Effect of scandium and titanium–boron on grain refinement and hot cracking of aluminium alloy 7108

Abstract

The effect of scandium and titanium–boron (Tibor) additions on the solidification behaviour of castings and welds of aluminium alloy 7108 has been investigated. A circular patch test was adopted to evaluate the effects of these elements on the hot cracking suscepti bility of welds made on cast coupons treated with different grain refiner additions. It was observed that grain size, as well as cracking susceptibility, decreased with increasing amounts of scandium and that hot cracking was completely eliminated at scandium additions above 0·25 wt-%. A more pronounced grain refining effect in welds was observed with Tibor and, in addition, no hot cracking was observed with Tibor additions as low as 0·02 wt-%Ti (0·004 wt-%B). Castings, however, were more effectively grain refined with scandium, achieving a finer grain size than with Tibor.

Multistep nucleation and multi-modification effect of Sc in hypoeutectic Al-Mg-Si alloys

“…Thus even a small concentrations of transition elements have a large impact on the structure and properties of Al alloys. Sc has been successfully used as a minor alloying element not only as grain refiner, but also to prevent hot-cracking susceptibility and increase corrosion resistance in aluminum alloys [8, 9, 10, 11, 12]. Hence, among all transition elements, Sc is the most prospective addition to Al alloys.…”

Weld Parameter and Minor Element Effects on Solidification Crack Initiation in Aluminium

“…The grain refiner addition significantly improved weldability, particularly at low 4043 dilutions. This is not surprising considering the potent effect of refinement reported for aluminium weldability improvement [29]. Moreover, it seems that TiBor improves weldability with more efficiency than 4043, the boundary being completely moved to higher strain rates for all dilutions.…”

“…Reduced cracking susceptibility of aluminium alloy 7108 has been related to grain refinement, adding grain refiners scandium and titanium-boron, i.e. TiBor [29]. Using the circular patch test, cracking was avoided when adding a minimum of 0.25 wt.%Sc or (0.02 wt.%Ti + 0.004 wt.%B), corresponding respectively to a grain size 80 μm and 180 μm.…”

Düşük Alaşımlı Çelik Kaynaklarda Sıcak Çatlak Oluşumunun Matematiksel Olarak Modellenmesi

“…Skandiyum (Sc) ve Titanyum (Ti) gibi elementlerin ise sıcak çatlamayı önleyebildiği düşünülmektedir [9]. Bilimsel yazımda, sıcak çatlama dayanımın test edilmesine yönelik farklı birçok yöntem önerilmiştir.…”