Aluminium work-hardenable

Commercially pure aluminium (1000 series) and the non-heat-treatable aluminium alloys (3000 and 5000 series) are usually work hardened. The work hardening superimposes on any solution hardening, to give considerable extra strength (Table 10.5). 

Table 10.5 Yield strengths of work-hardened aluminium alloys...

Two pieces of work-hardened 5000 series aluminium alloy plate were butt welded together by arc welding. After the weld had cooled to room temperature, a series of hardness measurements was made on the surface of the fabrication. Sketch the variation in hardness as the position of the hardness indenter passes across the weld from one plate to the other. Account for the form of the hardness profile, and indicate its practical consequences. 

Aluminium is very malleable and ductile and easily formed into containers. During the process it is subject to work hardening which can be used to advantage in producing rigid containers. Alternatively the formed containers can be annealed to restore the softness and flexibility, e.g. in producing collapsible aluminium tubes. 

The impact extrusion process is used to produce open-ended collapsible tubes from softer metals such as tin and lead. When aluminium is used, it work-hardens during the forming process and the resultant tubes must be annealed to regain flexibility. Alternatively aluminium tubes may be left in their work-hardened state as rigid containers. Impact extrusion is a particularly useful process to produce containers with a high length to diameter ratio, e.g. up to 7 1. A slug of the metal to be formed is held in a female die and is struck by a punch which has the same form as that of the inside of the ultimate container. Upon impact the metal flows up the outside of the punch. A stripper plate then removes the extruded container on its return stroke. 

The conductors are usually copper or aluminium. Aluminium is seldom used in the oil industry because it work hardens during installation, has higher losses, has high volt-drop at rated current and requires special attention during termination. 

The ultimate tensile strength of pure aluminium increases markedly with increasing amounts of alloying or impurity additions, as shown in Fig. 3.1-10. Unalloyed aluminium is soft (tensile strength 10—30 MPa, Table 3.1-11) and, like all fee metals, shows a low rate of work hardening. 

Structure and Basic Mechanical Properties of Wrought Work-Hardenable Aluminium Alloys... 

Whiskers (Cont.) hardness (Cont.) of MgO, 265 of SiC, 261 Work of adhesion, 28 Work of elastic recovery of indent, 48 Work hardening, 45-46, 103, 106 of aluminium, 46, 262 and anisotropy peaks. 111, 115-116 caused by soft slider, 266 of crystals, 72 depth of, 45-46, 267 and diverging slip systems, 116 equation for, 266 of magnesia, 46, 265-267 and plastic zone anisotropy, 111 of SiC, 111... 

These two-pack cold-cure solvent-borne coatings have excellent durability and abrasion resistance. They are designed for spray applications on steel, aluminium and light alloy surfaces wMch have been suitably pretreated. Base and hardener are mixed in 3 1 or 5 1 ratios as recommended by the manufacturer and the pot life is around 2 hours under normal working conditions (20 C) and should not be used after the stated time. Polyurethane/acrylic resin combination is also available. Two-pack polyurethanes are widely used in veMcle body repair and can contain isocyanate which is a basic constituent in the production of polyurethane and is the most common cause of industrial asthma and it is also a skin irritant. It should be easily identified by a label on the container which should say contains isocyanates, harmful by inhalation and in contact with skin . Waterborne two-pack polyurethane finishes are available. 

More work is being done on metallic fillers to investigate the filler/matrix adhesion, as other workers have found that additions of copper, zinc and aluminium produce quite varied results when tested in tension. Indeed the authors have also found that zinc will react readily with dicyandiamide, which is commonly used as a hardener in epoxies. The reaction can cause severe foaming and a change in the structure of the cured epoxy at the interface with the zinc. 

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