Interaction of Mechanical and Electrochemical Factors duringCorrosion Fatigue of Fe-26Cr-1Mo Stainless Steel in 1M H_2SO_4 Solution

The cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr1Mo stainless steel in 1M H2SO4 solution at a passive potential.The influence of plastic strain amplitude and plastic strain rate on the dissolution current response was analysed. The experimental results showed that the transient current was dependent on the competitive process of the surface film rupture and repassivation of the new surface. The high plastic strain amplitude and the high plastic strain rate caused a change of electrochemical activity of specimen surface. In the condition of low strain amplitude and strain rate, the characteristics of current response was mainly relative tp the process of new surface repassivation.The competition kinetics has been analysed through the comparison of plastic strain rate and repassivating rate

Mechanical behaviors of NiAl-Cr(Mo)-based near eutectic alloy with Ti, Hf, Nb and W additions

Effects of Ti, Hf, Nb and W alloying elements addition on the microstructure and the mechanical behaviors of NiAl-Cr（Mo） intermetallic alloy were investigated by means of XRD, SEM, EDX and compression tests. The results show that Ni-31Al-30Cr-4Mo-2（Ti, Hf, Nb, W） alloy consists of four phases： NiAl, ？？Cr solid solution, Cr2Nb and Ni2Al（Ti, Hf）. The mechanical properties are improved significantly compared with the base alloy. The compression yield strength at 1 373 K is 467 MPa and the room temperature compression ductility is 17.87% under the strain rate of 5.56？？0-3 s-1, due to the existence of Cr2Nb and Ni2Al（Ti, Hf） phases for strengthening and Ti solid solution in NiAl matrix and coarse Cr（Mo, W） solid solution phase at cellular boundaries for ductility. The elevated temperature compression deformation behavior of the alloy can be properly described by power-law equation： ε=0.898 σ8.47exp[-615/（RT）].

NiTiAl Intermetallic Alloys Strengthened by Mo Replacement

NiTiAl based alloys have attracted attention as potential high temperature structural materials. Alloying is an effective way to improve their mechanical properties. The microstructures and mechanical properties of NisoTi44-xAl6Mox （x = 0, 0.5, 1, 1.5, 3） alloys have been investigated by X-ray diffraction （XRD）, scanning electron microscope （SEM）, transmission electron microscope （TEM） and compressive tests. It is found that Ni50i44-xAl6Mox alloy is composed of NiTi （B2） and Ti2Ni （FCC） phases when Mo content is no more than 1 at%. The effect of Mo solid solution hardening at room temperature has been indicated by the rise of yield strength and the fall of plasticity with increasing Mo content. For Ni50Ti42.sAl6MOl.5 and Ni50Ti41Al6M03 alloys, a Mo solid solution appears and increases the yield strength by precipitation strengthening. The maximum yield strength at 600 ℃ and elevated temperatures is presented in Ni50Ti43A16M01 alloy not in alloys with a higher Mo content, which is possibly due to the softness of Mo-Ti-Ni solid solution phase.

Breaking the trade-off of hardness–ductility in(Cr_(1−x)Mox)_(2)AlC MAX phase coatings via a hierarchical structure

The Cr_(2)AlC MAX phase offers a remarkable combination of excellent electrical conductivity and hot corrosion resistance in extremely harsh environments.However,the strong trade-off between hardness and toughness is rather limited by its nanolaminate structure for desired applications.Taking the solid solution strengthening and gradient hardening synergy,in this work,high-purity Cr_(2)AlC coatings with various Mo solid solutions were successfully fabricated via a hybrid sputtering technique followed by subsequent annealing.Interestingly,gradually changing the Mo concentration in the(Cr_(1−x)Mox)_(2)AlC(x=0.05–0.24)coating enabled a hierarchical structure responsible for gradient refinement of the crystal grain size,and the solid solution of Mo atoms at Cr sites and the gradient variation in the Mo content were confirmed via the atomic-resolution transmission electron microscopy(TEM)characterization.Compared with those of the pristine Cr_(2)AlC coating,the nanoindentation hardness and toughness values of H/E and H_(3)/E_(2) for the hierarchical(Cr_(1−x)Mox)_(2)AlC coating were enhanced by approximately 26%,12%,and 57%,respectively.On the basis of comprehensive experiments and ab initio simulations,the reasons behind this observation were mainly attributed to the synergistic effect of Mo occupancy with strong bonding at the Cr site and the strengthening of grain refinement induced by the gradient Mo concentration in the(Cr_(1−x)Mox)_(2)AlC coating.These findings not only reveal the underlying mechanism for the Mo solid solution in the Cr_(2)AlC coating but also offer a new concept for developing ultrahigh-strength ductility materials for the laminar MAX phase.