Typical hypo- and hyper-eutectic alloys grown by impurity-mod- ified conventional casting exhibit a microstructure comprising of primary Si that assumes sizes on the order of 10-4
m. These properties of the microstructure
m and eu-
tectic silicon with a rather course fibrous morphology of sizes on the order of 10-6
have not provided ultra-high strength and fracture toughness for such as cast alloys. Recently a new procedure based upon the concept of the solubility of barium (Ba) in the silicon phase has demonstrated that a hypereutectic Al-17wt%-Si alloy can be produced without a primary Si phase being present.
This work will establish the capability of the present process of refinement with respect to the required Ba additions, Si content, and refined microstructure in hypo-eutectic Al-Si alloys. In such pursuits using permanent mold casting techniques, the freez- ing parameters for an alloy that requires the optimum amount of Ba and that reveals nano-sized microstructure will be deter- mined. Thus determined freezing parameters and Ba content will be subjected to another round of permanent mold cast- ings in which various commercially available light weight Al-Si hypo-eutectic alloys will be used as starting materials. All such cast alloys will be subjected to T6 heat treatment conditions whereupon mechanical properties of the resulting tempered al- loys will be determined. It is expected that a comparison of the mechanical properties of these alloys with those known for the commercially available light weight alloys may reveal the scale of improvement in the mechanical properties of the alloys grown by the proposed method. In establishing this capability some concentration will also be given to the related freezing pa- rameters such as under-cooling (ΔT), growth velocity (R), and the inter-lamellar spacing (λ) with the microstructure of the re- sulting alloys. Such determination is of importance with respect to the application of this technology to foundry castings of Al-Si alloys of improved mechanical properties.
Status Update: The project is now underway with the first portion of the design of experiment matrix of silicon ranges and Ba alloy additions having been tested demonstrating the refinement to the silicon morphology. The work is being moni- tored by the AFS Aluminum Division 2. Those wishing more information about the project or how to participate as a spon- sor should contact the Steering Committee chair Dave Weiss at
david.weiss@eckindustries.com or the PI Dr. Shamsuzzoha, at
shamsuz@aalan.ua.edu.
Phos-Copper Replacement Research Project (13-14#02)
Coordinator: The co-PI’s for this project are Drs. David Schwam of CWRU, Kumar Sadayappan of Canmet and David Neff, retired from Pyrotek and the AFS Copper Division 3
Phos-copper is presently used with good results to de-oxidize a wide range of copper alloys. The phosphorus has a stronger af- finity to oxygen than the molten copper alloy. It will react with oxygen to form an insoluble phosphorus-oxygen compound,
thus removing it from the melt and preventing it from reacting during solidification with hydrogen to form water vapor. It is common practice in many foundries to add about 0.15% P-Cu to the pouring ladle. This is not necessarily a good practice, since the correct addition is foundry-specific and should be de- termined on a case-by-case basis. Insufficient deoxidizer may expose the molten metal to re-oxidation during pouring, due to moisture. High residual phosphorus is also deleterious in a melt. A residual phosphorus level of 0.015-0.03% is practical for many foundries.
The metalcasting industry is concerned that a shortage in phos-copper supply could be disruptive and therefore would like to identify an appropriate substitute. Division 3 is looking for a suitable alternative de-oxidation material for these various grades of brass and bronze alloys in the event phos-copper becomes in short supply due to raw material problems.
The objectives and deliverables as set by the Copper Division for Phase 1 of the project include the following items:
a. Review of old research already performed on this topic [to avoid re-inventing the wheel]
b. Literature search of current research/developments c. Screen for toxicity concerns d. Availability of the additive e. Ease of adding the de-oxidizer into the molten metal f.
Efficiency of oxygen removal
g. The impact on fluidity, as measured in a spiral fluid- ity mold. “Equivalent” type of fluidity tests can be dis- cussed during the quotation process.
h. Effect of residual trace in casting and in revert stream i. Amount of fading upon remelting poured castings j.
List of current price of additive [based on what lot size?]
Phase 1 of this project is a systematic benchmarking and screen- ing effort in which a number of de-oxidizers will be evaluated for each alloy. The de-oxidation potency of these de-oxidizers will be compared to phos-copper. The fluidity testing method will be calibrated and validated against post-melting LECO ox- ygen analysis. Phase 1 of the project will establish the required experimental methods and procedures and carry out prelimi- nary screening of deoxidizers.
Status Update: The project is now underway and the steering committee has been very active working with CWRU. The work is being monitored by the AFS Copper Division 2. Those wish- ing more information about the project or how to participate as a sponsor should contact the Steering Committee Chair, Sylvia Canino at
scanino@colonialmetalsco.com or the Principal-PI Dr. David Schwam at
dxs11@case.edu.
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International Journal of Metalcasting/Volume 8, Issue 2, 2014
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