Effects of Ce-Rich Mischmetal on Microstructure Evolution and Mechanical Properties of 5182 Aluminum Alloy

This paper addresses the effects of Ce-rich mischmetal on the microstructure evolution of a 5182 aluminum alloy during annealing and rolling processes. The Ce-rich mischmetal was added to an as-cast 5182 aluminum alloy in an induction furnace, and this was followed by homogenized annealing at 450 °C for 24 h and a rolling operation. The microstructure evolution and mechanical properties’ analysis of the 5182 Al alloy were characterized. The results show that the Ce-rich mischmetal could modify the microstructure, refine the α-Al grains, break the network distribution of Mg2Si phases, and prevent Cr and Si atoms from diffusing into the Al6(Mn, Fe) phase in the as-cast 5182 Al alloys. Ce-rich mischmetal elements were also found to refine the Al6(Mn, Fe) phase after cold rolling. Then, the refined Al6(Mn, Fe) particles inhibited the growth of recrystallization grains to refine them from 10.01 to 7.18 μm after cold rolling. Consequently, the tensile strength of the cold-rolled 5182 Al alloy increased from 414.65 to 454.34 MPa through cell-size strengthening, dislocation density strengthening, and particle strengthening. The tensile strength of the recrystallization annealed 5182 Al alloy was increased from 322.16 to 342.73 MPa through grain refinement strengthening, and this alloy was more stable after the recrystallization annealing temperature.

Grain Refinement Strengthening of Sm in AZ61 Alloy

The grain refinement and relative strengthening of rare earth element Sm in magnesium alloy AZ61 has been investigated. The results show that high melting point Al2Sm phase forms in AZ61 alloy with the addition of 2wt.% Sm. It leads to the refinement of grain size and enhances the strength of AZ61 alloy.

Effects of Nano-Al2O3 on the Mechanical Property and Microstructure of Nano-Micro Composite Self-Lubricating Ceramic Tool Material

A new nanomicro composite self-lubricating ceramic tool material was prepared with vacuum hot pressing technique. The effect of nanoAl2O3 powders on the microstructure and mechanical properties of nanomicro composite self-lubricating ceramic tool material was investigated. With the increase of nanoAl2O3 content, the hardness and fracture toughness first up then down. When the nanoAl2O3 content is 4 vol.%, the flexural strength, hardness and fracture toughness reaches 562 MPa, 8.46 MPa·m1/2 and 18.95 GPa, respectively. The microstructure and mechanical property of nanomicro composite self-lubricating ceramic tool material can be improved by the grain refinement strengthening of nanoAl2O3.

Effect of Operating Temperature on Direct Recycling Aluminium Chips (AA6061) in Hot Press Forging Process

A method of solid-state recycling aluminum alloy using hot press forging process was studied as well as the possibility of the recycled chip to be used as secondary resources. This paper presents the results of recycled AA6061 aluminium alloy chip using different operating temperature for hot press forging process. Mechanical properties and microstructure of the recycled specimens and as-received (reference) specimen were investigated. The recycled specimens exhibit a good potential in the strength properties. The result for yield strength (YS) and ultimate tensile strength (UTS) at the minimum temperature 430°C is 25.8 MPa and 27.13 MPa. For the maximum operating temperature 520°C YS and UTS are 107.0MPa and 117.53 MPa. Analysis for different operating temperatures shows that the higher temperatures giving better result on mechanical properties and finer microstructure. The strength of recycled specimen increases due to the grain refinement strengthening whereas particle dispersion strengthening has minor effects. In this study, the recycled AA6061 chip shows the good potential in strengthening as the comparison of using only 17.5% of suggested pressure (70.0/400.0) MPa, the UTS exhibit 35.8% (117.58/327.69) MPa. This shows a remarkable potential of direct recycling by using hot press forging process.

Challenges in Manufacturing Aluminium Based Metal Matrix Nanocomposites via Stir Casting Route

The influence of material processing conditions for preparing aluminium based metal matrix nanocomposites through stir casting route is reviewed. The role of particle size with respect to Brownian motion, Stokes settling velocity and strengthening mechanism is assessed from theoretical understandings. Variation of microstructural features and mechanical properties of the nanocomposites are predicted from theoretical concepts and related mathematical models. Experiments conducted to validate the theoretical predictions show that both Orowan and grain refinement strengthening mechanisms remain operative which is the key to the improved strength property of the nanocomposites.

Influence of Chromium on the Hall-Petch Coefficient in Ferritic Steel

In ferritic stainless steels, the amount of Cr is moderately controlled to have good corrosion resistance in applied environment. However, it also affects the yield strength of ferritic stainless steels through solid solution strengthening and grain refinement strengthening. Until now, some researches have been performed using commercial stainless steels but the obtained results contain the effect of solute interstitials (C and N). In this paper, the influence of Cr on the above both strengthening mechanism was discussed by using interstitial free ferritic stainless steel in which carbon and nitrogen are completely fixed as Ti(C,N). A previous paper has reported that the addition of chromium gives different influences to the Hall-Petch coefficient depending on the amount of Cr. However, our research has reveals the fact that the change of Hall-Petch coefficient is not due to the effect of chromium but due to small amount of carbon which exists as an impurity in ferritic stainless steels. It was concluded that chromium itself does not give any influence to the Hall-Petch coefficient of ferritic iron.

Strengthening Mechanisms of Vanadium Micro-Alloyed Reinforcing Steel Bar

High strength vanadium micro-alloyed steel with yield strength of 600MPa has been developed based on commercial 20MnSi steel bar. Experimental methods, such as OM, SEM and TEM, were used to study the experimental steels. Compared with 20MnSi, steel 20MnSiV boasts much finer microstructure, and large numbers of nanometer precipitates exist in the specimens of 20MnSiV. Analysis shows that strength of 20MnSiV dramatically increases through grain refinement strengthening and precipitation hardening of nanometer VCN particles.

The Grain Refining and Strengthening Mechanism of C-Mn Steel by CSP

The grain refining of C-Mn steel on CSP line was investigated in this paper. The grain size was about 100μm after rolling by stand F1 and then decreased all the way of the rolling process(stands F2-F6) to 15μm. The strengthening mechanisms, grain refinement strengthening, solution strengthening, precipitation strengthening and dislocation strengthening, were figured out to develop a physical metallurgy model for prediction of the properties. It was noted that there is an agreement between the predicted properties and the measured ones of the steel.