Thermal expansion of aluminum and various important aluminum alloys

Abstract

This paper gives data on the linear thermal expansion of 4 samples of aluminum and 51 samples of important aluminum alloys. The preparation, chemical composition , heat treatment, etc., are included. Most of the specimens were examined from room temperature to about 500 C. Typical expansion curves of the various groups of samples are shown and discussed. A description of the apparatus used in this research and a review of available information obtained by previous observers on the thermal expansion of aluminum and some of its alloys, are given. The expansion of cast aluminum (99.95 per cent) from room temperature to 6io° C. is represented by the following equation : L=L [i+(22. 5 S /+0.00989 f) 10-6] The relations between the chemical compositions and coefficients of expansion of aluminum-copper alloys (4 to 12 per cent copper) and aluminum-silicon alloys (4 to 12.5 per cent silicon), are shown in figures. The anomalous expansion of two aluminum zinc alloys at constant temperature (about 270 C. on heating) is shown. From the results of previous observers and the present research, it is evident that the aluminum zinc alloy of eutectoid composition (about 79 per cent zinc) shows the greatest change in expansion at the transformation or eutectoid temperature. A triangular diagram is shown which indicates the effect of change of composition on the coefficients of expansion of aluminum-silicon-copper alloys lying near the aluminum corner of the ternary system. The table in the summary gives a comparison of the average coefficients of expansion of the various groups of samples investigated. CONTENTS Page I. Introduction 698 II. Previous determinations 698 III. Materials investigated 704 IV. Apparatus 704 V. Results 705 1. Aluminum (series 1) 705 (a) Pure aluminum 705 (b) Commercial aluminum 707 2. Aluminum-copper alloys (series 2) 709 3. Aluminum-silicon alloys (series 3) 712 4. Aluminum-zinc alloys (series 4) 717 5. Aluminum-manganese and aluminum-manganese-copper alloys (series 5) 723 6. Aluminum-silicon-copper and aluminum-silicon-copper-manganese alloys (series 6) 723 7. Duralumin (series 7) 726 8. " Verilite" (series 8) 728 VI. Summary 729 697 698