材料导论 (26)

Module 4 (Metallic Materials金属材料)

Video 4 Powder Metallurgy粉末冶金

Hello every one. Today, let us talk about Powder Metallurgy. 今天我们来谈谈粉末冶金.

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大家好！今天我们来谈谈粉末冶金。

What is Powder Metallurgy?

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什么是粉末冶金?

Powder metallurgy (PM), frequently designated as P/M, is a technology, which involves converting the starting material to the required powder form, and then “sticking”the material back together again to produce a more or less solid object. Powdered metals can be ferrous, nonferrous, or a combination of ferrous and nonferrous elements with nonmetallic elements.

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粉末冶金通常也用P/M代表，该技术首先采用的材料为粉末状态，再将粉体材料通过“粘接”形成固体状。粉体金属可以是黑色金属、有色金属，或者黑色或有色金属元素与非金属元素的结合。

Then,how about powder metallurgy process?

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那么，粉末冶金工艺包括哪些呢？有缘学习更多驾卫星ｙｇｄ３０７６

The PM production technologies generally involve all or most of the following process steps:powder production,mixing of powders,forming of the mixed powder into a compact,sintering of the compact to enhance integrity and strength,and secondary operations.

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PM制备技术通常涉及以下步骤：粉体制备，粉体混合，将混合的粉体压制，将压缩件烧结以提高其整体性和强度，以及其它附加工艺。

Among of them, the three basic steps are: powder mixing (or powder blending)

粉末混合, powder compaction粉末压制, and sintering烧结.

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以上几个部分中，有三个基本步骤：粉末混合，粉末压制以及烧结.

Powders may be prepared by crushing, grinding, chemical reactions, or electrolytic deposition.

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粉体可以通过压碎、研磨、化学反应或电沉积制备.

Powder compaction is the process of compacting metal powder in a die模具, through the application of high pressures, generally performed at room temperature. The density of the compacted powder increases with the amount of pressure applied.

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粉体压制是将金属粉体先在模具中压制，再通过在室温条件下施加高压而完成的。压缩粉体的密度随所施加压力的增加而增加。

Sintering is a heat treatment applied to a powder compact in order to impart strength and integrity, usually conducted at atmospheric pressure and in a protective atmosphere.

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烧结是施加于粉体压制件的热处理过程。用于提高制件强度和完整性。通常在保护性气体和大气压下完成。

Secondary operation is optional, such as coining or heat treatment热处理, often follows the sintering processing, to obtain special properties or enhanced precision.

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附加工艺可依情况而选。比如，压印或热处理常用于烧结工艺后，用于得到精准或特定性能。

There are several other PM processes, which have been developed over the last fifty years. These include: powder forging, hot isostatic pressing, metal injection moulding, electric current assisted sintering, and additive manufacturing.

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还有些其它的PM工艺，在过去的50年得到发展。包括：粉末锻造，热等静

压，金属注射成型，电流辅助烧结以及叠加制造。

Additive manufacturing is a relatively novel family of techniques, which use metal powders (among other materials, such as plastics) to make parts by laser sintering or melting. This is a process under rapid development as of 2015 year, and whether to classify it as a PM process, is perhaps uncertain at this stage. Processes include 3D printing, selective laser sintering, selective laser melting, and electron beam melting.

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叠加制造是一种非常新的制造技术。该技术通过激光烧结熔融将金属粉体粘结成块。该工艺在2015年得到了迅猛发展，然而并不十分确定将其归类于粉末冶金。加工工艺还包括3D打印，选择性激光烧结，选择性激光熔融以及电子束熔融。

PM processes can avoid, or greatly reduce the need to use metal removal processes, thereby drastically reducing yield losses in manufacture, and often resulting in lower costs. Powder metallurgy is also used to make unique materials impossible to get from melting or forming in other ways.

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在制备过程中，PM工艺可以避免或减少切削金属工艺进而大大减少金属的损耗，因而制备成本低。粉末冶金常用于制备熔融或采用其它成型工艺所不能完成的金属材料。

The benefits of using PM to make components are as follows:

※ Structural pieces with complex shapes

※ Special properties such as hardness and wear resistance

※ Great precision and good surface finish

※ Reduced component weight

※ Controlled porosity

※ Controlled performance

※ Good performance in stress and absorbing of vibrations

※ Large series of pieces with narrow tolerances