No abstract

No abstract

This paper focuses on the Fe59.5Ni28Al11.5Ta1 memory alloy, in which the effects of different aging treatments on microstructure and properties of the rolled alloy are investigated by metallurgical microscope, X-ray diffraction, SEM, EDS and pressure test machine. Results show that, because of aging treatment, precipitation of γ’ and β’ phase strengthens the austenitic matrix. With the increase of aging time at 600 ℃, the comprehensive analysis of pseudoelasticity curve, shows that the stress-induced martensite critical stress of the aging state of the alloy decreases first and then increases; the alloy compressive strength, the recoverable strain and the hardness increase first and then decrease, Besides, the alloy residual strain is first decreased and then increased. When the aging time is 60 h, the alloy compressive strength is the maximum, up to 1306 MPa, the alloy recoverable deformation is the maximum, reaching 14.9%, the hardness of the alloy is also the largest, but the alloy residual strain is relative minimum. With the increase of aging time, alloy maximum strain decreases gradually, and the plasticity of the alloy also decreases gradually. The properties of the shape memory alloy are influenced by the particle size, its distribution, volume fraction, of precipitate phase etc.

With the Uddeholm self-restricted method, the effect of compound layer of plasma nitriding on thermal fatigue behavior of 4Cr5MoSiV1 steel was studied by the way of adding Ar during plasma nitriding to remove the compound layer. The results show that the compound layer of plasma nitriding can delay the nucleation of heat cracks and hold back the propagation of heat cracks from surface to substrate because of its high hardness and strength. On the other land, the heat checking expands faster with the compound layer on the surface than that without it. After 3000 cycles of thermal fatigue test, both heat cracks with the compound layer are wider than the another without compound layer and the number of heat cracks of the former is more from the view of cross section.

No abstract