The theory of stress corrosion for slow crack propagation is reviewed in the light of classical Griffith theory of fracture. Experimental data for stress corrosion cracking for glasses, ceramics, and metals are reviewed. We suggest that stress corrosion cracking plays an important role in the intrusion of magmas and in the transport of magmas upward through the lithosphere. It is shown that the effect of decreasing temperature (at progressively shallower levels along the geotherm) would be to decrease the crack velocity by several orders of magnitude if other factors were equal. We also propose that stress corrosion may be an important process in time-dependent earthquake phenomena such as premonitory behavior and earthquake aftershocks. We suggest that slow cracking in the earth is not seismically detectable but may nevertheless precede the terminal (catastrophic) phase of the fracture that is discerned as an earthquake. The seismically quiet periods before some earthquakes and the seismically quiet regions beneath some volcanoes may in fact be regimes of slow crack propagation. Slow crack propagation in a lithospheric plate may provide access routes for magmas which give rise to prominent linear volcanic chains.

Stress corrosion theory of crack propagation with applications to geophysics

Aluminium and its alloys Aluminium corrosion Atmospheric corrosion of aluminium Corrosion in water The action of mineral products The action of organic products The effect of different environments appendices

Corrosion of Aluminium

Stress corrosion cracking of aluminum alloys is reviewed. An extensive failure analysis shows how many service failures occurred in the aerospace industry over a ten year period and what kind of alloys and stresses led to initiation and propagation of stress corrosion cracks which caused these service failures. The paper contains most of the results of stress corrosion tests with aluminum alloys that have been obtained to date with fracture mechanics techniques. Stress corrosion crack growth rate measurements are compared with the results from smooth specimen testing and it is shown that the correlation between the different test results is very satisfactory. The present and limited status of theoretical understanding of stress corrosion cracking is outlined. A major part of the paper is devoted to the results of the latest alloy development. High strength aluminum alloys of dramatically increased stress corrosion resistance are available now. In the near future, stress corrosion resistant alloys of even higher strength might become available. What is still lacking is a detailed understanding of the mechanisms by which stress corrosion cracks initiate and propagate.

Stress corrosion cracking of aluminum alloys

This chapter focuses on two kinds of environmental fracture, stress corrosion cracking (SCC) and hydrogen embrittlement, and discusses the role in such failures of a number of metallurgical variables. These include chemical composition; microstructural components such as precipitate type and structure, and grain size and shape; crystallographic texture; heat treatment and its effect on the foregoing variables; and processing, particularly the thermomechanical treatments (TMT), which are attracting increased attention for property optimization. These variables are expected to be of great importance in the development of new engineering materials to meet demanding service conditions.

The Role of Metallurgical Variables in Hydrogen-Assisted Environmental Fracture

High-strength aluminum alloys are of considerable importance in our technologically advanced society Perhaps the best-known application is in the aerospace industry, where the high-strength aluminum alloys are the engineer’s mainstay for rockets, spacecraft, aircraft, and hydrospace vehicles Table 1 lists the chemical compositions for the commonly used high-strength aluminum-base alloys Composition limits for several of these alloys are shown in Fig 1 Typical applications for each of these alloys are listed in Table 2 The heat treatments for the various tempers of these alloys are given in Table 3 Mechanical properties of the alloys are listed in Table 4 (Data in Tables 1–4 were obtained from Refs 1–45a) The highest-strength aluminum alloys are those based on the Al-Cu-Mg (2000 series) and Al-Zn-Mg-Cu (7000 series) alloy systems Since these alloys are the most widely used for today’s high-performance structures, this chapter will concentrate on them

Stress-Corrosion Cracking of High-Strength Aluminum Alloys

AN UP TO DATE REVIEW OF THE STRESS CORROSION CRACKING PERFORMANCE OF WROUGHT HIGH STRENGTH ALUMINUM ALLOYS IS PRESENTED. SPECIAL EMPHASIS IS PLACED ON FACTORS OF MICROSTRUCTURE AND ITS DIRECTIONALITY AND THE EFFECT OF ANCILLARY ALLOYING ELEMENTS AND ENVIRONMENTAL FACTORS. EXAMPLES OF TYPICAL SERVICE PROBLEMS ENCOUNTERED WITH STRESS CORROSION CRACKING OF HIGH STRENGTH ALUMINUM ALLOYS ARE DESCRIBED ALONG WITH MEANS OF COMBATING THEM, SUCH AS PEENING, COATINGS, OR THE USE OF SPECIAL STRESS CORROSION RESISTANT ALLOYS.

MB Shumaker

Papers

The Resistance of Wrought High Strength Aluminum Alloys to Stress Corrosion Cracking