The phenomenon that the strength and hardness of the quenched aluminum alloy significantly increases with the passage of time is called aging, and the age hardening of the aluminum alloy is also called. This is one of the important methods for strengthening aluminum alloys.

According to the definition, the premise of the aging strengthening of aluminum alloys is to first perform quenching to obtain a saturated single-phase structure. In a solid solution obtained by quench hardening, not only is the solute atom supersaturated, but also the vacancy (crystal point defect) is supersaturated, ie, in a double supersaturated state. The study shows that the higher the temperature of aluminum alloy solution treatment, the greater the degree of supersaturation after treatment, and the greater the effect of aging hardening after aging. Therefore, the principle of solution temperature selection is: In the premise of ensuring that the alloy does not burn, the solution temperature is increased as much as possible.

Solution-treated aluminum alloys undergo an aging process when they are left at room temperature or at a certain temperature. This process is essentially the process of precipitation of the second phase from the supersaturated solid solution. This process is carried out by shaping and growth and is a diffusion-type solid phase transition. It proceeds in the following order: What are the factors affecting the age-strengthening effect in a → GP → θ'' phase → θ' → θ phase?

Aging is carried out in a certain order, and the enhancement effect is affected by the following factors.

(1) Aging temperature. Fixed aging time, the relationship between aging temperature and aging strengthening effect (hardness) for the same composition of the alloy. At a certain aging temperature, a large hardening effect can be obtained. This temperature is called the preferred aging temperature. The ageing temperature of the different compositional alloys for obtaining a greater aging strengthening effect is different. Statistics show that the following relationship exists between the preferred aging temperature and the melting point of the alloy: T0 = (0.5 - 0.6)T
(2) The aging time. The peaks of hardness and strength appear at the end of the phase θ′′ and the initial phase of the θ′ transition phase. After the phase θ′ has elapsed, the softening begins. When a large number of θ phases occur, softening is already severe. Therefore, within a certain aging temperature, in order to obtain a larger aging strengthening effect, there should be a better aging time, that is, the time required for the transition from θ′′ to θ′.

(3) Quenching temperature, quenching and cooling speed and quenching transfer time. Practice has proved that the higher the quenching temperature, the faster the quenching cooling rate, the shorter the intermediate time of quenching, the greater the degree of supersaturation of the obtained solid solution, and the greater the strengthening effect after aging.

(4) Aging process. Aging can choose single-stage or graded aging. Single-stage aging refers to an aging process conducted at or below 100°C. The process is simple, but the uniformity of the structure is poor, and the tensile strength, yield strength, conditional yield strength, fracture resistance, stress corrosion resistance performance are difficult to get a good match. Fractionation aging is performed twice at different temperatures or multiple aging. Pre-aging at lower temperatures aims at obtaining a high density of GP zones in the alloy, since the GP zone is usually uniformly nucleated when it reaches a certain size. Models, commissions, 岣 岣 岣 橹 橹 橹 橹 木 木 木 木 木 木 谏 呶 呶 忠 忠 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 捎谖 ? ? ? ? ? ? ? ? ? ? ?龃螅 龃螅 仕 仕 仕 仕 仕 仕 仕 仕 仕 仕 仕 仕 仕 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 妒毙 砗蟮暮 砗蟮暮 砗蟮暮 砗蟮暮 砗蟮暮 砗蟮暮 涠 涠 涠 涠 涠 涠 涠 涠 涠 涠 涠 涠 涠 涠 涠 8 8 8 8 Scale? Onion Yu? Pyridium 擞? Ω? Pure 沽Α? / P>

Homogenization:

Homogenization treatment has been widely used as a means to improve the metallurgical quality and extrusion performance of the ingot. Homogenization treatment of important parameters such as: soaking time, soaking temperature and cooling rate have a clear reference. The batch-type homogenization furnace is also replaced by a continuous homogenization furnace. The continuous homogenization furnace has an advanced control system, a complete automatic detection system, a sawing and loading system. Of course, the cost of this process is quite high, and the quantitative benefits will be reduced.

Adaptability of ununiformized ingots:

However, the importance of aluminum rod heating has also been widely recognized, and the potential benefits of homogenization may be replaced by improved heating process practices. Directly heated ingots are believed to cause die defects and tears that limit the increase in extrusion speed. The exact mechanism for this situation is not clear. The phase, shape, and solid solubility between metals all affect the extrusion performance and mechanical properties of the alloy.

In recent years, it has become apparent that the high solid solubility of silicon and silicon is a very important factor for alloys. Performance, as long as the medium heating temperature may be achieved. Because the longer heating time requires only a lower temperature. T1, T5 hardness is very close to the larger value (but if compared with the performance of T4, T6 state).

The non-homogenized ingots were extruded at low temperature and without holding time (0 hour/480°C heating conditions), which was unfavorable for the performance of the extruded product T5. However, its performance can still reach the lower limit of the standard. Dent-free impact performance will also be reduced, however, we were surprised to find that its dented impact performance was higher than that of extruded products under higher heating conditions.

If needed, using rapid extrusion and standard solution and aging treatments, the product's hardness and tensile properties can be increased to that of extruded products under higher heating conditions. It may be possible to increase the performance of the inhomogeneously processed billet extrusion product T1, T5 by increasing the extrusion temperature, however, a higher extrusion exit temperature will limit the possibility of a larger extrusion speed.

It seems that the usual gas furnace has a reasonable length of hot zone for various heating of the 6063 alloy ingot. If a higher heating temperature is needed to optimize the performance of the alloy, such an aluminum rod heating furnace can meet the requirements of the heating of the billet before extrusion and form a temperature gradient. This method can be used to adapt to the processing of non-homogenized ingots.

The use of low-temperature heating or short-term heat addition means that the Fe-containing intermetallic phase does not completely convert into the equilibrium phase α-Al8Fe2Si, and its impact on strength and impact resistance has been studied, which may also affect the extrusion performance. For example, the size, shape, and type of intermetallic compounds may affect mold wear and sticky aluminum. If Mg and Si are not completely solid-solved, the remaining Mg2Si/Si will have a negative effect on the extrusion speed due to melting and tearing of the low eutectic compound. It may not be found at work that the heating conditions have no obvious effect on the breakthrough pressure and the surface of the extruded product.

Another factor that must be considered is the alloy composition. Therefore, higher heating temperatures and heating times are required. Changing the content of Mg and Si will directly affect the properties of the alloy and indirectly affect the solution temperature of the alloy. In addition, different Fe contents react with different amounts of Si, which affects the final performance of the product.

Observations:

The solution temperature of the alloy is a very important parameter for the homogenization, heating of the billet, extrusion (relative to the outlet temperature) and solution treatment. A number of techniques (processes) were used: hardness, microscopic analysis, microprobe topography, (thermocouple) to evaluate billet heating. The experimental results show that the 6063 alloy solution temperature is about 490 °C.

Ingot heating process, the composition of Fe-containing intermetallic compounds are largely dependent on the heating temperature, calculate the equilibrium phase α-Al8Fe2Si is the only phase of the 6063 alloy after 570 °C 2 hours heat preservation, but at 540 °C and more More than one intermetallic compound was found at low temperatures.

Although the use of non-uniform treatment of aluminum rods results in a reduction in hardness, tensile strength, and dent-free collision energy in the T5 state, the mechanical properties of the alloy can still be achieved. When the heating conditions are close to that of the conventional homogenization treatment, its performance reaches a high value. The indented impact energy in the state of the ingot T5 using the non-homogeneous treatment and the tensile properties of the T6 state are adversely affected. The impact on extrusion performance needs further quantification.

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