<PAGE>

                                                                      EXHIBIT 4k

                        FIRST AMENDMENT TO LOAN AGREEMENT

         This FIRST AMENDMENT TO LOAN AGREEMENT (this "Amendment") is made and
entered on February 1, 2005, and made effective as of December 22, 2004 (the
"Effective Date"), by and among Brush Engineered Materials Inc., an Ohio
corporation (the "Borrower"), each of the other Credit Parties (as defined in
the Loan Agreement (as defined below)), the Required Lender (as defined in the
Loan Agreement), and Guggenheim Corporate Funding, LLC, as collateral agent (the
"Agent").

                                   BACKGROUND

A.       The Borrower, the other Credit Parties, the Required Lender and the
         Agent are party to that certain Loan Agreement, dated as of December 4,
         2003 (as may be amended, restated, modified or supplemented from time
         to time, the "Loan Agreement").

B.       The Borrower, the other Credit Parties, the Required Lender and the
         Agent desire to amend certain provisions of the Loan Agreement as set
         forth in and pursuant to the terms and conditions of this Amendment.

C.       Capitalized terms used but not defined in this Amendment shall have the
         meanings given to them in the Loan Agreement.

                               TERMS OF AMENDMENT

         NOW, THEREFORE, for valuable consideration received to their mutual
satisfaction, the parties hereby agree as follows:

1.       Amendments to Section 1 of the Loan Agreement.

         (a)      The definitions of "Maximum Bank One Debt" and "Permitted
                  Precious Metals Agreements" set forth in Section 1 of the Loan
                  Agreement are hereby deleted in their entirety and replaced
                  with the following:

                                    "Maximum Bank One Debt" means the sum of (i)
                           the aggregate outstanding principal amount of Bank
                           One Revolving Loans and letter of credit
                           accommodations made or issued pursuant to the Bank
                           One Debt Documents, Rate Management Obligations and
                           Banking Services Obligations equal to the lesser of
                           (A) (1) $117,500,000 less (2) the aggregate
                           outstanding principal amount of the Bank One Term
                           Loans outstanding on the date hereof as reduced from
                           time to time by voluntary principal payments and
                           prepayments of such Bank One Term Loans pursuant to
                           the terms of the Bank One Debt Documents and (B) 105%
                           of Availability in effect as of the date of the last
                           Advance or

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                           issuance of a Letter of Credit (as such terms are
                           defined in the Bank One Credit Agreement) plus (ii)
                           the aggregate outstanding principal amount of the
                           Bank One Term Loans made pursuant to the Bank One
                           Debt Documents equal to the principal amount of the
                           Bank One Term Loans outstanding on the date hereof as
                           reduced from time to time by voluntary or scheduled
                           principal payments and prepayments of such Bank One
                           Term Loans pursuant to the terms of the Bank One Debt
                           Documents.

                                    "Permitted Precious Metals Agreements" means
                           precious metals agreements and arrangements (whether
                           styled as debt, a lease, a consignment or otherwise)
                           entered into from time to time by any Credit Party,
                           but only to the extent that the aggregate Dollar
                           Equivalent of the precious metals subject thereto
                           does not exceed $65,000,000. For purposes of this
                           definition, "precious metals" shall include, without
                           limitation, gold, silver, platinum, palladium and
                           copper (even though copper is not generally deemed to
                           be a precious metal).

         (b)      The definition of "Kazakhstan Contract" set forth in Section 1
                  of the Loan Agreement is hereby deleted in its entirety and
                  replaced with the following:

                                    "Beryllium Contracts" means any and all
                           agreements or other arrangements (however styled) for
                           the purchase, procurement or other acquisition of
                           Beryllium, in whatever form (including, without
                           limitation, Beryl ore, Copper Beryllium Master Alloy,
                           Vacuum Cast Beryllium Ingot and Vacuum Hot Pressed
                           Beryllium Billet), entered into from time to time by
                           any Credit Party, but only to the extent that the
                           Dollar Equivalent of any Indebtedness related thereto
                           does not exceed $20,000,000 during any consecutive
                           12-month period.

                  The foregoing definition shall be inserted in Section 1 of the
                  Loan Agreement in appropriate alphabetical order. Any and all
                  references in the Loan Agreement to "Kazakhstan Contract" are
                  hereby replaced with references to "Beryllium Contracts".

2.       Amendments to Section 5.2 of the Loan Agreement.

         (a)      Section 5.2(b)(viii) of the Loan Agreement is hereby amended
                  by deleting the text "$15,000,000" appearing therein and
                  replacing such text with "25,000,000".

         (b)      Section 5.2(b)(ix) of the Loan Agreement is hereby amended by
                  deleting the text "$1,000,000" appearing therein and replacing
                  such text with "5,000,000".

         (c)      Section 5.2(e)(iii) of the Loan Agreement is hereby amended by
                  deleting the text "$250,000" appearing therein and replacing
                  such text with "1,000,000".


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         (d)      Section 5.2(f)(7) of the Loan Agreement is hereby deleted in
                  its entirety and replaced with the following:

                                    (7) other Investments not to exceed
                           $2,500,000 each, and $7,500,000 in the aggregate
                           during the term of this Agreement; provided, however,
                           that the foregoing $2,500,000 limitation on each
                           Investment shall not apply and the $7,500,000
                           aggregate limitation for all Investments shall be
                           deemed to be $20,000,000 as long as Availability (as
                           defined in the Bank One Credit Agreement) equals or
                           exceeds $20,000,000 immediately prior to and
                           immediately after giving effect to any such
                           Investment;

         (e)      Section 5.2(f)(8) of the Loan Agreement is hereby deleted in
                  its entirety and replaced with the following:

                                    (8) Acquisitions in which the cash portion
                           of the purchase price does not exceed $2,500,000 per
                           Acquisition and $7,500,000 in the aggregate for all
                           Acquisitions during any Fiscal Year (it being
                           understood that there shall be no limit on
                           Acquisitions using common stock of the Borrower);
                           provided, however, that the foregoing $2,500,000
                           limitation on each Acquisition shall not apply and
                           the $7,500,000 aggregate limitation for Acquisitions
                           shall be deemed to be $15,000,000 as long as
                           Availability (as defined in the Bank One Credit
                           Agreement) equals or exceeds $20,000,000 immediately
                           prior to and immediately after giving effect to any
                           such Acquisition;


         (f)      Section 5.2(n)(ii) of the Loan Agreement is hereby deleted in
                  its entirety and replaced with the following:

                                    (ii) Fixed Charge Coverage Ratio. Permit the
                           Fixed Charge Coverage Ratio, determined as of the end
                           of each of its Fiscal Quarters for the then
                           most-recently ended four Fiscal Quarters, to be less
                           than (a) 1.25 to 1.00 on the Closing Date through
                           September 30, 2005 and (b) 1.50 to 1.00 at all times
                           thereafter. Notwithstanding the foregoing, as long as
                           Availability (as defined in the Bank One Credit
                           Agreement) is not less than $20,000,000 for 3
                           consecutive Business Days or any 5 Business Days in
                           any Fiscal Quarter, the Credit Parties shall not be
                           required to maintain or report to the Collateral
                           Agent or any other Lender the foregoing Fixed Charge
                           Coverage Ratio for such Fiscal Quarter.

3.       References to Export-Import Loan Deleted. All references to the
         "Export-Import Loan" and the "Export-Import Loan Documents" are hereby
         deleted from the Loan Agreement, and any provision of the Loan
         Agreement containing any such reference shall, as of the Effective


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         Date, be read as if such reference was not contained therein and be
         amended mutatis mutandis to accommodate such deletions in the context
         of such provisions.

4.       Representations and Warranties. Each Credit Party represents and
         warrants to the Collateral Agent and the Required Lender that: (a) such
         Credit Party has the power and authority to execute and deliver this
         Amendment; (b) the execution and delivery by such Credit Party of this
         Amendment, and the performance of its obligations hereunder, have been
         duly authorized by proper proceedings; and (c) this Amendment
         constitutes a legal, valid and binding obligation of such Credit Party,
         enforceable against such Credit Party in accordance with its terms,
         except as enforceability may be limited by bankruptcy, insolvency or
         similar laws affecting the enforcement of creditors' rights generally
         and except as the same may be subject to general principles of equity.
         The Required Lender represents and warrants that, as of the date hereof
         and as of the Effective Date, it holds greater than 50% of the
         aggregate principal amount of all Loans outstanding under the Loan
         Agreement, and the Required Lender and the Collateral Agent are
         executing this Amendment pursuant to Section 10.1(d) of the Loan
         Agreement.

5.       Effectuation. Upon the full execution of this Amendment and without any
         further action required by the parties hereto, the amendments to the
         Loan Agreement contemplated by this Amendment shall be deemed effective
         as of the Effective Date. There are no conditions precedent or
         subsequent to the effectiveness of this Amendment.

6.       Consideration. As consideration for this Amendment, the Credit Parties
         shall reimburse the Collateral Agent for its reasonable, out-of-pocket
         costs, fees and expenses incurred in connection with the review and
         negotiation of this Amendment, including, without limitation,
         reasonable attorney's fees.

7.       Continued Effectiveness of Loan Agreement. Except as specifically
         amended herein, directly or by reference, all of the provisions of the
         Loan Agreement are confirmed and ratified, and shall remain as
         originally written.

8.       Governing Law. This Amendment shall be governed by, and construed and
         enforced in accordance with, the laws of the State of New York
         applicable to contracts made and performed in such state, without
         regard to the principles thereof regarding conflict of laws.

9.       No Impairment of Security Interests. The parties hereto agree that this
         Amendment shall in no manner affect or impair the liens and security
         interests evidenced by the Loan Agreement and/or any other instruments
         evidencing, securing or related to the Obligations.

10.      Counterparts; Facsimile Signatures. This Amendment may be executed in
         counterparts and all such counterparts shall constitute one agreement
         binding on all the parties, notwithstanding that the parties are not
         signatories to the same counterpart. The parties may execute this
         Amendment by facsimile, and all such facsimile signatures shall have
         the same force and effect as manual signatures delivered in person.



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         [this space left blank intentionally -- signature pages follow]




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         IN WITNESS WHEREOF, the Borrower, the other Credit Parties, the
Collateral Agent and the Required Lender have caused this Amendment to be duly
executed and delivered by their respective representatives as of the date first
written above.

CREDIT PARTIES:

BRUSH ENGINEERED MATERIALS INC.           BEM SERVICES, INC.


By:                                       By:
   ----------------------------              -------------------------------
Name:                                     Name:
     --------------------------                -----------------------------
Title:                                    Title:
      -------------------------                 ----------------------------


BRUSH INTERNATIONAL, INC.                 BRUSH WELLMAN INC.


By:                                       By:
   ----------------------------              -------------------------------
Name:                                     Name:
     --------------------------                -----------------------------
Title:                                    Title:
      -------------------------                 ----------------------------


ZENTRIX TECHNOLOGIES INC.                 BRUSH RESOURCES INC.


By:                                       By:
   ----------------------------              -------------------------------
Name:                                     Name:
     --------------------------                -----------------------------
Title:                                    Title:
      -------------------------                 ----------------------------


BRUSH CERAMIC PRODUCTS INC.               CIRCUITS PROCESSING TECHNOLOGY, INC.


By:                                       By:
   ----------------------------              -------------------------------
Name:                                     Name:
     --------------------------                -----------------------------
Title:                                    Title:
      -------------------------                 ----------------------------


TECHNICAL MATERIALS, INC.                 WILLIAMS ADVANCED MATERIALS INC.


By:                                       By:
   ----------------------------              -------------------------------
Name:                                     Name:
     --------------------------                -----------------------------
Title:                                    Title:
      -------------------------                 ----------------------------


WILLIAMS ACQUISITION, LLC                 BRUSH WELLMAN (SINGAPORE) PTE LTD.


By:                                       By:
   ----------------------------              -------------------------------
Name:                                     Name:
     --------------------------                -----------------------------
Title:                                    Title:
      -------------------------                 ----------------------------


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                                             COLLATERAL AGENT:

                                             GUGGENHEIM CORPORATE FUNDING, LLC,
                                             as Collateral Agent

                                             By: /s/ Todd L. Boehly
                                                --------------------------------
                                                Todd L. Boehly
                                                Managing Director


                                             REQUIRED LENDER:

                                             HERAULT INTERNATIONAL, LTD., as the
                                             Required Lender

                                             By: /s/ Todd L. Boehly
                                                --------------------------------
                                                Todd L. Boehly
                                                Manager



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