Abstract
To realize the high-efficiency and high-performance manufacture of complex high-web panels, this paper introduced electric pulse current (EPC) into the stress relaxation aging forming process of 2219 aluminum alloy and systematically studied the effects of EPC, stress, and aging time upon the microstructure and properties of 2219 aluminum alloy. It is discovered that: (a) EPC greatly enhanced the mechanical properties after stress relaxation aging and reduced the sensitivity of the yield strength for the initial stress under the aging system of 165 °C/11 h; (b) compared with general aging, stress relaxation aging instead delayed the aging process of 2219 aluminum alloy and greatly increased the peak strength value; (c) EPC accelerated the aging precipitation behavior of 2219 aluminum alloy and reduced transgranular and grain-boundary energy difference, thus leading to a more diffused distribution of the transgranular precipitated phase and the absence of a significant precipitation-free zone (PFZ) and grain-boundary stable phase in the grain boundary, further improving the mechanical properties of the alloy.
Highlights
To manufacture the complex panels of a rocket fuel tank, some developed countries have conducted many studies on creep/stress relaxation aging forming technology, i.e., a manufacturing technique in which the stress relaxation forming and aging heat treatment strengthening are carried out at the same time by using the creep/stress relaxation property and aging precipitation strengthening property of aldural [1,2]
The initial stresses after the attaching-die of the components during the stress relaxation aging forming process are inconsistent, so the non-sensitivity of the mechanical properties to the initial stress after the stress relaxation is an essential condition of uniform component properties
The electric pulse current (EPC) generally improved the mechanical properties of the 2219 aluminum alloy after stress relaxation under the same aging system of 165 ̋ C/11 h, to 3.3%, 3.3% and 3.6%, respectively, on average
Summary
To manufacture the complex panels of a rocket fuel tank, some developed countries have conducted many studies on creep/stress relaxation aging forming technology, i.e., a manufacturing technique in which the stress relaxation forming and aging heat treatment strengthening are carried out at the same time by using the creep/stress relaxation property and aging precipitation strengthening property of aldural [1,2]. The technology boasts possessing advantages such as even deformation, high forming accuracy, good repeatability, excellent forming efficiency, low residual stress, stable dimensions and uniform properties, and can achieve the spatio-temporal integration of the manufacturing environment centered by formation and heat treatment strengthening. For this reason, it could realize the collaborative formation and heat treatment strengthening manufacture of complex high-web panels to some extent [3,4]. Some studies have demonstrated that different stress levels will inevitably cause different creep aging precipitation processes at points inside the component and non-uniform component properties. Many studies have confirmed that EPC can affect the phase
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