Studies on the Work-Hardening Behavior of AA2219 under Different Aging Treatments

Abstract

Uniaxial tensile tests were performed to examine the influence of the precipitation state on the yield strength and work-hardening behavior of AA2219 for different aging treatments. The microstructural observations in four aging treatments (viz. natural aging, underaging, peak aging, and overaging) were made through transmission electron microscopy (TEM) to understand the type of phase or intermediate stages of the phase present (Guinier-Preston (GP) zones, h¢¢, h¢, and h). To characterize the work-hardening behavior, the analysis of the experimental results has focused on two parameters, viz. the initial work-hardening rate H max ("dr/de) and the slope (dH/dr) of the H-r plot, which is related to the rate of dynamic recovery. The initial work-hardening rate (H max ) first drops as aging proceeds and then increases significantly upon overaging. The large increase in H max is also associated with a concomitant increase in the slope (dH/dr) of the H-r curve. The material constants in the differential equation for the dislocation density are evaluated and flow stress vs plastic strain curves are generated using the flow stress contributions from the solid-solution, dislocation, and precipitation hardening. The model predictions are found to be in excellent agreement with the experimental data for a range of precipitation states from underaged (UA) to overaged (OA) conditions. Curves of flow stress due to dislocation hardening with the plastic strain were also generated in the presence of shearable and nonshearable precipitates.

Effect of friction stir processing on the tensile and fatigue behavior of a cast A206 alloy

“…Similar hardening behavior was also observed in other age-hardenable wrought Al alloys; e.g., see Ref. [31][32][33]. Naturally aged Al alloys containing very fine coherent precipitates show a prolonged (in terms of stress) work-hardening region.…”

Study on strength and fracture toughness of Al-Zn-Mg-Cu-Ti(-Sn) alloys

“…Primary voids are inclined to nucleation on particles interior or particle/matrix interface decohesion. Second phase particles with smaller sizes favors micro voids nucleation [41], The Mg2Sn particles can be observed to distribute in the fine dimples ( Fig. 9) and was not broken, different from coarse constituent particles which provide a major path for fatigue crack propagation, suggesting that Mg2Sn may initiate the microvoids and facilitate the dimple formation, thus increase the tendency of dimple-type transgranular fracture and is consistent with toughness improvement.…”

Development and Characterization of Cast Modified SI-CU-MG Alloys for Heat Resistant Power Train Applications

“…On the other hand, coarse particles are non-shearable and form Orowan loops by bowing the dislocation line. Thus, the presence of precipitates adds to the microstructure complexity and affects mechanical properties of alloys [55,146,147].…”