JB/T 7946.1-2017Metallography of cast aluminium alloys - Part 1: Modification of cast aluminium-silicon alloys (English PDF)

Foreword

JB/T 7946 "Molded Aluminum Alloy Metallurgy" is divided into four parts:

- Part 1: Cast aluminum-silicon alloys modification;

- Part 2: Cast aluminum-silicon alloys burning;

- Part 3: Cast aluminum alloys pinhole;

- Part 4: Cast aluminum-copper alloys grain size. This part is the part 1 JB/T 7946.

This part replaces JB/T 7946.1-1999 "Metallograph of cast aluminum alloys - Cast aluminum-silicon alloys - Modification". As compared with JB/T 7946.1-1999, the main technical changes are as follows:

- MODIFY part of technical content on cutting and preparation of specimen;

- MODIFY the grading instructions for phosphorus modification; REPLACE the corresponding microscopic reference picture;

- ADD the grading instructions for strontium and antimony modification; ADD corresponding microscopic reference pictures.

This part was drafted in accordance with the rules given in GB/T 1.1-2009.

1 Scope

This part of JB/T 7946 specifies the cutting and preparation of metallographic specimens of cast aluminum-silicon alloys, the observation of metallographic structure, the grading of cast aluminum-silicon alloys.

This part applies to the evaluation of the grade of modification of cast aluminum-silicon alloys.

2 Normative references

The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) are applicable to this standard.

GB/T 3246.1 Inspection method for structure of wrought aluminum and aluminum alloy products - Part 1: Inspection method for microstructure

3 Cutting and preparation of specimen

4 Metallographic observation of specimen

4.1 Use an optical microscopy to observe the microstructure of the cast aluminum-silicon alloy. The magnification of metallographic structure after sodium modification, strontium modification, antimony modification is 200 times; the magnification of metallographic structure after phosphorus modification is 100 times.

4.2 First, observe the metallographic structure of the entire metallographic specimen; then evaluate it according to the level figure corresponding to the field of view of most metallographic structures.

5 Grading of cast aluminum-silicon alloy modification

5.1 The cast aluminum-silicon alloy modification is divided into no modification, insufficient modification, normal modification, deterioration of modification, mild over-modification, severe over-modification. The grading description is as shown in Table 1. The reference metallographic structure is as shown in Figure 1.

Insufficient modification alpha dendrite and eutectic are uniformly distributed, some eutectic silicon is short rod-shaped, some is needle-like Figure 1b)

Normal modification alpha dendrite and eutectic are uniformly distributed, eutectic silicon is punctate or wormlike Figure 1c)

Deterioration of modification alpha dendrite and eutectic are not uniformly distributed, eutectic silicon is thickened, some is short-rod shaped, some needle-like Figure 1d)

Mild over-modification alpha dendrite and eutectic are basically uniformly distributed, but linear alpha-belt appears in some eutectics Figure 1e)

Severe over-modification alpha dendrite and eutectic are irregularly distributed, a coarse modification zone appears (a wavy alpha-belt appears in the fine eutectic with many eutectic silicon in it) […]