SMM9 March 18: at the 2020 (2nd) China Industry Expo New Materials Forum-China Automotive New Materials Application Summit held by SMM, and China (8th) Aluminum processing Industry chain supply and demand Trading Summit, and China (second) Copper processing Industry chain supply and demand Trading Summit, Shandong University Liu Xiangfa gave a detailed explanation on TCB crystal seed alloy and its application technology in high-strength aluminum alloy on the spot.
one。 High-strength super-high-strength aluminum alloy has a broad application prospect, but its development has encountered technical bottlenecks.
Application of High strength and Super High strength (UHS) Aluminum Alloy
UHS aluminum alloy (abbreviated as high-strength and ultra-high-strength aluminum alloy, including Zn, Zr, Si, Cu, Mg, Cr, V, etc.) has a broad application prospect in aerospace, transportation, national defense and 5G communications because of its strength advantages. However, the poor plasticity and toughness and processability have become the bottleneck restricting its development.
Casting Technical bottleneck in the Development and Application of UHS Aluminum Alloy
7xxx and 2xxx aluminum alloys lead to refinement poisoning due to Zr, Cr, V, etc., resulting in coarse grains of DC billets; resulting in segregation, shrinkage, hot cracking, casting rod cracking, accompanied by feathery crystals, bright crystals, inhomogeneous structure and other defects; coarse grains also increase anisotropy, poor deformability, high scrap rate and unstable quality.
Due to the poisoning of refinement caused by Si element in Al-Si alloys, the α-Al dendrites or eutectic clusters are unusually thick, which brings many problems, such as composition segregation, snowflake spots, shrinkage porosity, porosity and so on, which significantly reduces the strength and toughness, fatigue properties, microstructure compactness, microstructure uniformity and product consistency of castings.
In addition, there are the poisoning phenomenon of refinement of UHS aluminum alloy, the effect of α-Al grain on UHS aluminum alloy and so on.
two。 Development of TCB seed alloy
Based on the close combination of industry, university and research, starting from revealing the mechanism of nucleation poisoning and turning the evolution of molten clusters into a breakthrough, TCB crystal seed alloy was invented and developed, the direct nucleation of crystal seed was realized, the source of poisoning was eliminated, and the fine grain strengthening of aluminum alloy was realized stably.
After 17 years of technical research, a poison-resistant crystal seed alloy containing high temperature stable core-shell TCB has been developed.
Structural characteristics of TCB Crystal seed Alloy
The advantage of anti-poisoning TCB crystal seed alloy is obvious, which can solve the poisoning problem of grain refinement, solve the problems such as hot cracking and shrinkage, solve the contradiction between grain refinement and improving electrical conductivity and thermal conductivity, and the application cost of TCB technology is low.
To sum up, TCB is not only a "super seed refiner", but also a new seed technology to enhance the added value of aluminum alloy products. It is a "golden key" and a powerful "grip" to open the research and development of new aluminum alloy materials and processing technologies.
three。 Application Technology of TCB Crystal seed
The innovative application of TCB crystal seed in the research and development of automotive aluminum alloy, ultra-high performance aluminum alloy and advanced aluminum alloy products is introduced, which highlights the unique advantages of crystal seed technology and has a broad application prospect.
Application of TCB in Al-Si Automotive Aluminum Alloy
Used in A356 aluminum alloy: anti-Si "poisoning", stable refinement effect, heat preservation 180min does not decline; compared with the traditional AlTiB master alloy, it can increase the strength and elongation of A356 Synchronize, especially the yield strength up to 274MPa, an increase of 19%.
Applied to the production of A356 aluminum wheels: adding 0.1% TCB, the refinement effect is much higher than 0.2% AlTiB, and there is no decline in the refinement effect, the shrinkage defects in thick and large parts are eliminated, and the elongation up to standard is greatly increased.
Applied to ZL114 aluminum alloy: its yield strength is 340MPa and its elongation is 10%, which is 38% and 75% higher than that of the original alloy, respectively.
Applied to high-performance engine aluminum pistons: for Gxxx multi-component Al-Si alloys, can TCBs containing 0.2% zirconium can resist Si/Zr "poisoning" at the same time? The application results show that there is no decline 6 hours after joining TCB, which proves that the application is feasible.
Applied to 7050 alloy: anti-Zr poisoning, achieve ultra-fine grains. At the same time, the fluidity is increased by 27.8%, and the hot crack is reduced by 66.7%. Adding 0.5%, the tensile strength is 725MPa, the yield strength is 660MPa, and the elongation is 10%.
When used in the production of 2xxx aluminum alloy: 0.4%TCB seed alloy can refine the grain size of 2024 aluminum alloy to 54.5 μ m, 0.2%TCB seed alloy can make the casting rod of 2A14 aluminum alloy with the same grain size as the gate and tail, and eliminate casting defects such as casting deficiency, shrinkage and hot cracking.
TCB seed technology can not only solve the problem of refinement "poisoning" caused by Si/Zr, but also solve the following problems:
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