Hot Deformation Behavior of a Beta Metastable TMZF Alloy: Microstructural and Constitutive Phenomenological Analysis

A metastable beta TMZF alloy was tested by isothermal compression under different conditions of deformation temperature (923 to 1173 K), strain rate (0.172, 1.72, and 17.2 s−1), and a constant strain of 0.8. Stress–strain curves, constitutive constants calculations, and microstructural analysis were performed to understand the alloy’s hot working behavior in regards to the softening and hardening mechanisms operating during deformation. The primary softening mechanism was dynamic recovery, promoting dynamic recrystallization delay during deformation at higher temperatures and low strain rates. Mechanical twinning was an essential deformation mechanism of this alloy, being observed on a nanometric scale. Spinodal decomposition evidence was found to occur during hot deformation. Different models of phenomenological constitutive equations were tested to verify the effectiveness of flow stress prediction. The stress exponent n, derived from the strain-compensated Arrhenius-type constitutive model, presented values that point to the occurrence of internal stress at the beginning of the deformation, related to complex interactions of dislocations and dispersed phases.

Improvement of Method and Mechanism for Conical and Paraboloid Springs Hardening

The disadvantage of the known methods of hardening springs is the impossibility of their use when hardening springs of a conical shape or of a shape of a paraboloid of rotation, since they are intended only for cylindrical shape springs and are not suitable for conical shape springs or those of a shape of a paraboloid of rotation specifically because of the difference in the shape of the springs. One of the disadvantages of the known springs hardening mechanisms is the impossibility of hardening the inner surface of the conical compression springs. A new method of hardening springs is proposed, the unmatched advantage of which is the ability to create plastic deformations on the inner and outer surfaces of the spring coils compressed to contact and on the surfaces along the line of contact between the coils. A new advantageous mechanism for hardening springs is proposed, which makes it possible to harden the inner surface of compression springs having a conical shape or a paraboloid shape of rotation, in a compressed state.