Effects of Cryogenic Treatment on the Microstructure and Residual Stress of 7075 Aluminum Alloy

Abstract

The effect of cryogenic treatment (CT) on the microstructure, residual stress, and dimensional stability of 7075 aluminum alloy under temperatures of 0 • C, −60 • C, −120 • C, and −196 • C were studied, using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), an X-ray diffractometer, and an X-ray stress tester. The results indicated that CT can facilitate the dissolution of the coarse secondary phase into the α(Al) matrix, promote uniform distribution of Mg, Cu, Zn elements, and increase the density of fine secondary phases in the 7075 Al alloy. The CT can also induce the rotation of the α(Al) grain towards (200), through the processes of recovery and recrystallization. It was found that the residual stress was released, and a higher dimensional stability of the 7075 aluminum alloy was achieved, after CT. Experimental results demonstrated that the optimum CT temperature for the 7075 aluminum alloy is −120 • C.

Complex Interdependency of Microstructure, Mechanical Properties, Fatigue Resistance, and Residual Stress of Austenitic Stainless Steels AISI 304L

“…Such behavior follows the cryogenic contraction theory [ 9 , 10 ] and the reduction in the tensile state of the material with DCT as determined for other metallic materials and alloys well [ 10 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. This tremendous change (200 MPa reduction) in the stress state for the first group is a possible reason for the increased hardness with DCT, as it relates directly to the more rigid response of the material to external compressive stresses that are performed during hardness measurement.…”

Revealing the Pb Whisker Growth Mechanism from Al-Alloy Surface and Morphological Dependency on Material Stress and Growth Environment

“…This process allows the application of uniform shrinkage pressure onto the material, which in turn modifies the internal stress state of the material. As shown by different investigations, DCT reduces tensile residual stresses or even changes them into a compressive type [ 41 , 42 , 43 , 44 ]. For the whisker preparation, all samples were cut, ground down to 4000 grit paper and polished with 3 μm and 1 μm diamond suspension.…”

Effect of cryogenic treatment on properties of materials: A review

“…Different material characterization techniques have been used by researchers to characterize material after cryogenic treatment, such as optical microscope, 50,130,148,149 Scaning Electron Microscopy (SEM), 116,135,136,147 Secondary Electron Detector (SED), 2,4,14,15 Back Scattered Electron Detector (BSED) 15,24,72,150 and Energy Dispersive Spectroscopy (EDS). 73,143,151,152 Optical microscope is used as a primary device to get the brief idea about the material before using some more sophisticated devices. 153 SED is for topographical details while BSED provides both topographical and composition details but exact detection of composition is not possible with BSED.…”