Tensile, Fatigue, and Creep Properties of Aluminum Heat Exchanger Tube Alloys for Temperatures from 293 K to 573 K (20 °C to 300 °C)

Abstract

Since automotive heat exchangers are operated at varying temperatures and under varying pressures, both static and dynamic mechanical properties should be known at different temperatures. Tubes are the most critical part of the most heat exchangers made from aluminum brazing sheet. We present tensile test, stress amplitude-fatigue life, and creep-rupture data of six AA3XXX series tube alloys after simulated brazing for temperatures ranging from 293 K to 573 K (20°C to 300°C). While correlations between several mechanical properties are strong, ranking of alloys according to one property cannot be safely deduced from the known ranking according to another property. The relative reduction in creep strength with increasing temperature is very similar for all six alloys, but the general trends are also strong with respect to tensile and fatigue properties; an exception is one alloy that exhibits strong Mg-Si precipitation activity during fatigue testing at elevated temperatures. Interrupted fatigue tests indicated that the crack growth time is negligible compared to the crack initiation time. Fatigue lifetimes are reduced by creep processes for temperatures above approximately 423 K (150°C). When mechanical properties were measured at several temperatures, interpolation to other temperatures within the same temperature range was possible in most cases, using simple and wellestablished equations.

Evolution of Elevated-Temperature Strength and Creep Resistance during Multi-Step Heat Treatments in Al-Mn-Mg Alloy

“…On the other hand, the solid-solution strengthening from Mn atoms is reported to have a linear relationship with solute Mn concentration, as [ 36 ]: where H and α are constant, i.e., 18.35 and 0.9 for solute Mn atom under at RT , or 10 and 0.8 at 300 °C under the conditions applied in the present work (strain rate at 10 −3 s −1 and total strain at 0.2%) [ 1 , 36 , 37 , 38 ]. C is the concentration of solute Mn atom in Al matrix, and can be estimated using EC by neglecting the contribution of Fe and Si on EC due to their low solubility with the following equation [ 27 ]: …”

Improving Elevated-Temperature Strength of an Al–Mn–Si Alloy by Strain-Induced Precipitation

“…The effect of solutes on electrical resistivity can be evaluated by a linear relationship as [3]: ρ = 0.0267 + 0.032Fe% + 0.033Mn% + 0.0068Si% (1) Fe%, Mn%, and Si% are the solute concentrations in wt. %.…”

“…The current development of the aerospace and automotive industries demands cost-effective lightweight materials with high elevated-temperature strength [1,2]. Aluminum alloys are candidate structural materials for lightweight applications.…”

Analysis of the Microstructure and Selected Properties of the Aluminium Alloys Used in Automotive Air-Conditioning Systems

“…Consequently, various steps are taken to make the walls of components as thin as possible, while maintaining or even increasing the working pressure and operating temperature. Meeting such requirements is not an easy task, as it means there is a need to keep different properties that often exclude each other at an equally high level [1][2][3]. Modern automotive heat exchangers operate at a temperature of about 100 • C and a pressure of up to 250 kPa (2.5 bars), but in heavy vehicles, the heat exchanger temperature can even reach 275 • C at a pressure of up to 350 kPa (3.5 bars) [1].…”