Hot Tearing in Cast Aluminum Alloys

Abstract

MPI and CANMET, both members of the Light Metal Alliance, launched a research project to study hot tearing in aluminum alloys. In this project, a reliable test method to quantitatively evaluate hot tearing was developed, and the processing variables affecting hot tearing tendency were also investigated. This paper summarizes the outcomes of this work from the following aspects: 1) Critical literature survey; 2) Experimental set-up, test methodology and procedures; 3) Effects of mold temperature and pouring temperature; 4) Effect of grain refinement; 5) Thermomechanical simulation of hot tearing.

A criterion for cracking during solidification

“…7a predicts the significantly higher crack susceptibility of alloy A206 than A356. This prediction is consistent with the known high crack susceptibility of A206 and low crack susceptibility of A356 in casting practice [35][36][37], which can also be seen in the results of the constrained-rod casting in Fig. 7b [38].…”

Hot Tearing Susceptibility of AA3000 Aluminum Alloy Containing Cu, Ti, and Zr

“…These cracks are usually visible to the naked eye, and the ingots must be scrapped to prevent failures in further processing. [1][2][3] Studies of hot tearing have resulted in several theories about the mechanisms of crack nucleation and propagation involving metallurgical and thermo-mechanical factors. The key factors for hot tearing are liquid film and inadequate eutectic feeding in the last stage of solidification, together with thermally induced stress-strain, which cannot be accommodated by the semi-solid material.…”

“…The key factors for hot tearing are liquid film and inadequate eutectic feeding in the last stage of solidification, together with thermally induced stress-strain, which cannot be accommodated by the semi-solid material. [1,[4][5][6][7] Hot tearing susceptibility (HTS) is highly dependent on the chemical compositions of Al alloys, and is described as a lambda curve for binary alloys. In most binary alloys, an initial increase in solute content (start of the lambda curve) enlarges the solidification interval.…”

A new investigated method on hot tearing behavior in aluminum alloys

“…Various measurement techniques or experimental apparatus are summarized by Eskin [11] et al in their reviews, which include ring type testing, backbone mold testing, cold finger testing, tensile test ing and so on. The N Tec hot tearing mold testing is a variation of the backbone mold testing, which is devel oped by N Tec Ltd. in Canada [12]. Instone et al develop a constrained solidification test rig for charac terizing tensile strength development and hot tearing behavior of solidifying material [2,13].…”

“…Instone et al develop a constrained solidification test rig for charac terizing tensile strength development and hot tearing behavior of solidifying material [2,13]. The research group at MPI in USA and CANMET in Canada has developed the instrumented constrained rod mold testing [12]. L. Bichler et al use neutron diffraction techniques in assessing hot tearing in magnesium alloy castings and the ex situ residual stresses and strains associated with initiation of hot tearing are measured [14].…”