Availability of Al-Mg alloys for use as electrical contact resistors

Fretting experiments associated with contact resistance were carried out with Al-Mg alloys (Al-3wt%Mg and Mg-3wt%Al). It was found that the contact behavior of these alloys is considerably different; the saturation value is 2.5 m/spl Omega/ at a load less than 1N for A-3wt%Mg irrespective of humidity and has almost the same value (3 m/spl Omega/) at 2N with a relative humidity under 30%RH for Mg-3wt%Al. The number of cycles at the saturation value of the contact resistance in Mg-Al decreases with increasing humidity. The analysis of the fretted surface with electric current showed that the X-ray diffraction intensity of MgO formed during fretting in Mg-Al increases monotonously with the increase of the relative humidity, but in samples without electric current there is a transition giving a maximum at about 50%RH. These results make it clear that the wear behavior is subject to the electrical contact condition in each alloy. On the basis of the experimental results, the effects of Mg (or Al) as an Al (or Mg) additive on the electrical contact property are discussed.