Printed in the United Kingdom ON THE ROLLING TEXTURE REVERSAL IN FCC METALS

As all factors governing the process of the development of texture are strongly dependent on stacking fault energy, a marked influence of SFE on the wire texture and rolling texture characteristics should be expected. This relationship has been established for wires by English and Chin. Using their own experimental data, as well as those from literature, they plotted the amount of (100) wire texture component against v/Gb, being SFE, G the shear modulus, and b the Burgers vector, as shown in Figure 1. The most important conclusion drawn by the authors from this relationship is that the general trend toward larger proportions of (100) with reduced SFE is reversed for the lowest values of v/Gb. At the same time they come to the conclusion that: "this reversal is not found in rolling textures, which vary monotonically from "brass" to "copper" type with increasing SFE... However, the same factors governing wire texture differences are presumably operative in rolling as well". Recently Bunge and Tobisch in their investigations on rolling textures in -brasses with variable zinc contents revealed texture transition in terms of a relationship between {110}(001) texture component and the stacking fault energy parameter, and obtained a curve with a maximum at about the same v/Gb value as in English and Chin’s experiments. They conclude that the results confirm Wassermann’s3 theory of mechanical twinning which is responsible for the texture transition. In a previous paper Truszkowski and Kr614 have proposed the coefficient Tc as a measure of the variance of the density of {111 } poles from the mean value, which in this case is equal to one, according to

As all factors governing the process of the develop- ment of texture are strongly dependent on stacking fault energy, a marked influence of SFE on the wire texture and rolling texture characteristics should be expected.This relationship has been established for wires by English and Chin.Using their own experimental data, as well as those from literature, they plotted the amount of (100) wire texture com- ponent against v/Gb, being SFE, G the shear modulus, and b the Burgers vector, as shown in Figure 1.The most important conclusion drawn by the authors from this relationship is that the general trend toward larger proportions of (100) with reduced SFE is reversed for the lowest values of v/Gb.At the same time they come to the con- clusion that: "this reversal is not found in rolling textures, which vary monotonically from "brass" to "copper" type with increasing SFE...However, the same factors governing wire texture differences are presumably operative in rolling as well".
Recently Bunge and Tobisch 2 in their investiga- tions on rolling textures in -brasses with variable zinc contents revealed texture transition in terms of a relationship between {110}(001) texture com- ponent and the stacking fault energy parameter, and obtained a curve with a maximum at about the same v/Gb value as in English and Chin's experi- ments.They conclude that the results confirm Wassermann's3 theory of mechanical twinning which is responsible for the texture transi- tion.
In a previous paper Truszkowski and Kr614 have proposed the coefficient Tc as a measure of the variance of the density of {111 } poles from the mean value, which in this case is equal to one, according to Tc P,(1 Ii) 2 (1 where Pi is the fraction of the equal area { 111 } pole figure with the pole density equal to It.For random orientation, Tc O. 141 Experiments carried out on cold rolling of several fcc metals with a random orientation have revealed the linear change of Tc with the degree of percentage cold deformation z.In the case of aluminium with a sharp cube texture as the starting material, a method has been elaborated to calculate the straight line function Tc =f(z) for /he case of random orientation in the annealed state.A counterpart of a close-to-random orientation at z 0 is a very low value of To.The straight line relationship made possible the calculation of its slope mr, which represents the sensitivity of the metal or alloy to the formation of preferred orientation during cold rolling.It was established that m has a constant value over a wide range of rolling reduction (from 0 up to above 90 per cent), therefore it constitutes an essential characteristic from the point of view of the ability of a fcc metal to form privileged orientation.Consequently, it can be expected that its dependence on stacking fault energy should reveal the rolling texture reversal.The respective mt values for copper, nickel, aluminium, ' silver and 80-20 brass 6 are listed in Table I.
The function mt f(v/Gb) determined from the experimental data is shown in Figure 2.Here the values for pure metals were adopted from the recent critical survey of Gallagher 7 and for 80-20 brass from Alers and Liu. 8 A steep increase of mt values is seen within the range up to about y/Gb 5.10-3 followed by its subsequent decrease.
A more precise determination of abscissa corre- sponding to the maximum is, however, impossible because of difficulties in selecting the most credible values of SFE from the literature, and too small a number of experimental points over the considered range.This would demand investigations on metals or alloys for which 7/Gb would cover the range 5_10.10 -3.
The lack of evidence of the rolling texture reversal in many authors' earlier investigations should be ascribed to the fact that a quantitative criterion of privileged orientation in sheets was not taken into consideration.

FIGURE
Wire textures of various fcc metals and alloys as a function of the parameter 7/Gb, according to English and Chin1.

FIGURE 2
FIGURE 2 mt vs y/Gb plot for cold rolled fcc metals and alloys.

TABLE I m
, values of fee metals examined