LM21 Aluminum vs China's Equivalent Aluminum Alloy ZL107

Comparison: LM21 Aluminum vs. China's Equivalent Aluminum Alloy (ZL107)

LM21 aluminum (British standard), a cast Al-Si-Cu alloy, is relatively close in performance and composition to China's cast aluminum alloy grade ZL107. Here is a detailed comparative analysis:

1. Composition Comparison

Element	LM21 (BS Standard)	ZL107 (GB/T 1173-2013)
Silicon (Si)	Approximately 6%	6.5%~7.5%
Copper (Cu)	Approximately 4%	3.5%~4.5%
Aluminum (Al)	Remainder (85.7%~91%)	Remainder
Other Elements	Trace amounts of Mn, Pb, etc.	Impurities (Fe, Zn, etc.) ≤ specified limits

2. Performance Comparison

Property	LM21	ZL107
Tensile Strength	About 190~220MPa in conventional casting	≥270MPa (sand casting, T6 treatment)
Yield Strength	8%~13% improvement with vibration casting	≥245MPa (sand casting, T6 treatment)
Elongation	~3%~5% with optimized vibration casting	≥2% (sand casting, T6 treatment)
Hardness (HB)	16% higher microhardness with vibration casting	≥100HB (sand casting, T6 treatment)
Casting Performance	Good, suitable for complex-shaped parts	Excellent fluidity and high air tightness

3. Similarities in Process and Application

Heat Treatment
Both can be strengthened via T6 heat treatment (solution treatment + artificial aging). LM21’s performance is optimized through vibration casting, while ZL107 achieves enhanced properties via conventional heat treatment and casting processes.
Application Fields

Automotive Industry: Used in engine blocks, cylinder heads, and pump bodies to reduce weight and improve wear resistance.
Mechanical Manufacturing: Suitable for gearboxes, valve bodies, etc., meeting requirements for strength and casting precision.
Differences: ZL107 is more widely used in domestic auto parts and agricultural machinery, while LM21 is common in European and American industrial sectors (e.g., secondary aerospace structural components).

4. Replacement Recommendations

For domestic procurement of materials similar to LM21, ZL107 is the first choice. Its composition and mechanical properties closely match LM21, with a mature domestic supply chain. Performance can be further optimized via heat treatment (e.g., T6) to meet most industrial needs.

If better weldability is required (LM21 has poor weldability due to high copper content), China’s ZL101A (Al-Si-Mg alloy) can be considered, though attention should be paid to differences in mechanical properties.

Summary

LM21 and China’s ZL107 aluminum alloys are highly similar in composition, performance, and application scenarios. ZL107 can be used as a domestic equivalent to LM21, with specific selection requiring further verification based on process requirements (e.g., casting method, heat treatment) and application scenarios.

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