How to Choose the Best Aluminum Alloy? Ming Ming Aluminium Explains the Properties and Applications of Gravity Casting Materials

When launching a new manufacturing project, many product designers and engineers often ask a key question:
“Which aluminum alloy is best for gravity casting?”
It’s a very good question — but the answer is not singular. In fact, there’s no absolute “best”, only the “most suitable”. The key lies in understanding the final application scenario and performance requirements of the product.

As a specialist in aluminum alloy gravity casting with deep roots in Taiwan, Ming Ming Aluminium Co., Ltd. frequently assists clients in material evaluation. Selecting the correct alloy grade is the first step to determining the casting’s strength, lifespan, corrosion resistance, and cost-effectiveness. Today, we’ll guide you through some of the most common aluminum alloys used in gravity casting, and how to make wise choices based on their characteristics.

Among the many aluminum alloy series, Aluminum-Silicon (Al-Si) alloys are without doubt the stars of the gravity casting field. Their popularity mainly stems from their outstanding castability. The addition of silicon significantly improves molten aluminum’s fluidity, allowing it to easily fill every corner of the mold while reducing solidification shrinkage. This minimizes casting defects and produces dense, high-quality structures.
※ While Al-Si alloys have excellent castability, under certain gravity casting conditions they still have a minimum wall thickness limit (Min. 4.5 mm).
Within this family, different grades are created by adding trace elements to meet diverse performance demands.
※ Includes Al-Si alloy grade and composition tables vs. international standards A356 / A357 / ZL104 / A380 / ADC12 / AC4B.

• A356 / A357 — The First Choice for High-Performance Gravity Casting
  In the realm of aluminum gravity casting, A356 (Al-Si-Mg) has earned its reputation thanks to its exceptional all-round properties. It offers superior castability and corrosion resistance, with its most notable advantage being its excellent responsiveness to T6 heat treatment. After T5 or T6 treatment, the tensile strength, yield strength, and hardness of A356 increase significantly, delivering outstanding mechanical performance. Additionally, A356 can withstand multiple repeated heat treatments.
  A357 is essentially an upgraded variant of A356, with higher purity and even more impressive mechanical properties.
  When your parts need to withstand high stress, intense vibration, or heavy impact — and demand stringent strength, toughness, and long-term reliability — A356/A357 is your ideal solution. Applications range widely, from automotive suspension components and high-performance wheels to EV motor housings, robotic structural parts, and high-pressure valve bodies.
  
  

• ZL104 — Strength and Dimensional Stability in One Package
  ZL104 is another high-performing Al-Si-Mg-Mn alloy. Even in its as-cast state, it delivers strong all-round mechanical properties and airtightness, and it can be further enhanced through heat treatment.
  Its standout feature is dimensional stability — it resists deformation caused by temperature fluctuations, maintaining tight tolerances over time.
  
  This makes ZL104 particularly suitable for parts operating under moderate loads but requiring strict airtightness and dimensional accuracy, such as hydraulic pump housings, pneumatic tool parts, engine intake manifolds, or precision instrument casings demanding high sealing performance.
  
  
• ADC12 / A380 — The Cost-Performance Balancers
  ADC12 and A380 are ideal choices where cost-effectiveness is the priority. Although more common in die casting, these Al-Si-Cu alloys, with their exceptional fluidity and mold-filling ability, also hold a place in gravity casting, capably handling complex shapes.
  
  Their biggest advantage is economical cost. However, because they contain copper, their corrosion resistance is slightly lower than A356, and their elongation is reduced (they are more brittle). As such, they are suited for parts where extreme strength is not required and heat treatment is unnecessary — but where excellent castability and budget control are more important. Typical uses include brackets, housings, and heat sinks for various equipment in non-critical load applications.

From high-strength A356 to cost-effective ADC12, every aluminum alloy has its own unique value. The best choice always starts with a clear definition of product requirements.
At Ming Ming Aluminium Co., Ltd., we don’t just provide casting services — we offer professional material selection consultation. Our team works with you to analyze load conditions, operating environment, post-processing needs, and budget constraints, recommending the optimal alloy from the outset to ensure your product is born with the strongest foundation.