heat preservation at high temperature, and then at a certain speed (high, medium, low, slow) cooling, the ingot chemical composition, structure and performance homogenization, can improve the material plasticity about 20%, reduce extrusion pressure about 20%, improve extrusion speed about 15%, at the same time improve the quality of material surface treatment.
(2) Intermediate annealing: also known as local annealing or annealing between processes, is to improve the plasticity of the material, eliminate the internal processing stress of the material, and keep the heat at a lower temperature for a shorter time, in order to facilitate continuous processing or obtain a combination of some properties.
(3) Complete annealing: also known as finished product annealing, is at a higher temperature, heat preservation for a certain time, in order to obtain complete recrystallization of the softening structure, with the best plasticity and low strength.
Solution quenching treatment: Will be strengthening heat treatment of aluminum alloy material is heated to high temperature and maintain a certain amount of time, make the material of the second phase or other soluble component dissolves into the aluminum substrate, form the supersaturated solid solution, and then to fast cooling method to keep the supersaturated solid solution to room temperature, it is a state of instability, because in the high energy state, the solute atoms could precipitate. But at this time the material plasticity is high, can be cold working or straightening process.
(1) online quenching: for some alloy materials with low quenching sensitivity, can be used for solution at high temperature during extrusion, and then quenched with air cooling (T5) or water spray cooling (T6) to obtain certain microstructure and properties.
(2) offline quenching: for some of the quench sensitivity high alloy materials must be in a special heat treatment furnace heated to a high temperature and heat preservation time, and then transfer to no more than 15 seconds of time quenching in water or oil, in order to obtain a certain organization and performance, depending on the equipment can be divided into salt bath quenching, quenching air, vertical quenching, horizontal quenching.
Aging: after the solid solution quenching of the material, at room temperature or higher temperature for a period of time, the unstable supersaturated solid solution will be decomposed, and the second phase particles will precipitate (or precipitate) from the supersaturated solid solution, distributed around the α (AL) aluminum grain, thus producing a strengthening effect called precipitation (precipitation) strengthening.
1. Natural aging: Some alloys (such as 2024, etc.) can produce precipitation strengthening at room temperature, which is called natural aging.
2.Artificial aging: Some alloys (such as 7075, etc.) have obvious precipitation strengthening effect at room temperature but obvious precipitation strengthening effect at higher temperature, which is called artificial aging. Artificial aging: Some alloys (such as 7075, etc.) have obvious precipitation strengthening effect at room temperature but obvious precipitation strengthening effect at higher temperature, which is called artificial aging.
Artificial aging can be divided into under aging and over aging.
① Underaging: In order to obtain certain properties, lower aging temperature and shorter aging time should be controlled.
② Over-aging: aging at a higher temperature or for a longer time in order to obtain some special properties and better comprehensive properties.
③ Multi-stage aging: In order to obtain some special properties and good comprehensive properties, the aging process is divided into several stages. It can be divided into two-stage and three-stage aging
Regression treatment: In order to improve the plasticity, facilitate cold bending forming or correct the tolerance of form and position, the products that have been quenched and aged can be heated at high temperature for a short time and then returned to the new quenched state, which is called regression treatment.