Effect of Zr Addition to Aluminum Grain Refined by Ti+B on its Wear Resistance after Extrusion Condition Adnan I. O. Zaid, Safwan M. A. Al-qawabah Jordan

Aluminum is the second widely used metal due to its desirable chemical, physical and mechanical properties. It is. none toxic, none sparking, none magnetic and its appearance.. Furthermore, it has high strength-to-weight ratio, high corrosion resistance, high electrical and thermal conductivities and ease fabrication WEAR Whenever two surfaces slide or roll against each other with certain velocity under the effect of certain high efficient nuclei for Al grains. Recently, others have also suggested different mechanisms, there will be frictional resistance at the interface of the two surfaces which will result in wear.

Chemical composition (wt %) of commercially pure aluminium Chemical analysis of the Al-4.6 %Ti-0.92%B by weight

(a)Schematic drawing of the Extrusion die assembly, (b) photograph of Extrusion die

Different Micro-Alloys The binary Al-1.17wt.%Zr were prepared from commercially pure metals. In each case Ti+B was added into molten aluminum at about 1100 ْ C and stirred under crayolite flux. The aluminum and the prepared binary master alloy Al-1.17 %wt. Zr and the commercially available Al- 4.6% Ti % B were used in preparing the Al micro-alloys Al- Zr, and Al- Ti-B-Zr. Al and its micro-alloys with their chemical compositions Chemical composition of the different Al microalloys

Effect of Zirconium addition on the Grain Size of Al and Al Grain Refined by Ti+B

(a) Pure Al (124  m) (b) Al-Ti-B (83  m) (c) Al-Zr (128  m) (d)Al-Ti-B-Zr (58  m) Photomicrographs showing the Effect of Zr addition to Al and Al Grain Refined by Ti+B on its General Microstructure in the Cast Condition: at X250

(a') Pure Al (78  m)(b') Al-Ti-B( 26  m) (c') Al-Zr (46  m) (d') Al-Ti-B-Zr (18  m) Photomicrographs showing the Effect of Zr addition to Al and Al Grain Refined by Ti+B on its General Microstructure in the after extrusion at X250

True Stress-True Strain Curves of Al and its Microalloys after Extrusion

Mechanical characteristics of Al and its different microalloys after extrusion

Theoretical and experimental values of extrusion force

EXPERIMENTAL and theoretical values of the extrusion energy

Effect of Zirconium addition of Al and Al Grain Refined by Ti+B after Extrusion at (S = 0.27m/sec, loads = 10, 20 N)

Effect of Zirconium addition of Al and Al Grain Refined by Ti+B after Extrusion at (S = 3m/sec, loads = 10, 20 N)

Conclusions Addition of Zr at a rate of 0.1%wt. to Al resulted in poisoning of the grain size i.e. coursing of its grains, whereas it resulted in grain refinement of its grain when added to Al grain refined by Ti+B. furthermore, the extrusion process resulted in further refinement of the grains of Al and its microalloys. Addition of Zr to Al resulted in deterioration of its mechanical strength, whereas, it resulted in its enhancements when added to Al grain refined by Ti+B. The direct extrusion process resulted in increase of the mechanical strength of Al and all its microalloys. Furthermore, it resulted in high increase of their work hardening index, n, i.e. resulted in improvement of their formability, hence it causes reduction in the number of stages required for forming at large strains in excess of the plastic instability point before the addition. Addition of Zr to Al resulted in decrease of the extrusion force and energy requirements, whereas it resulted in high increase in them when Zr is added to Al grain refined by Ti+B. The wear tests revealed that it is not possible to conclude from them because there is no criterion exists among the obtained results at the different loads and speeds due to the presence of the plastic deformation (mushrooming) at worn end. The Archard theory failed to fit the wear results because it did not take into consideration the mushrooming effects, which in most cases it is more damaging than the mass loss. The suggested model which takes into consideration the effect of the plastic deformation at the worn end is more realistic and gives better correlation of the obtained experimental results.

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