7075 Aluminum Rod

The core heat treatment of 7075 aluminum bars involves three steps: solution treatment, quenching, and aging. The mainstream states are T6 (highest strength), T73 (best corrosion resistance), and T651 (stress-relieved). The first step is solution treatment, with the temperature controlled at 460-480℃ (475℃ is commonly used in the industry). The solution is held for 1-2 hours per 25 mm thickness to allow the alloying elements to fully integrate into the matrix. After solution treatment, it must be rapidly quenched in flowing cold water at 20-40℃ within 5 seconds to stabilize the internal microstructure.

Main Conditions (T Series) Process Parameters

1. T6 Condition (Most Commonly Used, Highest Strength)

Solution Treatment: 470-480℃, Holding for 1-2 hours

Quenching: Rapid water cooling (≤5 seconds transfer)

Artificial Aging: 120-130℃, Holding for 24-36 hours

Properties: Tensile strength approx. 572MPa, Yield strength approx. 503MPa, Hardness approx. 150HB

2. T73 Condition (High Corrosion Resistance, Sacrificing Some Strength)

Solution Treatment: Same as T6, 470-480℃, Holding for 1-2 hours

Quenching: Same as T6, Rapid water cooling

Double-Stage Aging:

First Stage: 105-115℃, Holding for 6-8 hours

Second Stage: 160-170℃, Holding for 8-10 hours

Advantages: Significantly improved resistance to stress corrosion cracking (SCC), suitable for corrosive environments such as marine and chemical plants.

3. T651 Condition (T6 with added tensile stress release)

Solution + Quenching: Same as T6

Tensioning: 1-3% cold stretching after quenching to eliminate residual quenching stress

Artificial Aging: Same as T6, 120-130℃, holding for 24-36 hours

Advantages: Less machining deformation, suitable for precision machining and large structural parts

Key Process Points

Solution Temperature Control: Below 460℃, elements do not dissolve sufficiently; above 480℃, overheating is likely, damaging performance.

Quenching Transfer Time: ≤5 seconds, to avoid premature precipitation of strengthening phases leading to a decrease in strength.

Aging Temperature Accuracy: ±2℃, to ensure uniform and fine precipitates, affecting the final strength and toughness balance.

Aluminum Rod Manufacturer's Recommendation: Condition Selection Principles: Choose T6 for high strength; choose T73 for corrosion resistance; choose T651 for precision machining. 7075 is a heat-treatable strengthening alloy; its strength in the non-heat-treatable state (O state) is only about 1/3 of that of T6.