Thermal Stability of Aluminum Alloys

Abstract

Thermal stability, determining the material ability of retaining its properties at required temperatures over extended service time, is becoming the next frontier for aluminum alloys. Its improvement would substantially expand their range of structural applications, especially in automotive and aerospace industries. This report explains the fundamentals of thermal stability; definitions, the properties involved; and the deterioration indicators during thermal/thermomechanical exposures, including an impact of accidental fire, and testing techniques. For individual classes of alloys, efforts aimed at identifying factors stabilizing their microstructure at service temperatures are described. Particular attention is paid to attempts of increasing the current upper service limit of high-temperature grades. In addition to alloying aluminum with a variety of elements to create the thermally stable microstructure, in particular, transition and rare-earth metals, parallel efforts are explored through applying novel routes of alloy processing, such as rapid solidification, powder metallurgy and additive manufacturing, engineering alloys in a liquid state prior to casting, and post-casting treatments. The goal is to overcome the present barriers and to develop novel aluminum alloys with superior properties that are stable across the temperature and time space, required by modern designs.

Optimizing Heat Treatment Parameters for the W-Temper Forming of 7xxx Series Aluminum Alloys

“…However, this effect should not be very pronounced after the relatively long ageing times used here. On the other hand, precipitate coarsening under service conditions can strongly deteriorate the strength [29]. As discussed above, there is an indication that the precipitates are coarser if a forming operation is involved.…”

Analysis of Metal Systems for Developing Creep-Resistant Aluminum Alloys. A Review.

“…It is able to reduce the harmful effects of iron in Al-Cu, Al-Si-Cu, Al-Mg, and Al-Mg-Si, as well as increase their corrosion resistance and strength. Manganese, like copper, increases the heat resistance of aluminum alloys and reduces the coefficient of linear thermal expansion of aluminum alloys, which in its turn increases the crack resistance of castings made of them [1,6,15,16].…”

“…at 640 0 C and 527 0 C, respectively [3,10,35]. For this system, it is possible to implement the mechanisms of dispersing the strengthening of the aluminum matrix by thermally stable and diffusion-inactive particles of Al 3 Ni intermetallic [2], similar to the Al-Fe system and some others [3,16].…”

Microstructure and Mechanical Properties of Aluminum Cast Alloy A356 reinforced with Dual-Size B4C Particles

“…luminum alloys find application in diverse fields owing to their high strength-to-weight ratio, low cost, and ease of fabrication [1][2][3]. Substituting the base aluminum alloys with particulate composites has the advantage of improving the mechanical strength parameters without seriously disturbing the thermal and electrical conductivities and other properties A [4][5][6][7]. The common reinforcement particles used in AMMCs are graphite, SiO 2 , SiC, Al 2 O 3 and B 4 C used in small percentages of about 2 to 8% [8][9][10][11][12].…”