Constant modulus alloys for mechanical oscillators
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taken t o achieve constant modulus behavior, e.g. ternary alloying elements, cold reduction, t h e r m a l treatment. II. TECHNICAL ALLOYS The addition of ternary elements such as Mo or Cr reduces the e n t i r e modulus defect, which straightens the temperature curve and shifts it to a somewhat h i g h e r l e v e l4 ( F i g . 3). Prototypes of such alloys are: "Vibralloy" 40 pct Ni, 9 pct Mo, balance F e " E l i n v a r " 36 pct Ni, 12 pct Cr, balance Fe.
Reduction of the shape magnetostrictive component is achieved by a strong magnetic f i e l d or increased hardness. However, for other reasons m a x i m u m cold work is not desirable. Under such circumstances optimum results are obtained by precipitation hardening u s i n g additions of T i + A1 or Be. S i n c e precipitation hardening-forming Nis(Ti,A1) or N i B e - influences the effective Ni content of the matrix, the temperature coefficient (TC) can easily be adjusted t o the optimum value. Such alloys are, for instance,"Thermelast" and " N i Span C". Table I shows a list of c o m m e r c i a l constant modulus alloys of m a j o r technical importance. All these alloys are F e - N i b a s e d and ferromagnetic. Besides t h e s e types there are a lot of modifications using further additions, e.g. W, V, Nb, C and variations of the Cr or Mo content.6 The above theory applies equally to the s h e a r modulus G. It should not surprise, however, that the temperature independence of the s h e a r modulus is obtained for zkE = AEA + ~tEk + AE~. slightly different compositions. As an example Fig. 4 zkEA is due t o the spontaneous volume magnetostricshows typical dynamic measurements of the moduli for tion. the two c o m m e r c i a l alloys Thermelast 5409 and AEk results from the orientation of the magnetic doThermelast 4290.5 m a i n s which is induced by the e l a s t i c stresses The variation of longitudinal or torsional resonance (shape magnetostriction). This produces an adfrequency with temperature is a practical m e a s u r e ditional elongation in a nonsaturated material. for the dependence of the elastic modulus E or the zkE¢o is due t o s t r e s s induced alteration of interatomic s h e a r modulus G. T h e r e is optimum temperature distances which affects the coupling forces and compensation for the longitudinal mode (modulus E) produces a s m a l l volume effect. in Thermelast 5409 and optimum compensation for the torsional mode (shear modulus G) in Thermelast 4290. In view of these effects further m e a s u r e s must be The values of the T C ' s are in the r a n g e of 1 ppm//K. F i g u r e 5 shows the influence of the precipitation WOLFGANG SCHNEIDER and HANS THOMAS are with Research hardening process on hardness HV, velocity of sound c and Development Department, VACUUMSCHMELZE GMBH, D-6450 (instead of the elastic modulus E), TC, and Q-factor Hanau, West Germany. for Thermelast 5409. Increasing the temperature in Manuscript submitted August 4, 1978. ISSN 0360-2133/79/0411-0433500.75/0 METALLURGICAL TRANSACTIONS A © 1979 AMERICAN SOCIETY FOR MET
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