Alloy plate: a performance revolution of multi-material fusion

Alloy plates, as the most "creative" branch of the metal material family, break the performance limitations of a single metal by fusing and rolling different elements in precise proportions, and become the core material of "customization on demand" in modern industry. From ultra-thin precision plates of a few millimeters to heavy structural plates of tens of centimeters, from normal temperature environments to extreme working conditions, alloy plates support technological breakthroughs in aerospace, energy, construction and other fields with their adjustable strength, corrosion resistance, and lightweight properties.
1. The core logic of alloying: "precise formula" of performance
The charm of alloy plates comes from the alloying magic of "1+1>2". By adjusting the ratio of base metal and alloying elements, engineers can accurately control the performance of plates like mixing medicines to meet the diverse industrial needs.

The balance between strength and toughness is the core research and development direction of alloy plates. In alloy plates based on steel, adding manganese (Mn) can improve strength (tensile strength increases by about 40MPa for every 1% increase in Mn), but excessive addition can lead to brittleness; adding microalloying elements such as vanadium (V) and niobium (Nb) can increase strength by more than 30% by refining grains while maintaining good toughness - this "high-strength low-alloy (HSLA) steel plate" has become the preferred material for automobile weight reduction and bridge construction, with a yield strength of 355-690MPa and an elongation of more than 20%.

In the field of lightweighting, the alloying logic of aluminum alloy plates is more sophisticated. The strength of pure aluminum is only about 90MPa, which cannot meet the structural requirements. However, after adding copper (Cu), magnesium (Mg), and silicon (Si), through the "aging strengthening" mechanism, the strength of the 6-series aluminum alloy plate (Al-Mg-Si) can reach 300MPa, but the density is only 1/3 of that of steel, making it an ideal material for high-speed rail bodies and drone racks; the higher-end 7-series aluminum alloy (Al-Zn-Mg-Cu) has a strength of over 600MPa after heat treatment, combining lightweight and fatigue resistance, and is a key material for the wing skin of large passenger aircraft.

The adaptability to extreme environments relies on the "synergistic protection" of alloy elements. In the field of corrosion resistance, stainless steel plates (iron-chromium-nickel alloy) form a passivation film through chromium elements, and nickel elements stabilize the austenite structure. 316 stainless steel has a salt spray resistance of more than 3 times that of 304 due to the addition of 2%-3% molybdenum (Mo), becoming the "anti-corrosion shield" for marine engineering and chemical equipment; in the high temperature field, nickel-based alloy plates (such as Inconel 625) can maintain strength in an oxidizing environment above 1000°C by adding chromium, molybdenum, and niobium, and are used for gas turbine blades and nuclear reactor shells.
2. Mainstream alloy plate types: precise matching of characteristics and scenarios
The classification of alloy plates is not simply divided by base metal, but rather forms multiple application branches based on performance, and each type of plate has its irreplaceable core advantages.
1. Structural alloy plate: the "skeleton" of the load-bearing industry
High-strength low-alloy steel plate (HSLA): low-carbon steel is used as the matrix, with micro-alloy elements such as niobium, vanadium, and titanium added, with a yield strength of 295-690MPa, and good weldability and formability. It is widely used in bridge girders (such as the steel box girders of the Hong Kong-Zhuhai-Macao Bridge) and large container ship hulls, reducing weight by 30% while improving structural safety.
Aluminum alloy structural plates (2 series, 7 series): 2 series aluminum alloy (Al-Cu-Mg) has a strength of 450MPa and is suitable for making aircraft fuselage frames; 7 series aluminum alloy (Al-Zn-Mg-Cu) has a strength of over 600MPa and is the core material of the spacecraft body structure. Through heat treatment, it can achieve dual optimization of "strength and toughness".
Titanium alloy plate (TC4): The density of titanium-aluminum-vanadium alloy is only 4.5g/cm³ (about 1/2 of steel), but its strength is comparable to that of high-strength steel, and its performance is stable in the range of -253℃ to 600℃. It is the preferred material for deep-sea detector pressure hulls and rocket fuel tanks, and can withstand the huge pressure of 7,000 meters deep sea.
2. Functional alloy plate: giving materials "special skills"
Corrosion-resistant alloy plate: In addition to stainless steel, Hastelloy C-276 contains 16% chromium, 16% molybdenum, and 4% tungsten, and is highly resistant to strong corrosive media such as sulfuric acid and hydrochloric acid, and is used for chemical reactor linings; copper-nickel alloy plates (B10, B30) have a corrosion rate of only 0.02mm/year in seawater, and are standard for ship condensers and seawater desalination equipment.
Heat-resistant alloy plate: Nickel-based superalloy plate (such as GH4169) still maintains a tensile strength of 700MPa at 650℃, and the oxidation rate is only 0.01mm/1000 hours. It is used for high-temperature resistant parts of aircraft engine combustion chambers and industrial furnaces; cobalt-based alloy plate (Stellite 6) still has excellent wear resistance above 800℃, suitable for making high-temperature bearings.
Electrically conductive and thermally conductive alloy plate: Copper alloy plate (such as beryllium bronze, tungsten copper alloy) has both high strength and high conductivity. The conductivity of beryllium bronze plate reaches 20% IACS and the strength is 1200MPa. It is used for conductive contacts of high-voltage switches; aluminum-copper composite plate becomes an efficient material for power battery tabs through the combination of "lightweight aluminum + high conductivity of copper".
3. Composite alloy plate: "material puzzle" with complementary performance
Explosive composite plate: Through the high pressure generated by the explosion of explosives, dissimilar metal plates (such as titanium-steel, copper-aluminum) are welded in milliseconds, and the bonding strength reaches more than 200MPa. Titanium-steel composite plates retain the corrosion resistance of titanium and use the strength of steel to reduce costs. They are widely used in chemical storage tanks; copper-aluminum composite plates solve the problem of dissimilar metal welding and become an ideal choice for power busbars.
Coated alloy plate: The corrosion resistance of zinc-aluminum-magnesium alloy coated steel plate (ZM coated) is 5-10 times that of ordinary galvanized plate, and the salt spray test can reach more than 3,000 hours. It is used for highway guardrails and container roofs, greatly extending the service life.
3. Manufacturing process: precision control from smelting to rolling
The performance of alloy plates depends not only on the composition design, but also on the extreme control of the manufacturing process. From molten steel to finished plate, each process reshapes the microstructure of the material and ultimately gives it stable performance.

The melting process is the starting point of the "genetic coding" of the alloy plate. In the electric arc furnace or vacuum induction furnace, the base metal and the alloying elements need to be fused under precise temperature control (error ±5℃) to ensure the uniformity of the composition - for example, the chromium distribution deviation of the stainless steel plate needs to be controlled within 0.5%, otherwise there will be local corrosion-resistant weak areas. For high-purity alloys (such as aviation titanium alloys), a vacuum consumable arc furnace is required for three smeltings to reduce the oxygen content to below 0.015% to avoid the formation of brittle phases.

The rolling process determines the morphology and mechanical properties of the alloy plate. The hot rolling process is carried out above the recrystallization temperature (800℃+ for steel and 300℃+ for aluminum). Through multiple rolling passes, the thickness of the billet is reduced by more than 90%, and the grains are refined at the same time - the hot rolling of high-strength steel plates needs to control the final rolling temperature at 850-900℃ to ensure uniform austenite grains and lay the foundation for subsequent heat treatment. The cold rolling process is carried out at room temperature. Through multi-roll rolling of the cold rolling mill (such as a 20-roll rolling mill), the thickness of the plate is controlled at 0.01-3mm, and the surface roughness reaches Ra0.1μm, which is suitable for precision parts (such as aluminum alloy plates for mobile phone middle frames).

Heat treatment is the key to "activating" performance. "Solid solution + aging" treatment of aluminum alloy plates: heat the plate to 500℃ to fully dissolve the alloy elements, quickly water cool it and keep it at 120℃ to precipitate a uniform strengthening phase, which increases the strength by 2-3 times; while the "quenching + tempering" of martensitic stainless steel plates is achieved by high-temperature heating and oil cooling, obtaining high hardness (above 50HRC), and then low-temperature tempering to eliminate internal stress, taking into account wear resistance and toughness.

IV. Application scenarios: full coverage from macroscopic structure to microscopic precision
The application map of alloy plates spans from "ton level" to "gram level", showing customized performance advantages in different scenarios.

In large-scale projects and infrastructure, alloy plates are "load-bearing". The navigation bridge of the Hong Kong-Zhuhai-Macao Bridge uses 16mm thick Q690D high-strength alloy steel plates, which can withstand a pressure of 690MPa per square meter, 40% lighter than ordinary steel plates, and have low-temperature impact toughness of -40℃; the roof steel structure of Beijing Daxing International Airport uses 3mm thick weather-resistant alloy steel plates (Corton steel), which are self-protected by forming a dense rust layer on the surface, eliminating the need for painting and maintenance, and have a service life of more than 100 years.

The aerospace field places extreme demands on alloy plates. The Boeing 787 fuselage uses a 2.5mm thick aluminum-lithium alloy plate, which is 10% lighter than traditional aluminum alloy and increases the aircraft's range by 300 nautical miles; the rocket engine nozzle extension uses a 0.3mm thick nickel-based alloy plate (Inconel 718), which remains stable under the alternating effects of -253℃ liquid oxygen and 1000℃ gas, and needs to withstand 1000 times/second thermal shock per square centimeter.

The precision manufacturing and consumer fields reflect the "delicate side" of alloy plates. The middle frame of the smartphone uses a 0.8mm thick 7000 series aluminum alloy plate, and the flatness error after CNC processing is ≤0.01mm, taking into account both lightweight and drop resistance; the battery shell of the new energy vehicle uses a 1.5mm thick 5 series aluminum alloy plate, which is sealed by laser welding, with a protection level of IP67, and has excellent thermal conductivity (thermal conductivity coefficient 150W/(m・K)), ensuring uniform heat dissipation of the battery.
V. Future Trends: Double Breakthroughs in Greening and Functionalization
With industrial upgrading and environmental protection needs, alloy plates are evolving in the direction of "lighter, stronger, and smarter", and the integration of material innovation and manufacturing technology has spawned new possibilities.

High performance and lightweight in parallel. The density of the third-generation aluminum-lithium alloy plate has dropped to 2.6g/cm³, and the strength has exceeded 700MPa, which will further reduce the weight of the aircraft; and the "nano-composite alloy plate" has achieved a breakthrough in the laboratory stage by introducing nano-level strengthening phases (such as carbon nanotubes and graphene) into the matrix, which increases the strength by 50% while maintaining toughness.

Functional composites expand the application boundaries. "Photovoltaic + alloy plate" architectural integration: composite photovoltaic film on the surface of aluminum alloy plate, which serves as the exterior wall of the building and generates electricity, with a conversion efficiency of more than 20%; "self-healing alloy plate" adds shape memory alloy particles, and can automatically restore to its original state after being deformed by force and heated to a specific temperature, which is expected to be used for structural repair of spacecraft.

Green manufacturing and circular economy have become industry consensus. Short-process smelting (using scrap alloy as raw material) reduces carbon emissions by 60%. At present, the recycling rate of aluminum alloy plates in Europe has reached 70%; and the "near net shape" rolling technology increases the material utilization rate from 70% to 95% by precisely controlling the thickness tolerance (±0.001mm), reducing waste generation.

The development history of alloy plates is the history of human exploration of continuous breakthroughs in material properties - from the limitations of a single metal, to the fusion of multiple alloys, to the innovation of functional composites, each step promotes the progress of industrial civilization. In the future, with the development of the material genome plan and intelligent manufacturing technology, alloy plates will achieve "on-demand design and precise manufacturing", and write new possibilities in more unknown fields.