EFFECT OF MELT OVER-HEATING AND ZIRCONIUM ALLOYING ON THE MORPHOLOGY OF Al_9FeNi PHASE AND MECHANICAL PROPERTIES OF 2618 ALLOY

The effect of melt over-heating on the morphology of Al_9FeNi phase in 2618aluminum alloy with high contents of Fe and Ni and 0.22 wt. percent zirconium has been investigatedby optical microscopy. SEM and TEM. The mechanical properties of 2618 aluminum alloy after hotextrusion and quenching/aging have been tested. The results show: melt over-heating treatment of2618 alloy with high contents of Fe and Ni at 960 deg C led to finer and better-distributedneedle-like Al_9FeNi phase in cast microstructure and fine Al_9FeNi particles after hot extrusion;the grain size of the alloy after hot extrusion could also be refined evidently by alloying ofzirconium; the ambient and high temperature tensile strength and elongation of 2618 alloy have beenapparently enhanced due to fine Al_9FeNi particles and dispersed Al_3Zr as well as fine grain size.

Experimental study and numerical analysis on dry friction and wear performance of co-continuous SiC/Fe-40Cr against SiC/2618 Al alloy composites

The dry friction and wear behaviors of co-continuous composites SiC/Fe–40Cr against SiC/Al 2618 alloy were investigated on a ring-on-ring friction and wear tester at sliding speed of 30-105 m/s under the load of 1.0-2.5 MPa. The experimental result reveals that the characteristic of two body abrasive wear and oxidation wear mechanisms are present for SiCn/2618 Al composite under higher load and sliding speed. SiC ceramic continuous network as the reinforcement can avoid composite from the third body wear that usually occurs in traditional particle reinforced composite. The mechanically mixed layer (MML) controls greatly the wear rate and friction coefficient of the composites. The composites tested at higher sliding speed exhibit higher value of friction coefficient and fluctuation, which is associated with the intermittent formation and removal of the MML. The wear and stress—strain behaviors of SiCn/Fe–40Cr against SiCn/Al 2168 at 30-105 m/s under 1.0-2.5 MPa were analyzed by finite element method with the software Solidwork2012 Simulation, respectively. The wear and stress–strain behavior of the composite predicted by the FEM correlated well with the experimental results.

Effect of Trace Sc and Zr on the Mechanical Properties and Microstructure of A1 Alloy 2618

An experimental 2618(Al-Cu-Mg-Fe-Ni) alloy added with trace Sc and Zr was prepared by ingot metallurgy (IM) method. The aging behavior of the alloy was studied by Vickers hardness measurement at 200℃ and 300℃. and the tensile properties of alloy specimens were measured at 20℃, 200℃, 250℃ and 300℃. The microstructure was observed by using optical microscope, SEM and TEM. It was found that the addition of Sc and Zr to 2618 alloy resulted in a primary Al_3(Sc,Zr) phase which could refine the grain because it acts as nuclei of heterogeneous crystallization in the melt during solidification. The secondary Al_3(Sc,Zr) particles were full coherent with matrix and had obvious precipitation hardening effect. They also made the S' phase precipitate more homogeneous. So the strength of alloy increases at both ambient and elevated temperatures without a decrease of ductility. The ductile fracture of alloy occurs by microvoid nucleation, growth and coalescence, so the microvoid coalescence is the dominant fracture mechanism.

Analysis of the Cross-Wedge Rolling Process of Toothed Shafts Made from 2618 Aluminium Alloy

The paper presents the results of a thermo-mechanical analysis of the rolling two stepped shafts.One of the shafts has a toothed step with skew teeth,while the other has a worm winding in the shape of a trapezoidal screw.The shape of the rolling tools resembles that of the tools used in the Roto-Flo rolling method;yet unlike in Roto-Flo,the shafts are hot-rolled and no centres are used to stabilize the position of the workpiece during the forming process.For the calculations made with use of the DEFORM-3D process simulation system it has been assumed that the rolled shafts are made from 2618 aluminium alloy.As a result of the calculations made,it has been found that the toothed stepped shafts can be formed in one pass by means of the cross rolling process.Additionally,the temperature and strain distribution in the rolled product have been determined as well as some data concerning the forces which are necessary for the rolling process have been obtained.