THE HARDNESS BEHAVIOR OF CHROMIUM ALLOYED WITH GROUP IV-A TO VIII TRANSITION METALS
The room-temperature hardness of iodide chromium containing binary additions of Group IV-A to VIII metals (Ti, Zr, Hf, V, Nb, Ta, Mo, W, Mn, Re, Fe, Ni, Co, Ru, Rh, Pd, Os, Ir, and Pt) up to 65 at. % was investigated. Each alloy series, as arc-cast or homogenized, showed a hardness minimum as a function of alloy concentration near 0.5 at. %. The initial softening amounted to 1 to 20% and was followed by solid-solution hardening. Softening by lowering the elastic modulus or changing the nature of grain boundaries by alloying appeared minor. A plausible explanation based on thermodynamic evidence suggests alloying decreases interstitial solubility. Thus interstitial compound formation takes place at a higher temperature, thereby making agglomeration kinetically more favorable and resulting in overaging and softening. Furthermore, the softening effect was similar in magnitude to nitrogeninduced quench hardening. Group VII-A and VIII but not IV-A to VI-A additions to Cr at about the solid-solubility limits tended to cause mechanical twinning about hardness impressions. Paralleling reported results for W and Mo, increasing the average group number above 8 promotes twinning and suggests alloying decreases the twin boundary energy. Large solid- solution additions of Re to Cr caused significant increases in hardness up to 1100 deg C. A characteristic hardness break was exhibited at about half the absolute solidus temperature. (auth)
- Research Organization:
- Battelle Memorial Inst., Columbus, Ohio
- NSA Number:
- NSA-17-037548
- OSTI ID:
- 4646982
- Journal Information:
- Trans. Am. Soc. Metals, Vol. Vol: 56; Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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