May 18, 1900.] 



SCIENCE. 



783 



ALU3IINIUM-3IAGNESIUM ALLOYS. 

 There have recently appeared accounts 

 of a ' newly discovered ' series of alloys of 

 aluminium and magnesium which are con- 

 sidered by their discoverers peculiarly val- 



variation of quality and the law of such 

 variation is from a paper i-ead by Professor 

 Carpenter, in 1898, before the American 

 Society of Mechanical Engineers and pub- 

 lished in their transactions for that year. 



Tenacity of Magnesium. 



Alloys of Aluminium and Magnesium. 



uable and promising. Dr. Macli, for ex- 

 ample, has named such alloj'S ' magnalium.' 

 Possibly other investigators may not be 

 aware that this series was long ago investi- 

 gated at the suggestion of the writer and in 

 considerable detail in the laboratories of 

 Sibley College. The writer published an 

 account of the work in 1893 and it has been 

 reproduced or summarized in several cases 

 since.* The following are the tabulated 

 results of such tests of strength of the two 

 metals and their alloys as then determined. 

 The succeeding graphic illustration of their 



* For earlier work on properties of magnesium and 

 its alloys, see ' Materials of Aeronautic Engineering, ' 

 Transactions Aeronautic Congress, Chicago, 1893 ; also 

 Sibley Journal, April, 1894.— E. H. T. 



' Magnesium as a Constructive Material. ' — R. H. T. 

 London Machinery, May, 1896 ; ' Industries and Iron,' 

 May 22, 1896. Also Thurston's ' Materials of Engi- 

 neering,' vol. iii., pp. 94-561. 



' Mechanical Properties of certain Aluminium Al- 

 loys,' R. C. Carpenter ; Trans. A. S. M. E., vol. xix., 

 1898, No. DCCLXXXIV. 



From this table it will be seen that, for 

 magnesium, the 



Average breaking strength is 22,250 lbs. per sq. in. 



Average elastic limit is 8,870 



Average elongation is 2.8 per cent. 



Average modulus of elas- 

 ticity is 1,945,000 



It is noticeable that though the density 

 of the metal is only two-thirds that of 

 aluminium it has one-half more tensile 

 strength ; the latter averaging, pure, about 

 15,000 pounds. 



The addition of magnesium to aluminium 

 reduced ductility steadily with rising pro- 

 portions and, at one-third magnesium and 

 two-thirds aluminium, the alloy was as 

 brittle as glass. Magnesium refused to 

 alloy with iron. The alloys with alumin- 

 ium, where the proportion of magnesium 

 is small, give promise of finding useful and 

 valuable applications in the arts. 



The series of tests of which the diagram 



